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

Rainwater Harvesting: Oak Tree House

Oak Tree House in Knaphill, Woking is a three bedroom detached house that has been refurbished as a show house, for local people to gain an insight in to how they might reduce their own domestic energy and water usage.

The project was completed by energy partner ECSC, building partner Mansell PLC and Environmental partner, Woking LA21, Woking Borough Council in November 2008.

The project covered several aspects of sustainable living and these included:

Sustainably sourced furnishings
High level of insulation
High-efficiency boiler and heating controls
Solar thermal hot water
Solar PV
Passive solar harnessing
Rainwater harvesting
Water conservation measure, such as aerated shower and aerated taps.
Drought resistant plant species in the garden

Freerain Ltd, supplied a 3,500 litre rainwater harvesting system to the project.
The system which retails at around £2,200 + VAT (supplied only) includes a tank, submersible pump and a control package. This system also draws mains water when there is insufficient rainfall automatically. Therefore the homeowner doesn't have to do anything, but a simple filter clean about four times per year. Should the house receive average rainfall for the area, the system could provide up to 70M3 of water during the year. This means that the water use for the house with an average family will broadly halve.
The collected water is non-potable, which is suitable for WC flushing, washing machines and all outside tap functions. Along with permeable paving, the rainwater tank will help to prevent localised flooding issues, that are often associated with urban areas.

The house will be shortly open to public as a demonstration property.

Ultra-violet sterilisation as an upgrade for a rainwater harvesting system

Background

A rainwater harvesting system (sometimes wrongly called a grey water system) can be defined as a system which collects roof water for use as non-potable water. Much is written on the Internet and talked about with rainwater harvesting (recycling) systems about the use of ultra-violet sterilisation as a means of sterilising the water. Typically a rainwater harvesting system will have a physical "leaf and grit" type filter or filters. This is perfectly good enough to clean the water for uses such as WC flushing (accounts for 25% of daily water consumption), washing machines and outside taps. It is possible to upgrade the water to fully drinking (potable) standard. A good upgrade should also include a fine filter prior to the UV unit. The filter needs to be reducing particles smaller than 5 microns. This is because of the "shadowing" effect. This means that should the particles be greater than this, then bacteria and pathogens can be shielded from the UV light source. This finer filtration is often in the form of carbon filtering, and usually in sealed purpose made cartridges.

Potable upgrade or not?

So, it is possible to upgrade the collected water from a rainwater harvesting system, but is it actually worth it? From the paragraph above, you can extra equipment is needed to the rainwater recycling system. This can cost from around eight hundred pounds. With consumble carbon cartridges and a mains power operated ultra violet sterilisation unit, these have a running cost of around two hundred pounds per annum. Which in some circumstances is perfectly reasonable. For example, if a dwelling is off-grid by the remoteness of the site, then a private water supply is very desirable and a running cost like this is very affordable. But where mains water is freely available, and the householder is looking for savings or to be more environmentally responsible, then perhaps this type of upgrade is not worthwhile. As the manufacture of the UV bulbs, equipment and carbon filters contributes to industrial environmental damage. The extra power to use the system and the fact that mains water is already available, makes for a strong environmental case against upgrade, but using a rainwater harvesting system to supplement mains water and in most cases halve the amount used is a much more compelling case.

Quick calculation

Let's take a 150M2 roof in Surrey, 3 bedroom house with 4 people living in it.
The property might collect around 95M3 of water per year. The demand that could be fufilled by rainwater would be around 66M3 per year. If this project was to be upgraded to fully potable (drinking) standard, then the property would be using around 132M3. So, in this case there wouldn't be enough water to meet the demand. So, depending on which type of rainwater recycling system was installed mains water might be re-treated. This is because a direct pressure system tops up the external storage tank with mains water at times of low rainfall (or high demand). Making the idea of installing the potable upgrade not worthwhile.

Commercial rainwater harvesting system

Many commercial specifications include UV sterilisation units, this is not due regulations, but more because the client "decides" it's the thing to do. Often encouraged by industry professionals, using their experience of hot water systems. Legionnaires' disease is often mentioned, but this is only a problem where the water is held at temperatures over 25 oC. Rainwater stored underground is very unlikely to ever reach those levels. So it's not a problem, but in a £30M project a few hundred pounds is a very easy belt and braces approach for specifiers.

Rainwater recycling: Types of control systems

Background and introduction

Rainwater recycling or rainwater harvesting as it is more commonly known is a fairly well mature technology that was developed during the last thirty years. Essentially the storage and filters quite simple. But the control systems are more complex driven by the need for reliability. In the UK, we have mostly thanks the Victorians enjoyed a safe and reliable water supply for the last hundred years or so. It's really in the last fifteen years where terms such as water stress has started to be used. The Environment Agency suggests that everywhere south of the Humber estuary is under some form water stress and of course the drier south and south east is continuing to see an increasing population.

