Save your money…save your water…save your environment!
The rapid expansion in companies who supply rainwater harvesting of varying quality has resulted in the publication by British standards BSI-code of practice BS8515:2009. This guide has been produced to assist architects, construction companies and contractors to comply with the new standard in the same way that all systems from combined harvesters do.
Welcome from the combined Harvesters team
Formed early in 2006, Combined Harvesters have grown to become one of the foremost suppliers and fitters of all types of rainwater harvesting systems from simple water butts to full underground storage systems and all associated integral parts.
We, unlike a great many companies, are not affiliated with one supplier but source our products based on market trends and the specific needs of our clients.
With such a comprehensive range of products on offer, we believe our service to be second to none in the industry and one which we continually strive to improve.
Our business history is not quite so young as Combined Harvesters however, we have been in landscape construction and design for 25 years in both the domestic and commercial sectors which has given the team great knowledge and experience to bring to this blossoming sector.
When you deal with us, you are not only getting fast, friendly advice from a family owned and run company but you will get the benefit of our integrity and business skills to give you the most comprehensive system, specifically tailored to your needs within your budget.
Below are a few frequently asked questions to assist with the guide BS8515
What is Rainwater Harvesting?
Rainwater harvesting is a way of saving the rainwater which would normally flow off a roof and down the drain, and using it as piped water to flush toilets and for the garden watering, yard washdown, vehicle and car washing, and even for your washing machine, instead of using expensive treated drinking (potable) water.
Are there planning regulations associated with rainwater Harvesting?
They are not required directly by Building Regulations, although they may be linked with the Planning Permission for the storm-water management of the site. Building Regulations do cover the installation itself, tank siting & pipe runs etc.
Will a system affect my homes eco rating?
Yes, rainwater harvesting is an important ER criterion. The EcoHomes rating system addresses all aspects of reducing potable water demand in a dwelling. Installing a rainwater harvesting system adds to the credit rating for water use.
What types of rainwater harvesting systems are there?
Un pressurised: rainwater is gravity fed from a header tank, usually in the loft to the point of use.
Pressurised: The rainwater is pumped directly from the above or under-ground tank to the required point of supply. i.e. toilet, outside tap etc.
Is there a danger of legionella?
No, the system does not provide the conditions necessary for the cultivation of Legionella. With the water stored underground it is dark cool and is kept well oxygenated. Legionella cannot cultivate in these conditions.
How is the system maintained?
Filters should be thoroughly cleaned once a year and we recommend a full 'flushing' of the system every three years. A treatment with an anti-algicide such as sprayguard is also recommended. A correctly designed harvesting system overflows on a regular basis to remove floating matter and the pumps are very reliable. Maintenance should only be carried out by qualified or experiences personnel. Combined harvesters have their own teams available year round to keep systems working efficiently.
What kind of pumps are used in the systems?
Pumps can be housed either internally in the tank or mounted within a control unit fitted in a garage, plant room etc. Pumps should have run dry protection and should have a pressure switch fitted to stop hunting. Internal tank pumps need to be constantly submersed in water to prevent damage from the air, from debris or sediment that may be sucked in. An external pump or control unit should have an audible alarm to identify faults in the system, when fresh water is being used etc.
How much does it cost to run a rainwater harvesting pump?
It typically takes 1.5- 2.0 kWh to pump 1 cubic meter of water (1000 litres). For a typical house using rainwater for WCs, washing machine and the garden, pumping costs are between 5-10p per week
Do I need to have a water meter?
This is not generally necessary; however the absence of one will reduce you seeing the benefits of harvesting rainwater immediately.
What does the British Standard BS8515:2009 cover?
BS8515 covers the design, installation, water quality, risk management and maintenance of rainwater harvesting systems. This applies to both new and retrofit properties.
What is the payback period?
This figure will depend upon the rainwater that you collect and the use. A typical domestic client will see a payback between 5-10 years. Commercial clients can reduce this figure to 2-5 years.
Is it only for new builds?
No systems can easily be retro-fitted.
What design aspects are to be considered to comply with BS8515?
Designs should be provided by an industry expert, amount and intensity of rainfall, type of intended applications both now and in the future will be considered. Tank size will depend upon ground conditions and surface water. All these as well as filtration requirements, end use by clients, site restrictions and other factors not necessarily covered by BS8515 will be considered when designing a system.
What happens when there is no rain?
