Rainwater harvesting and green roofs

Over here in the Freerain sales department we are regularly asked about mixing green roofs and rainwater harvesting systems. It seems that many clients and their designers/consultants throw as many of the eco-technologies together in order to obtain their ideal sustainable development.  We are obviously not suggesting for one moment that this is bad thing.  But it is important to recognise that often the practicalities of the function and use of the building has to come first.
So can you or should you look to incorporate both a green roof and a rainwater harvesting system?

Rainwater harvesting - the requirements

Firstly, it is important to stress the basic requirement for a rainwater harvesting system to function and deliver a good quality of water.  Virtually all experts in this field (our competitors!), agree that a clean, traditional and pitched roof produces water which can be simply filtered to remove general leaves and grit type debris.  Flat roofs can sometimes have areas which drain very poorly and have "semi-stagnant" pools which only flow under more intense rainfall.  After all a rainwater harvesting system can only deliver the expected quality of water, if it is supplied with it in the first place.  The rainwater system isn't going to increase the quality and of course, a poorly designed/sized system could adversely affect the water.

Why are green roofs specified in the first place?

Green roof technologies have emerged in the last decade or so and add value to the function of a building in a number of ways.  Firstly, planning in certain areas of the country see them as a way of blending into an area, for example if the development is within a green space.  Secondly, the roof off rates are much reduced, by the plants holding on to the water, before transpiring it back into the atmosphere.  This also means that the often the lightest of rainfall would never reach the ground or the surface water discharge system.  This is important, as attenuation design can be reduced.  Finally, adding there must also be some carbon reduction from the plants themselves.

So can you combine rainwater harvesting and green roofs?

Green roof technology is improving all the time, in terms of stability of the sub-structure, the membranes and the overall understanding of the maintenance requirements.  This all helps to keep the resulting water clean and in some cases probably cleaner than some traditional roofs.  So, technically you can, but we at Freerain, advises our customers that the choice is really an "either or" situation.  The main reason behind that, is not as above (water quality), it is actually a much more practical reason.  The amount of water available to a rainwater harvesting system is about 90% for pitched roofs and around 75% for flat roofs.  For green (or even brown roofs) the amount is 40% at best. 
So for example, a 100M2 London roof (pitched) might send 52M3 of water to the tank per year.  But if it was a green roof, this would fall to only 23.3M3. 

We also recommend additional filtration to remove the higher organic load.  Even with the use of fine filtration, our expectation is that the resulting water might still be slightly dis-coloured.  Obviously, adding more kit, adds to the overall cost of a system.

Verdict/Recommendation

At Freerain we recommended keeping green roofs and rainwater harvesting separate, this is because the amount of water available to the rainwater system is much lower, there is an increased risk of lower quality water and finally, greater costs are associated.  Therefore, a system costs more, has a bit more maintenance and produces less water. 

Pre-design drainage issues with Commercial rainwater harvesting systems

Often pre-design or design errors make RWH difficult

In our technical department, they often complain that the drainage doesn't work when it comes to the rainwater harvesting system.  They bemoan the fact that a fall or any additional access chambers haven't been drawn on the drawings.  The also complain that the rainwater harvesting system has been ordered too late and much of the drainage has been already installed, making the rainwater harvesting very difficult to function.

An order arrives

As soon as Freerain Ltd accepts an order for a commercial rainwater harvesting system, we request a copy of the latest drainage drawings to check for the following:

• Water is running downhill (we've seen many drawings showing it going up!)
• A pre-tank filter has been drawn with appropriate falls
• The storage tank location has been marked
• Only traditional roof areas are being drainage and not open gullies, drains etc

Below is a generic drawing for what a typical underground rainwater harvesting system may look like on a drainage drawing. In this case no invert level has been specified and you can see the inlet invert is 0.  Of course on site that this is anywhere from 500 to 3,000mm down.

Problems

As mentioned above there can be a number of issues and problems with getting a rainwater harvesting system to work within a commercial application.

• Drainage built with a fall for the rainwater harvesting system
• Fall in the pipework not accounted for
• Not all the intended roof is sent to the tank
• Open gullies and non-roof areas are drained into the tank

 Much of the above is really because of two reasons.  Firstly, the rainwater harvesting system is ordered/considered too late and secondly, the consultant for the drainage hasn't appreciated the requirements of the rainwater harvesting system.

