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Rainwater harvesting is the collection and storage of rainwater that would otherwise flow down gutters into the drain. Rainwater is collected from the roof, then re-used within the home and garden. This can provide substantial savings on water bills, as well as making your home more sustainable.
Rainwater can be used for all outdoor uses: watering the garden, washing cars, cleaning patios, drives and windows, topping up swimming pools, ornamental ponds and hot tubs. With some plumbing alterations, it can also be used inside the house to flush toilets and feed washing machines. Besides saving on drinking water use, rainwater use encourages less build-up of calcium deposits in appliances. The diversion of rainwater to the storage tank can in many situations attenuate flooding.
The principle uses for rainwater are:
According to the Environment Agency, each person in the UK uses in the region of 150 litres of drinking quality water every day. Around half of this amount need not be drinking water. This means water has gone through an energy and carbon intensive process of filtration, chemical treatment, and pumping from miles away, just to flush down a toilet or water the lawn. This is clearly a waste of our resources. By installing a rainwater harvesting system you will do more than help protect the environment:
Yes! Your garden prefers rainwater to mains water because it does not contain the chemicals needed to make mains water drinking quality.
In recent times many areas have had hosepipe bans, banning the use of hosepipes for watering gardens and cleaning cars. New legislation will give water boards the right to prohibit using hosepipes for other outdoor cleaning purposes such as washing boats, patios, drives, windows, and also for filling swimming pools, ornamental ponds and hot tubs.
With a rainwater harvesting system installed, you will be able to continue using your hosepipe as long as the water is rainwater.
Yes! Typically you will save around 50% on your current metered bill. If you are keen a gardener or have large water requirements, the savings can be even higher. Depending where you are in the country, some annual water bills are now averaging over £600 per year. Some of our customers in the South East of England have reported water bills of over £850 per year.
Absolutely. Domestic rainwater harvesting systems filter the collected rainwater very heavily, and water is stored below ground where it stays at a constant, cool, temperature and away from light. This means it is practically impossible for any bacterial action to occur. Collected Rainwater stays perfectly clean, clear, and odourless in any properly installed and maintained system.
Yes, all water boards have to install a meter at the request of the householder. Installation is free, and some boards provide the meter as well. Some water boards insist on installing a meter with change of ownership, and sometimes, in tenancy of a property.
Rainwater harvesting acts as part of a Sustainable Urban Drainage System (SUDS.) In heavy rainfall the tank fills first, then should the rainfall continue, the tank will overflow into a soak-away. This takes stress off public storm drains.
Water can be boiled and treated with UV filtration to make it drinking quality, yet this typically is only economically viable where occupants are off grid and have no mains water source. Within a normal system, rainwater is classed as non-potable or non-drinking water by UK water regulations. This means it cannot be used for applications where there is human contact (such as drinking, bathing and cooking).
For domestic water use, yes. You should weigh up the arguments for and against digging your tank into the ground:
In favour of digging the tank in:
In favour of situating the tank above ground:
A surprisingly small roof area will give a lot of rainwater: a typical terraced house with a 6 by 8 metres roof area could give 30,000 litres a year depending on the area of the country you live in. Check the tank size calculator and UK rainfall figures shown on that page.
Check the tank size calculator. You can calculate from the size of your roof and average rainfall figures in your area (available on our web site) how much water will come off you roof in a year. The same calculator works out how long the water will last in a drought from a) your garden size, b) how much water you want to give to your plants, and c) the size of your tank. Aim for between 1 and 4 weeks drought protection and a tank size which also suits your budget.
The filter installed in the pipe to the tank is essential for larger tanks where water may be stored for a longer time. It will help prevent water becoming smelly and discoloured by removing leaves and other debris. This also reduces the sludge accumulating at the bottom of the tanks, and reduces clogging of tap outlets, hoses and watering-can heads. High quality filters (such as in the turret of the tank) separate debris out and flush it down the drain or soakaway. Some downpipe filters eject debris straight out the side, while cleaned water goes into the tank. Both kinds are easy to maintain.