In the absence of no rain, correctly designed systems will have a 'mains top up' facility. This will fill the tank with the minimum required amount of water to keep it functioning until the rain returns..
Is rainwater harvesting suitable for work as well as at home?
Yes, in schools, hospitals, offices, commercial premises, rainwater can typically be used for toilets, vehicle washing, yard wash down and watering plant pots/gardens.
Can it be used when there is a hosepipe ban?
It is possible to use a hosepipe connected to a rainwater tank, provided that the tank is not connected to a mains water supply. Many people are doing this already by using a water butt.
Is it only for houses?
No, bungalows and commercial premises are also very suitable, the only limitation is the area of the roof to capture rain, in fact commercial and industrial buildings can make the largest savings.
Where is it installed?
The tank should be buried under a car or vehicle park, landscaped area, garden, patio or drive, with space left for the round access cover. Most systems are designed so that they can accept cars driving over them if suitably installed. Or an above ground system can be installed next to the house or property.
Are there any grants available?
Not for domestic installations yet, although several organisations are petitioning the government for assistance. For commercial installations, there is a tax relief scheme (ECA) for suitable approved equipment on the Water Technology List.
How clean is the water?
The rainwater is filtered as it enters the storage tank, to remove particles and other matter. It is kept in the dark and kept oxygenated to discourage algal growth, and properly designed systems are designed with calming inlets, which ensure that any sediment at the bottom of the tank does not get stirred up. The water is not drinking water fit for humans.
How do you stop debris from entering the system?
A filter is fitted along with a ‘calming inlet’. The filter has to meet strict criteria covering its weather resistancy, accessibility and efficiency.
How much rainwater does a system collect?
This depends on the area and angle of your roof, and your rainfall. Averages of 100,000 litres per household are commonly quoted, much more for large roofed commercial buildings.
Is the tank covered by BS8515:2009?
Yes, all tanks are covered. They need to be water tight, discourage microbial growth, avoid stagnation and thereby legionella .Tanks need to be suitably load bearing and need to resist floatation.
Pipes to and from the tank need to be clearly marked, rainwater pipes can be green or black (not blue) .Special marker tape can be purchased to show piping on a scan.
Does the tank need an overflow?
Yes, the overflow needs to be the same diameter or even larger than the inlet, it must also be fitted with back flow prevention. Overflows are important as a tank should be the correct size so as to overflow at least twice a year to ‘flush the system’.
How much would this save on water bills?
Depending on your normal usage, it can save 30 to 50% for the domestic user and 80% for the commercial user of the treated drinking water from the mains. Having metered water is the best way of appreciating the difference.
So, why should people buy Rainwater Harvesting systems?
To save on water bills and show they use water, an increasingly precious resource, responsibly to make a difference to our environment.
How does rainwater harvesting work?
A storage tank is fitted to your storm water drain from your roof, and falling rain enters the tank through a filter which removes leaves and other matter. The storage tank is usually buried under car or vehicle parks, a garden or under the entrance access or drive, and contains a pump which pumps the rainwater to the building where it is piped to the toilets, and to the outside taps. Above ground tanks are also available.
How much water can a system save?
Depending on your normal usage, it can save 30 to 50% of the treated drinking water from the mains in houses and up to and up to 80% of the treated drinking water in a business or commercial building.
What can you use the water for?
Filtered, untreated rainwater should only be used for non- drinking or bathing purposes: toilet flushing, gardens and vehicle or yard wash downs.
How much does it cost?
Domestic systems can cost from about £2500 up to £4000 plus including installation costs, depending on size of tank. Commercial systems can cost a lot more depending on size and requirement, but usually have a much quicker 'pay back' period due to the size of roof and high usage.
Could rainwater get into my drinking supply?
Not in a properly designed system, the pipe work is entirely separate and should be identified as non-potable. BS8515:2009 stipulates that backflow prevention should be fitted upstream of or at a point where any two systems meet. This form of back flow prevention must be of type AA or AB Air gap conforming to BS13076 and BS EN13077.
Do I need a big roof area to make it worthwhile?
No, most domestic roofs are more than adequate, but the bigger and flatter the roof area, the more rain will be captured, and the more the rainwater will substitute for treated mains water.
Is Rainwater Harvesting a new idea?
No, collection re-use of rainwater from roofs can be traced back thousands of years in hot, dry countries around the Mediterranean. In continental Europe, some 100,000 are installed annually; Germany has been using and refining the technology since the early 80s.