Summary

Rainwater harvesting for commercial buildings and projects should be relatively easy to install, but all too often not all parties in the planning stages come together.  Therefore, on many occasions the late consideration or the lack of planning leads to costly work-arounds on site and on a few occasions this has led to already built drainage being ripped up and re-laid as required to incorporate the rainwater harvesting system.

Hose pipe bans and British made underground tanks

So after two dry Winters, the UK is facing water restrictions, affecting areas from the South coast right up to parts of Yorkshire. The last similar ban was back in Summer of 2007, when the Southern water companies issues hose pipe bans.

Some fact!
Water companies in England and Wales leaked more than 3.3bn litres a day in 2010/11, according to the regulator Ofwat.
Demand for water stands at around 17bn litres a day, according to industry body Water UK.

It would seem that the UK climate has changed over the last 20 or 30 years, with more extreme weather, since 2007, there has been a number of high profile flooding events and the focus on the management of water had shifted from water supply to the control of surface water run-off. In reality both of these issues are never going away and should be tackled together. Short terms views on either will never solve the overall problem of water management in the UK. When the hose pipe bans were announced during early March, much of the media started talking about the need to create some sort of "national water grid" in other words move water from areas where it is plentiful to essentially the South and South East. This would potentially mean an awful lot of civil engineering, at quite an environmental (and carbon) cost. There doesn't seem to be a proper debate that includes rainwater harvesting.

Taking a more local approach would seem a better option, providing there is enough water available. Rainwater harvesting as many of you know has emerged during the last 12-15 years in the UK, brought over largely from Germany. Importing storage tanks from Germany has always been one of the main criticisms aimed at rainwater harvesting.

Freerain's parent The Gusto Group has tackled this very issue by investing in a rotational moulding factory and purpose rainwater harvesting designed tank moulds. The range of underground tanks include the following features:

1) 1800 litres up to 10,000 litres
2) Single piece, no need for messy on site assembly
3) Made from virgin high strength polyethylene.
4) Installed without the need for concrete back fill or bases
5) Supplied with telescopic access shaft and pedestrian cover.

www.gustotanks.co.uk

Freerain is obviously a customer of the Gusto Group storage tanks and have a number of different control systems built around them available. Garden rainwater harvesting systems are proving very popular at the moment, as customers look to store significant quantities of water for garden use and "beat the hose pipe ban" Find the garden rainwater harvesting systems here.
Garden rainwater harvesting can be a very good way to get involved with collecting rainwater, as trying to re-plumb a house to serve toilets and washing machines to an existing can prove difficult.

Remember you can use a rainwater harvesting system in the garden with a hose pipe, providing the water company imposing the restrictions haven't supplied the water.

Garden Rainwater harvesting

The Rain King 1000

With the onset of Summer and the news that we are facing water restrictions, not to mention brown grass! At Freerain Ltd we have been busy sending out one of our best selling products, The Rain King 1000. This is a basic, very DIY friendly due to the ease of the tank being hand-dig-able, but still a large enough volume to make a real difference compared to normal above ground water butts.
As part of the packaged the Rain King 1000, includes a 1,000 litre underground polyethylene storage tank, a downpipe filter and a stainless steel submersible pump. All this delivered on a pallet for only £869 (as June 2011). See garden rainwater harvesting for more information.

There are also storage tanks from 1800 right up to 10,000 litres with internal pre-tank filters for gardeners wanting even more water. These are also pumped systems and manufactured in the UK!!!

Above ground rainwater harvesting

We also appreciate that it is not always possible to bury a rainwater harvesting tank and so we also have a wall tank system, these are 800 litres each, so around 4 times the capacity of the traditional water butt and can be linked together to make really serious sized systems. Each system includes a tank, down pipe filter/diverter, a sight gauge and a pump. All the necessary inter-connecting pipes are included. See above ground rainwater harvesting for more information and current pricing.

