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