Can a roof affect the efficiency of a system?
Yes, all these need to be free-draining and suitable to stop debris from entering the system. Other roofs such as green roofs etc absorb water and results in less run off and more colouration.
This guide has been produced to assist professionals who are interested in the specifications of rainwater harvesting systems. Enabling them to make an informed choice of supplier based on the criteria set down in BS8515:2009. At Combined Harvesters Ltd we are committed to a long term approach to the supply of all rainwater harvesting and stormwater management products, ensuring quality throughout the chain.
Save your water…save your money…save your environment.
If this water is put to use washing the car, watering the plants, washing the windows and even flushing the toilets , imagine the savings on water rates and the benefits to the environment. There are many methods of rainwater harvesting , barrels fitted to a downspout from a roof come in many shapes and sizes , some practical and some aesthetic. Thought should be given to sturdiness , child friendliness and safety, a cheap system will crack when the frosts come and would be a waste. Also run off of excess should be considered. Underground tanks can store anything from 1000 litres to as much as 10,000. Although a common size would be 2800 litres. A special pump will deliver the water to a hose pipe on demand or to a header tank in the loft. A flotation valve automatically shuts off the pump if the tank is emptied. A soakaway system will remove excess water when full naturally into the water table. Apart from the above benefits there are others , less obvious-:
German households use rainharvesting systems up to 300 % more than households in the United Kingdom. However the use of these systems have increased by over 300 % in the last two years here.
Your typical rainharvesting system can yield up to 50 % of your water needs, a typical period for payback on a family with a high water demand is three years.
An average 4 bedroom family home roof can capture up to 100,000 litres of water each year, whereas a typical family's consumption for standard use such as toilet flushing, garden watering , washing etc is 70,000 litres
Rainwater harvesting systems are made up of the rainwater storage tank or rain harvesting storage vessel of some sort, along side the rainwater harvesting system filter and the rainwater harvesting pump or rain harvesting delivery method. Rain harvesting products come from a wide variety of specialist rainwater harvesting system manufacturers. Combined harvesters specialise in both commercial and domestic harvesting of rainwater.
In commercial rainwater harvesting systems the rainwater is stored in a larger GRP rain storage tank, the rain pump delivers the harvested rainwater to the required source. Rainwater harvesting information can be usually sourced from company brochures.
Rain water collection can be in standard rain water collection tank(s) made from GRP or from HDPE. It is important that the rain water collection tank has smooth sides to inhibit algae growth. Most rainwater harvesting companies have ‘how to harvest rainwater’ training classes. The water storage or water storage tank underground or above ground water storage tank is usually for non potable water storage. Rain water is collected from the rainwater gutter and the fallen rainwater is filtered through a rainwater downpipe. Some rainwater filters are actually fitted to the rainwater downpipe and the filtered rainwater is collected in a plastic tank or water butt which is housed nearby.
Some water butts are injection moulded and other water butts are blow moulded .This generally means that the water butt can be a lot lighter than standard water storage tanks .Some waterbutts have downpipe fitted diverters and filters. Other water butts have separate filter diverters . Underground rainwater storage tank, also known as underground storage tanks hold the rainwater, but you should be mindful not to have an oversized rainwater harvesting tank as the rainwater stored has the potential to go off and smell.
Combined harvesters ltd fit commercial rain harvesting systems and commercial rainwater harvesting filters.
Suppliers are Graf, Kingspan, Titan, Polypipe and Raincatcher.
Water tanks and water butts come in all shapes and sizes to suit individual needs and requirements.
Our Geotextile membrane department pride ourselves in the ability to supply all woven geotextile membrane along with standard non-woven geotextiles and geomembranes. These geotextile membrane fabrics come in many weights. Clients should be aware that a consideration for geotextile membranes porosity should be made. Terram geotextile membrane and geomembrane is a generic brand as is greenseal, firestone pond liner, epdm liner and epdm pond liner epdm liner is imported and also goes by the name of bitumen membrane, butyl box liner, butyl liner, butyl rubber, butyl pond liner and others.