We have received an so many enquiries from people who have been using water butts for a long time, and now realise that over the last few years, these are simply not large enough to last through significant periods of low rainfall. Also, when it is dry and hot, often this can be broken up by a heavy thunderstorm. We really need to intercept this and store it. Meaning that unless a decent amount of capacity is available, this opportunity will be lost.

Warmest April on record 2011

It has been reported this week that April 2011 (UK) was the warmest on record and figures out today shows that rainfall in most parts of UK were very low indeed. The south coast have received about 3-5% rainfall that they would have expected for April. Parts of Scotland were the exceptions with slightly above average, but only by a few percentage points.

The BBC are reporting that following a dry March as well, in terms of agriculture we could see food prices rise due to either lower yields and/or due to the cost associated with irrigation. This of course raise many questions, questions that are really beyond this post and indeed this blog.

We at Freerain have seen a massive increase in the number of potential customers looking for solutions to their water shortage issues. These range from the typical home gardener, who's traditional water butts ran out during the first weekend of April (if they lasted into April), to the small-holding needing a regular supply in larger quantities. We have also received enquiries from the leisure industry, for example pine lodge parks, these are often in slightly remote areas and need water mainly for irrigating their plants and in some cases washing down of the lodges themselves.

One question which is often aimed at rainwater harvesting is "if doesn't rain, what's the point of putting a tank in?" Which if you think about that, it is true. However, these dry spells (or actual drought conditions) are not rare events. Virtually every year we get similar stories in the news about lack of rainfall, coupled with increased demand (especially in the South East). Water shortages are not going away. So our customers are right to look to finding a solution not necessarily for their immediate problem, but for the next dry event.

In our office, we have been using rainwater harvesting to provide WC flushing and the occasional car washing function for about 12 years now and in that time we have seen many very dry spells. These are often combined with heavy storms in the middle of the hottest weather. These high rainfall events, fill the tank very quickly, which gives the office a supply for the next three weeks.

As mentioned above, garden watering is a hot topic (pardon the pun!) and it is much easier to install a system for gardening. This is because the is no requirement to change the household plumbing. Also, often the whole roof is not required meaning that the drainage also doesn't require substantial alterations. Our most popular systems are the Rain King garden systems. With the easiest of all and the most cost effective being the Rain King 1000.

For advice on garden rainwater harvesting and indeed full domestic systems, please visit our website Freerain or call 01636 894906 sales@freerain.co.uk

Water shortages again in the news

Well it's been the driest March for about 40 years for most parts of the UK. Already here we are in the 3rd week of April (2011 and there are stories in the news appearing about the water levels in our reservoirs.

The BBC has reported earlier this week that some of the reservoirs are currently at around 80% of the expected levels for this time of the year. But didn't we have a decent amount of rainfall over the winter (including the several bouts of snowfall)? So one dry month and the country seems to start running out of water.

Does this mean that we are in fact living beyond our means for water, especially with a drier climate predicted and an ever-increasing population?

This hightlights the need for a water strategy and one which embraces all available techniques, from water conservation right throught to localised capture/collection. Obviously we at Freerain are very focused on rainwater harvesting and we have seen from our own monitoring that a typical household can reduce their mains water demand by 50%. But also there is a need for education at various key levels to ensure that water is used carefully.

There has been some debate over the years surrounding the carbon cost of rainwater harvesting, but it must be stressed that a small amount of carbon is more than worthwhile to keep the taps flowing. Again, rainwater harvesting must be used together with various other techniques as part of an all round effort.

At Freerain we have recently launched a new range of UK manufactured rainwater harvesting tanks to further reduce the environmental impact of similar German imported tanks. These tanks can be used in domestic and smaller commercial applications. They start from 1,800 litres right through to 10,000 litres, all single piece and all have a very low profile. Being made from polyethylene and designed to be installed in very high water tables, they can be installed without concrete bases, backfills or surrounds. Domestic rainwater harvesting tanks

First a hose pipe ban and now canal issues

There is much talk in the industry regarding payback rates, carbon footprints and reliability issues with rainwater harvesting systems. Yet the real issue is the security of the national water supply. We have been far too relaxed over the last century, mainly thanks to the Victorian engineers, driven on by the industrial revolution. Also our perception that the UK climate is wet and therefore water is not a resource, it merely comes out of the tap anytime we turn it on. With an ever-increasing population, possible climate change, evidence is pointing towards more pressure on the most basic of resources.