Types of controls

There are three main catagories of controls with most rainwater harvesting systems.

1. Direct pressure systems
2. Header/break tank systems
3. External use only (Gardening) systems

Direct pressure

Direct pressure systems work by supplying water at pump pressure directly to the point of use via a control panel. This panel also controls the mains water back-up arrangements, of which there are a number of different configurations between different manufacturers. But all systems must comply with WRAS regulations and this put simply here is concerned with an air gap (type AA) to eliminate direct contact between potable and non-potable water. There are also regulations regarding pipework identification.

These systems are normally installed in lower demand situations such as domestic single dwellings. Where the demand is much higher, more than one pump can be used as duty standby assist type arrangements.

Header/break tank

These systems differ slightly from the direct pressure systems as the main pump or pumps send the water to a header tank (gravity system) or to a plant room based break tank. Where required additional pumps are used to boost the water supply around the building. These types of systems tend to be used in more commercial/industrial projects. Similar water regulations also apply to these systems and a slot/ cut-away (AB type airgap) is also required.

Garden rainwater harvesting

These systems were developed in response to the hose-pipe ban/water restrictions that were in place arouns 2006 (UK). They tend to have a lower specification generally, and most importantly the mains water top-up arrangements are usually excluded to protect the end user from falling foul of the water restrictions.

At Freerain Ltd, we have developed numerous various on the themes above to suit the project requirements and indeed are contuning to develop new ways to improve the performance and interface with BMS systems and other systems. More information about commercial rainwater harvesting system can be found on our website.

Rainwater harvesting: Millennium Green case study

Gusto Construction Ltd, completed a development site of 24 houses in 1999. Each property on the Millennium Green site was built to a standard far beyond the building regulations and achieved the status of Eco-Excellent. Each property was fitted with a Freerain rainwater harvesting system to meet the water reduction targets. Most of the plots were fitted with a 3,500 litre or a 4,700 litre storage tank, depending on the size of the plot. The system uses a submersible pump to deliver the stored rainwater directly in to the property, without the need for a header tank. The resulting water is suitable for WC flusing, washing machines and outside tap functions. The water is not suitable for drinking or bathing, as this water is non-potable (sometimes called reclaimed or even greywater).

During the year 2001, the Environment Agency and Severn Trent Water carried out a study on one of the plots at Millennium Green to see the progress of the rainwater harvesting system (sometimes called rainwater recycling). They looked at various aspects, including reliability, water quality and amount of mains water was displaced. The weather pattern for the year was not unusal and certainly could be considered an average year.



The above image (available on the main title link in a larger form) shows the level of water in the storage tank day by day. This showed that on a few ocasions a few litres of mains water was added to the storage tank. This is very beneficial as mains water has certain chemicals in it, and the free chlorine does help to maintain the freshness of the water.

Also several times during the year the tank overflowed, which a well designed rainwater harvesting system should do. This allows for any scum layer and suspended particles to be washed. With the Freerain system, the pre-tank filter is housed in the neck of the tank, this allows for the overflowing water to back-wash the filter. Thus reducing maintenance and maintaining water quality.


The study also monitored the amount of water used in the property and the above figure shows the daily percentage split between mains water (in blue) and the rainwater (in grey). The split was almost 50% of each. So when considering the Code for Sustainable Homes you can see that a reduction in mainswater consumption of 50% would mean that per person per day the average usage would drop from 150 litres to 75 litres. An article written on behalf on the Good Homes Alliance suggests that the resulting homeowners might no wish to purchase houses that have the perception of lowering living standards, with water saving device and smaller baths. But the Gusto experience shows that with a typical house and a typical family using water quite freely, a rainwater harvesting system can meet very high standards. All this without comprimising on the lifestyle.

Brief history for Freerain and the Gusto Group.

Gusto Construction is an award winning private developer based in the East Midlands of England. Gusto Construction has built various environmentally friendly housing developments, whereby the houses are rated eco-excellent and some of these were built as long ago as 1999, when this standard of build was truely pioneering. With such a small market for environmental building products back then, the supply chain for the technologies was also difficult.

The most difficult was a rainwater harvesting system or a rainwater recycling system as it was known as. Freerain Ltd (formerally known as Gusto Products) was formed to meet the initial requirements of Gusto Construction Ltd. With other areas of the Gusto also forming, the Gusto Group of companies has been operating since around 2003.

Freerain Ltd was also a founder member of the UK rainwater harvesting association, which was formed to tackle the issue of standards and compliance within the industry.

Freerain initially began supplying Gusto Construction for its Millennium Green Development, but the high quality and ease of installation systems soon attracted attention from other developers and self-builders. Freerain quickly established itself as one of the market leaders in the UK.

Following on from several water saving related awards, larger projects began to consider rainwater harvesting. Commercial rainwater harvesting systems come in all shapes and sizes and with that we bespoke the design as necessary.