Woven geotextile such as 609 is the ministry of transport rating and is used for horse manages, horse ménages as a stabilisation fabric before the geomembrane of heat treated fleece membrane is put in place. The non woven geotextile membrane such as terram 1000 or bona rtf membrane is the stabilisation upper layer that allows water to percolate through. Not a weed fabric or weed prevention membrane but a superior non woven geotextile membrane. A geomembrane comes from other suppliers such as rhino or gtex or geotex and has the ability to perform in similar manners. Geomembranes are seam welded to stop seepage in attenuation trenches or infiltration trenches. Porous welded geotextiles will be classed as protective membranes around the infiltration or attenuation trench when designing a system for sur2 regulations bs8515:2009. Weedex and weed prevention fabrics are generally considered to be hydrophilic or fully porous fabrics. Woven membranes are less able to allow water to permeate through and some woven heat treated geotextile membranes allow very little water to permeate through the fleece membrane fabric. Terram membranes are the industry recognised standard for all types of woven geotextile, woven geomembrane, non woven geotextile and geotex, terram 1000 being the most popular.
Our recessed manhole cover and drain cover department sell concrete manholes, iron manhole covers, precast concrete manholes, drainage covers, gullies and gully traps, inspection chambers and inspection covers, grass top recessed covers, internal recessed cover along with a full range of commercial covers. We have a wide range of square and round manhole covers, frames, recessed trays, block pavior trays, and gratings.
Recessed man hole covers, sometime referred to as recess tray cover or drain covers are used to mask the presence of man holes and inspection chambers in paved areas.
Manholes usually consist of 3 parts, the manhole frame, the tray, and the manhole cover.
We pride ourselves with the ability to cover the earth with manholes so that they are blended in with the world and go unnoticed in everyday life.
Does your man hole cover in your garden look awful? Do you wonder what you neighbours think of the manhole lid? Would you like to conceal your man hole in your garden so it looks more natural? Well, at recessed manhole covers we can cover your manhole and make if go unnoticed in your garden. That’s what we are specialist at. We also sell drainage covers and gully traps as well as recessed concrete, iron and precast concrete manhole covers.
We have the solution for your man hole and drainage problems here at recessed man hole cover. Its not only manhole covering problems we solve, we also have storm water drainage solutions, including gully and gully traps.
Inspection chambers and covers are for inspecting inside the manhole. They are needed to gain access into the manhole so if you need to get inside, please buy an inspection cover for this. We have square and round covers
We supply Clark drain, Aquaknight, Chambermate and Peter savage manhole products. Channel drains and debris traps.
All our manhole covers, channel drains, and gully traps all comply with the BS EN 124:1994 standards.
A soakaway or soakaways drainage design is important for many reasons including; flood, flood defence, flood prevention, stormwater management, sustainable building, sustainable drainage, sustainable construction, Sustainable urban development, Urban hydrology, Wastewater management etc.
Sustainable construction, sustainable design and sustainable housing are in the forefront of everyone’s minds at the moment and is an important thing to consider when building or renovating any house or garden. Creating a more sustainable, eco friendly house will add to the selling potential.
Flood defence, flood prevention and storm water management are certainly a paramount with the extreme flooding we are experiencing at the moment. The design of your rainwater drainage and land drainage is important, to create good flood prevention measures. A good flood prevention measure is a soakaway for rainwater and surface water run off. Construction of a drainage soakaway will require the digging of a drainage ditch. Digging this drainage ditch is not difficult and it the first step after the drainage design for waste water management has been decided. Drainage design will include a range of drainage products, drainage pipes, drainage crates and geotextile membrane being placed in the drainage ditch. You may also require a drainage sump. The drainage design may include permeable paving or rainwater drainage from the driveway.
Stormwater management systems come in all shapes and sizes, they can be made to measure or buy as a complete pallet package. Soakaways are an easy stormwater management and prevention solution and a fantastic way of flood defence and waste water management, helping immeasurably towards the creation of sustainable living and sustainable design.
Construction of driveway drainage or permeable paving may be helped by a local landscape gardener, who may also assist in digging any drainage ditches or drainage sumps and may be able to offer further advise on rainwater drainage, sewer design and Urban stormwater management. Combined harvesters can also offer the services of our own in house team for such things as drainage construction, installation for a soakaway or drainage solution, digging any drainage ditches and drainage sumps and the laying of permeable paving and driveway drainage.
Soakaway flood prevention measures for subsurface drainage, in summary, are an easy drainage design evolving only a small number of drainage products and little constructions design knowledge. Combined harvesters supply a full range of drainage pipes and drainage products, including permeable paving for driveway drainage. We also can provide advise and assistance second to none during and after the drainage design and construction of your stormwater management solution.
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