In recent weeks we saw the start of the first water restrictions in the UK for four years and it was actually very surprising to see it not in the South East, but the North West. Whilst this is more of a pain than a real issue, it points to a potentially greater problem. A single dry season has been enough to stress the supply. Just this week we have seen further evidence of the environmental impact of an over-stressed water supply. As reported by the BBC there are closures of canal ways due to the lack of water, see here The Leeds-Liverpool canal is one of the major parts of the network. Not only does this imply the environmental concerns, but also the impact on tourism and the economic situation.

Also this week, people in the midlands are being asked to conserve water, to avoid a mandatory ban. See here, also from the BBC.

So when the issue of rainwater harvesting is being considered is simply not enough to consider it as a stand-alone solution for a single dwelling, project or even a larger site. Does it really matter that it might not payback in less than three years? Well certainly costs are important and nobody is suggesting otherwise, but maintaining supplies through the use of rainwater harvesting and other water conservation measures.

www.freerain.co.uk

Hose pipe bans on the way

Water, water everywhere, but not a drop to spare....

No doubt you will have seen in the national press a story concerning the North West of England and the mounting concerns regarding water restrictions. It is very likely after a dry spring season, that hose-pipe bans and perhaps reduced water pressure could be in place shortly. Also, we have seen the warmest weekend of the year, following an above average temperature week.

For me this highlights the need to conserve our most basic of resources, what we are saying here is that, an above average rainfall region becomes water stressed, by one dry season. What is likely to mean, if the population growth figures are true and the affects of "global warming"?

Already at Freerain Ltd, we have seen a dramatic increase in enquiries from all areas of the UK and not just the North West. The gardening rainwater harvesing systems, Rain King, allow easier retro-fitting of a rainwater system, as they don't require changes to the internal plumbing arrangements.

UK Water Bills could rise

Background/Introduction

The most basic requirement in the UK, namely water is seriously under threat. Yet in this country we seem to be fairly blinkered into the carbon only argument in terms of our sustainable approach. Yes, carbon is a very important subject and measure of our environmental progress, but I would argue that it cannot and must be not used as the only measure.

With the UK's population set to increase by potentially 20 million more by 2050 and shifts in our climate (yet to be fully understood and determined), all resources will come under unprecedented stress. Added to this the current stress levels on water supplies in the South East of England, water conservation is a must.


Water of course is not only required for the most basic function, namely drinking, but it is fundamental to our crop growing and agricultural strategies. Recent studies have indicated that the availability of suitable growing conditions in the future maybe restricted to the wettest parts of the UK, i.e. Wales, Scotland and parts of the South West. Meaning that the traditional cereal regions, such as East Anglia and Lincolnshire would be lost from production. Yet more resource stress.



Planning



Strategic level planning for water is centered on the extra people and the dwindling (expected) rainfall predictions. So less water for more people. Currently in the UK we "enjoy" an average of 150 litres per person per day, more in certain areas of the country, the South East. The Code for Sustainable Homes (CSH) aims for a reduction to 80 litres per person per day at code level 5 and 6. For many this would be a complete change to their way of life. Potentially ending "taken-for-granted" activities, such as a full bath or nightly garden watering etc.



Rainwater harvesting - a solution



In the UK we have been fairly slow to adopt rainwater harvesting, this in part is due to the lack of financial incentives. In Germany, where rainwater harvesting is widely used, the cost of water is significantly higher than here in the UK. Lack of grants for rainwater harvesting, such as those enjoyed by other technologies, such as Solar, has made it difficult for business and individuals to justify the expense on paybacks alone.
Better technology, the recently published BS8515:2009, improved supply chains, installers and understanding will help to reduce the overall cost of installing a rainwater collection system.

However, a warning from the water companies suggests that the cost of water is moving up and one report recently in the Daily Mail suggests 27% above inflation.

http://www.dailymail.co.uk/news/article-1267821/Water-bills-soar-industry-unsustainable-firm-warns.html

Housing Association opts for a communal rainwater harvesting system

Intro

Freerain Ltd has recently supplied a communal rainwater harvesting system to Two Rivers Housing Association at their Turley Court site in Cinderford, near Gloucester.
The system supplies ten dwellings with collected rainwater from the roofs to supply WC flushing and an outside tap.