Types of rainwater harvesting systems

Introduction



The term rainwater harvesting is used to mean the collection of roof water (typically) from a building to provide that building with water to displace mains water. Rainwater in its untreated form can be used instead of mainswater (potable). This means that you can use rainwater (non-potable) in WC's, washing machines and all outside tap functions. Our studies have shown that this accounts for approximately 50% of all water used. So from an environmental perspective, we reduce our mains water consumption by 50%. (subject to the amount collectable from the roof). In commercial projects the amount could be much higher. As the vast majority of water used in an office is for WC's.

Rainwater harvesting systems are have a essentially three main components, these being:

• Storage tanks


• Filters


• Control systems

But there are of course variations on the above.

1. Storage tanks, these can be underground, above ground single peice, above ground sectional. Made from GRP, concrete, plastic or metal.


2. Filters, course leaf and grit, self-cleaning, backwash and inline strainers.


3. Controls can either be direct pump pressure, header tank (gravity) with or without mains top-up. They have a single pump or multiple pumps. These pump can either be submersible (in the tank) or suction pumps (sited with the control panels).
   

In addition to the main components, all items are sometimes added such as ultra-violet sterilisation or monitoring panels as shown above. These add-ons are not required in order for a system to function, but they make the systems more pleasant work with.

When using a rainwater harvesting system it is important to ensure that it complies with the water regulations (WRAS). This is mainly concerned with the cross-contamination of potable and non-potable water and also correct pipe markings inside and outside the building.

Rainwater harvesting Case Study: National Centre for Autism Education

Freerain has recently supplied a rainwater havesting system for installation by Working Environments Ltd (Mechanical & Electrical contractor). The National Centre Centre for Autism Education has been built for the Treehouse Trust.

Source: Treehouse Trust Website, accessed 15 Oct 2008.

Sustainability
The building has been designed to be a low energy and low carbon building. The building is predicted to use 67% less energy than the energy benchmarks set out in the Greater London Authority's guidance for planners. 10% of the energy will be derived from renewable energy sources (ground coupled air pipes).

TreeHouse’s ‘Green Features’ include:

• 
  The roof will be planted with environmentally friendly sedum, creating a habitat for native flora and fauna; softening the visual impact of the building; and providing insulation to reduce the need for additional heating.
• 
  Rooflights on the first floor will ensure maximum daylight levels. Light shafts will provide daylight from the roof down to the ground floor classrooms to minimise the amount of artificial light needed.
• 
  Artificial lighting will be controlled by photocells linked to dimmers to minimise the artificial lighting load.
• 
  Energy efficient boilers will minimise the gas load for heating and hot water. The efficient fabric, form and air tightness of the building means that the heating load is low.
• 
  Rainwater recycling system will supply the WC flushes, reducing energy used in treating and supplying water to the building and treating surface water drained from the building.
• 
  High performance glazing will minimise solar transmission in summer and heat loss in winter, while still maintaining high light transmission to retain daylight levels.
• 
  A ground coupled air system will use the thermal mass of the ground as a heat source in winter (warming the incoming air) and as a heatsink in summer to cool the incoming air. This will result in a carbon saving of 10% or 1056kg/year.

The rainwater system supplied by Freerain included:

• 51,000L underground storage tank (including 27,000L of attenuation volume)
• 4no. Hydro-filters, these are a relatively new type of filter, originally designed for metal reduction from road run-off pollutants.
• Header tank type control system
• Ultra-violet sterilisation system
• Various pumping controls
• LED rainwater monitoring panel

The combination storage tank has allowed the surface water discharge to be controlled, but also cost savings on the total installation.

Rainwater harvesting systems: More popular

Rainwater harvesting systems are becoming more popular in the UK has this for a number of reasons.

1) Water shortages (mainly in the South East)
2) Storm water attenuation
3) Environmental awareness
4) Gadget factor amongst self-builders
5) Government pressure in the schools and hospitals projects.
6) The code for sustainable homes

This last point is very important as we at Freerain are seeing an increase in the number of developers seeking to gain level three accreditation. In terms of water this means a reduction from 150 litres per person per day to 105 litres per person per day. This can be quite hard to achieve particularly during the harder times in the construction industry. It is possible to reduce mains water demand, but using certain conservation messures such as aerate taps, A-rate washing machines and low-dual flush WC's. But in order to meet level three and certainly the higher levels, then rainwater harvesting systems are the way forward. This is because that broadly speaking and assuming that there is enough roof area and rainfall. Then a rainwater harvesting systems can reduce the overall demand of mains water by around 50% or 75 litres per person per day. This means that a design team can be confident that with a rainwater harvesting system there water aspects of the code performance are taken care of.

Freerain has prepared a short introductory guide to explain the rainwater harvesting systems.