The System

13,000 litre underground storage tank
Freerain DUO204 control set
2 submersible pumps for duty/assist
Full mains top-up

It is estimated that the system will provide 265M3 of water per year, providing a financial saving and helping to reduce the overal environmental impact of the site.

The site also has an extenive range of other environmental measures, which enabled it to reach the Code for Sustainable Homes Level required.

This site is of particular interest as due to the design of the houses a header tank system for rainwater harvesting control system wasn't possible. Normally where dwellings share a collection tank, each dwelling uses its own secondary tank.

Rivers may run dry

Recent press reports have again highlighted the pressures on national water-supplies and the consequences if steps are not taken now to reduce consumption.

All the main national newspapers have now carried articles outlining the likely effect on national rivers if water continues to be extracted at current rates; within a relatively short number of years substantially reduced summer flow-rates are predicted.

Alongside this scenario, the press have also been reporting that the fitting of water meters is to become mandatory. Water meters are shown to play a useful role in reducing mains water consumption, although some claim that this can have a unfair impact on the poor.

So far, articles such as the above have failed to draw the link between reducing national mains water consumption, and the widespread introduction of rainwater harvesting, which reduce domestic consumption by around 50% without any adverse social and environmental effects.

Use for commercial and industrial applications, this mains water saving can rise to in excess of 80% on any building that combines a large roof, with a high demand for non-potable for applications such as toilet flushing, clothes washing and outside use.

British Standard for Rainwater Harvesting Systems

The recent publication of British Standard 8515 for rainwater harvesting systems, available via http://www.bsigroup.com/, establishes for the first time a yardstick against which systems being supplied in the UK can be measured.

Harvesting rainwater to supply household needs is one of the oldest and most durable forms of supplying water worldwide, although until recently practiced in the UK mainly in the context of garden irrigation, following the introduction by the Victorians of mains-supplied water.

Due to modern lifestyles and population growth, however, UK mains water supplies are now coming under varying degrees of stress – particularly in England south of the Humber where the stress is generally severe (see Environment Agency map).

This is reflected in the mains water consumption requirements set out in the Code for Sustainable homes, and commercial equivalents such as BREEAM assessments. Up to a point, these requirements can be met by economising on water use, but if lifestyle (baths and showers etc) is not to be compromised then substituting recycled water for mains water becomes necessary.

The easiest and most cost-effective way of doing this is to use harvested rainwater instead of mains water for non-potable uses such as toilet-flushing, clothes washing machines, car washing and irrigation. This reduces mains water consumption by around 50% in the home and by more than 80% in any building that combines a large roof with a high demand for non-potable water.

BS 8515 now sets the standard for how systems as a whole (see schematic diagram) and components within the system should function. Very simply, the aim is to route the rainwater falling on the roof to a storage tank, filtering it beforehand to remove any solid impurities. When needed, the water is then pumped (directly or via a header tank) to its point of use via pipework dedicated to non-potable water.

From the users perspective, using rainwater in this way is indistinguishable from using the normal mains supply, with the associated controls automatically controlling all functions and ensuring, using a mains water backup when needed during prolonged dry spell, continuity of supply.

Water Charges set for inflation busting rises

Introduction

Previously agreed water charge increases come in to affect from 1st April 2009. This was agreed sometime ago and it is 1.1% above the latest inflation rate, currently 3%. Ofwat have suggested that this should increase the average water bill by £13 per year. Some water companies such as South West Water are increasing their prices by as little as 0.9%, but they do currently have one of the highest tariffs.

More on the way

Ofwat are currently developing the pricing strategy for the years 2010 to 2015. During uncertain economic times, clearly this is a very difficult balancing act.

Reasons for the rise

There are a number of factors which have been considered in determining the level of money needed to improve or maintain the level of service. We have been very fortunate in the UK that we developed a world leading water network, but this pioneering period has left the UK with an aging network of both water supplies and sewerage.
There is also increased demand in certain already over-stretched such as the South East of England. Several articles have suggested that this area has less water per head than parts of Africa and this highlights the need to maintain the network. For some years now, we have heard of massive leak rates directly resulting from old pipes.

What else can be done?

Clearly investment is needed and will always be, but this must go hand in hand with other water measures. The Code for Sustainable Homes tackles this issue for new-build domestic homes, but there is little incentive to make water saving measures for the current housing stock. New-build accounts for maybe 1%.
Individuals can take steps to reduce their expenditure on water, some of these are listed below:

1) Aerated taps
2) Aerated shower heads
3) Smaller baths or filled to a minimum
4) Rainwater harvesting (suitable for times of renovation or a simple garden system)
5) Displacement of WC cistern volume with a brick or bottle filled with stones.

There are plenty more ways to reduce water in the home. But obviously, should any of the above measures be taken, the property should be metered and not on a rates or fixed charging structure

Rainwater harvesting tanks: Do they need cleaning?

Introduction

Rainwater harvesting systems are becoming increasingly popular, and the fact the Freerain's early customers have had their tanks installed since 1999. Many people are considering the long term effects and issues concerning older rainwater harvesting systems.

Cleaning?

The general water quality and effectiveness of a rainwater harvesting system is largely dependent on the size of the storage tank installed. Too large and it may never overflow and turn the water over enough. Too small and it doesn't store enough water to be effective and the dwelling/project is reliant on mains water top-up.

Assuming the storage tank has been sized correctly, then it should overflow a few times a year, assuming the system includes a calming inlet and has a suitable pre-tank filter, then the tanks really shouldn't need cleaning. The heavier particles should be removed by the leaf and grit pre-tank filter, the finest particles should float and be skimmed off during overflow. The particles in suspension eventually get sucked up by the submersible pump and are then removed by the inline strainer/carbon filter or whatever has been included on the system.

So a well designed system is very unlikely to need cleaning out, but there is one big assumption, this assumes that only roof water has been sent to the system. Water from hard-standing should not be sent to the rainwater tank, nor should water from a green roof system. Although newer green roof systems do filter the water very well. The overflow from the storage tank should also be protected from backing up. In other words, a well designed system, being used in a normal way, should NEVER need cleaning.

Germany

In Germany rainwater harvesting is about twenty years ahead of the UK and their experience is exactly as described above. Only poorly designed or mis-used systems require major maintenance.

Roof top rainwater storage, does it work?

If you think of a traditional rainwater harvesting system, in the UK and most of Europe. Then you would probably think of an underground storage tank, a physical filter before storage and a pumping system. We have previously looked at the options for controls and this is broadly two types. The direct pressure system and the header tank system, being fed from the underground tank.

We at Freerain Ltd, are asked quite often about the option of eliminating the underground storage tank and diverting roof water directly into a header tank. On first thought this seems like a good idea, no excavation, no underground tank and maybe even no pump!! All sounds pretty good?

Domestic system, we need storage of around 800-1,000 litres per person to make the rainwater harvesting system effective. So a 4,700 litre system when full would weight around 5 MT!! and take up a considerable amount of space. In order to strengthen the floor, it could be very costly and indeed more than a non-concrete underground tank installation. (as per Freerain tanks). We have also previously discussed the fact that the water should remain dark, cold and not subjected to thermo-cycling (that is rapid heating and cooling). Whereas inside a building it might be. Finally, the overflow from storage would need to be designed to never flood the building at times of heavy rainfall.

Commercial systems are more likely to be specifically designed to take the weight, if underground or above ground outside is not possible. But internal sectional storage tanks do tend to me more expensive and take up valuable space.

Filtering the water prior to the storage tank can sometimes be problematic. A traditional underground system utilises gravity to move the water from the roof, through/across a filter and finally in to a storage tank. The rainwater filter is normally either housed in the tank neck (as with Freerain domestic tanks) or externally for larger commercial systems. So if you want to have a high-level storage tank it must be designed to be able to accommodate any invert drops across the filters and the overflow.

In summary, for domestic projects we wouldn't consider it as a viable option, too much weight or too small amount of water stored. For commercial projects it is always an option, but only if underground or above ground external has been considered and rejected first.

Rainwater harvesting and water restrictions

Question: I've got my rainwater harvesting system installed, should I worry about hosepipe bans and other water restrictions?





Answer: You need to be aware that most rainwater harvesting systems are in fact ultimately connected to the mains water supply. Therefore, you can use water from a hose, providing the local water company (imposing/enforcing, the restriction) haven't supplied the water.


We at Freerain, routinely supply systems without a mains top-up specially for external/garden rainwater harvesting This ultimately protects the customer from any grey areas or mis-understandings. Quite simply, if the hose/sprinkler has water, its rainwater, if not the tank is empty!!!

For the latest information about hosepipe bans and general water restrictions, I would recommend visiting Hosepipeban.org.uk There you will find links to the water authority sites, water saving tips and a forum.

We may not have had any major water restrictions in the UK for a few years, but with a population increase and the effects of climate change, we are certain to have more water stress.

Another solution

Where rainwater harvesting systems are used for both internal and external demands, a mains top-up is essential. Direct pressure systems (whereby the water is supplied a pump pressure) mains water must pass through a class AA air-gap (see WRAS) to avoid any cross-contamination between potable and non-potable water. The easiest way is to top-up the external (underground) storage tank with mains water at time of low level. This then raises the possibility of a hosepipe supplying mains water on to the garden. Which during a hosepipe ban would make the system fall under the ban. One water to remove this is to install a header tank (break tank) in the property. This way, pump pressure can be sent to the outside tap directly. But all the mains water topping up occurs in the the header tank. So, the only water to pass through a hosepipe would be the locally collected rainwater.

Suitability of rainwater harvesting systems for existing dwellings

Domestic rainwater harvesting systems are generally aimed at new-build.
There are several reasons for this and these are:-

• The drainage can be designed specifically with the rainwater system in mind.
• The way the internal plumbing is arranged differs slightly to separate out the potable and non-potable pipe work
• It is often easier to move the tank around the site before the building is completed.
• Excavation machinery is already available.

The costs associated with installing a system are reduced by the above factors, making them more affordable.

When considering an existing property is can be very much more expensive, starting with the fact that VAT is added to the system price. This is currently 15% (recently 17.5%). But moreover, re-routing pipe work can be very expensive and can involved fairly major cosmetic works. The external drainage is often difficult to access, either due to hidden pipe runs, unworkable invert depths and/or unknown modifications.

It can also be difficult to get the tank to the desirable location around the property. For example a semi-detached house, has only access around one side. Often this is limited. So a crane cost must be added to the project.

Space in the garden can also be an issue, as digging close to foundations can be risky and require a professionally appointed structural engineer to advise on the works.

So, with the extra costs and the fact that water is actually still relatively cheap in the UK, there isn't the financial incentive to harvested the rainwater.

At Freerain, we advise customers with existing properties to consider a system for external/gardening use. This is because the internal plumbing is changed and perhaps not all of the drainage is needed to be centralised. This reduces the costs significantly, but of course not everyone is satisfied with external water only.

For commercial projects, these are reviewed on an individual basis, this is because the very nature of some of of the sites. External drainage can sometimes be very easily accessed, above ground tanks are more acceptable and work technically better.

In summary, rainwater harvesting systems are best suited to new-build projects for domestic dwellings, but perhaps commercial sites can with certain modifications incorporate a system.

Is Legionella problem for rainwater harvesting systems?

Introduction

Legionnaires' disease, or Legionellosis is an infectious disease caused by a genus of bacteria. These bacteria thrive in warm conditions typically between 25-45oC. There are several types of Legionellosis, but for the point of this blog we are only going to cover the most common type. The condition is much like severe pneumonia and can be fatal. The first and still the most famous outbreak was in 1976 in Philadelphia, where it was given the name Legionaries disease. A gathering a war veterans were together for an annual event, see here. In the UK cases are rare, mainly due to the strict regulations now in place, but in 2002 there was a case where 7 people died and about 170 contracted the condition from a nearby cooling tower.

It is estimated that around 10,000 people die from the condition per year in the USA.


Legionella bacteria: Conditions for growth


The bacteria thrives in a range of temperatures between 25-45oC, but does indeed survive at lower temperature, but is dormant at around 20oC. As with most bacteria it requires a moist, if not aqueous environment. So the focus for the regulations has been centered around hot water systems, such as showers, heating and hot tubes. But also ventilation systems, whereby water is used as the indirect heat source.


Pathway and transmission


Infections normally occur through the respiration system in the form of fine spray (aerosols) and so it not the water body itself. Therefore spraying, minor leaks in ventilation systems and bathing or the areas of special concern.


Rainwater harvesting systems, are they a potential risk?


A well designed rainwater harvesting system is designed with the quality of water in mind and this is usually dominated by the tank size. Sizing the storage correctly ensures that the water is not stored for too long (around 20 days) , but balancing the need to supply water. Generally speaking in the UK, we don't have very long dry periods, but you might be surprised to learn that on average we receive significant rainfall about every two and half weeks. Therefore, storing very small quantities (relative to demand) is not efficient and in many ways pointless.

In the UK the rainwater tanks are normally underground and include a pre-tank filter. This helps in several ways. Firstly, being underground the temperature is no more than about 10oC even during mid-summer. Secondly, the pre-tank filter removes much of the organic matter and this prevents the build-up of bacteria generally. It is also dark. So the water is kept cold and dark and in many respects clean. Many systems use calming inlets to the tanks. This helps to retain higher than normal oxygen levels, promoting healthly aerobic bacteria. See the Environment Agency for more water quality discussions.

In certain commercial applications such as schools, we at Freerain advise the use of ultra-violet sterilisation unit. Whilst it is not part of any regulations, we feel that it is a belt and braces approach to rainwater harvesting. Especially where the project utilises a header tank type system. That is a secondary storage tank at high level. This is because of the usage pattern of a school year. There could be several weeks during the year, where water could be sat in the header tank. We are not saying that there is any risk of legionella at all, but many consultants and specifiers are not prepared to include a system without a UV unit.

Another application for adding a ultra-violet unit is for irrigation systems, where there is the chance that rainwater could be sprayed as an aerosol. Also, the water is often kept longer as water quality is less important. Finally, some are above ground tanks. Adding the ultra-violet unit again is not part of regulations, but it is a cheap option, sometimes costing as little as £400.


Summary


Rainwater harvesting systems are not a source for legionella bacteria to thrive, due to the conditions the water is kept. That is much colder than the lower limit for growth as researched by the Reliance Worldwide organisation. The water is generally clean before it enters storage and used quickly before it deteriorates.
The focus is quite rightly on hot water systems and not cold rainwater systems. Care should be taken, but a well designed system from a well respected supplier/designer remains important.

British Chamber Awards 2008

Freerain took a party of four to the British Chamber Awards 2008 dinner hosted by Sian Jones and Dermot Murnaghan.

The awards were held in the fantastic venue, the Natural History Museum. There were approximately 550 people from all over the country from sole traders to multi-national comapanies.

Freerain were nominated in the Green Business category having previously won the regional round a few months previously. There were in total seven companies in total representing the Nottinghamshire and Derbyshire chamber this year, across the various different categories.

Unfortunately, we didn't win the award, but it was a great pleasure to be nominated and clearly shows how the hard work by all the staff is really paying off.

The green award was one of the most competitive of all of the awards and this clearly demonstrates industries comittment to environmental issues.

East Midlands EXPO 19th November 2008

Freerain Ltd is attending the East Midlands EXPO event at the Lincolnshire Showground's Epic Centre. The venue was chosen due to its environmental and sustainable creditials.

The event is free to enter and open to the general public to gain an insight in to the latest environmental trends and products and also attend the many seminars delivered by a number of professionals.

The centre, sometimes known as the Epic Project was a purpose built exhibition centre with a whole host of sustainable technologies. Indeed Freerain supplied the rainwater harvesting system and this was installed by local contractor Sleaford Building Services (SBS Ltd). Other technologies included wind turbines, biomass heating, solar and PV. Along side the technologies were traditional construction methods, including the use of natural ventilation, minimal use of steel and concrete. With a general focus on a sustainable approach to construction.

The rainwater harvesting system supplied was:

18,000L GRP underground storage tank
VF2 Filter roof filter
Duo-204 control system (two submersible pumps)
Expansion Vessel
UV Filter