For even cleaner water, an overflow siphon collects smaller particles such as pollen which can accumulate after filtering on the top layer of rainwater. The integrated u-bend stops vermin getting into the tank through the overflow outlet. Where the rainwater flows into the bottom of the tank, a calming device prevents the flow from stirring up any silt on the bottom. A floating intake to the pump takes water from the cleanest place, a few centimetres below the surface. A pump maintains a good pressure and flow of water round the house and garden. Pumps (such as the Forta Duo and similar pressure-sensitive pumps) turn on automatically when you turn on a tap or flush a toilet. It stops on its own as well. Other less expensive pumps will only stop when the water level in the tank is too low for it to work any longer. Although some pumps do have their own filters, they perform much better if the rainwater has been filtered already by an exterior filter.
A filter installed in the down-pipe to the tank, or in the top of the tank itself, is a good addition for all tanks but is particularly to be recommended for larger tanks installed above ground where water may be stored for a longer time. It will help prevent water becoming smelly by removing leaves and other debris. This also stops sludge accumulating at the bottom of the tanks, and tap outlets, hoses and water-can heads clogging up. Some filters separate debris out and send it on down the drainpipe. Other filters eject debris straight out the side, while cleaned water goes into the tank. Both kinds are easy to maintain. A pump makes distribution from the tank easier by maintaining a good pressure. Quality pumps (such as our Forta Duo pump) with a pressure-sensitive switch turn themselves off when water flow is not needed; when using a spray-head, you do not have to run in to turn pump off: it will stop when you click the spray-head to off. Other less expensive pumps will only stop when the water level in the tank is too low for it to work any longer.
Pumps which switch off when no water is being drawn (such as our Forta Duo pump) and which can be used both in and out of the tank are the best. These allow you, for example, flexible watering. When using a spray-head, you do not have to run in to turn pump off: it will stop when you click the spray-head to off. Other less expensive pumps will only stop when the water level in the tank is too low for it to work any longer. If you order a system with a rain management system which turns the power on and off to the pump (such as some versions of the Rain Director) then the 800W StrongArm is our choice.
a) Butts and tanks 1000 litres or less, do-it-yourself systems:
It is tempting to use a small diameter pipe (hosepipe or 25mm (one inch) diameter from the collector-filter to the tank. However it is worth the effort to use 32mm pipe to the tank. A narrow pipe will collect the bulk of water from light rain and drizzle, but during the critical period of collection, i.e. the summer, you need to be able to catch the available water which typically falls in sudden storms at that time of year. So give yourself a chance by fitting the biggest pipe possible. In our experience, 32mm is the best. Try to buy usually Spiroflex or a similar pipe which keeps its shape (transparent tubing from a DIY shop twists and caves in, restricting water flow, so avoid it). You can get Spiroflex from any aquatic or fish pond supplier, often in the back of your garden centre, or order it from us. The connection kits are available separately on request.
b) Tanks larger than 1000 litres and all underground tanks, professional systems:
Rigid drain-pipe is recommended, in either of the two 75mm or 100mm diameter standard sizes, so that the flow is unrestricted and so that the weight of earth or backfill does not collapse the pipe. Installations of this sort would normally be installed by your contractor or plumber. In both cases, make the pipe from the tank to the appliances or garden taps as wide as practical, certainly not less than one inch (25mm) diameter. 32mm is preferable to maintain a good flow rate and pressure for garden sprinkling. Use MDPE pipe with push fittings; use black pipe not blue to indicate that the rainwater is non-potable under the UK Building Regulations. Ensure that the output pipe from a submerged pump is flexible enough to allow the user to draw the pump out of the tank (using the cord) for filter cleaning.
A filter is recommended in every Rain Water Harvesting installation and essential if the rainwater is going to be used in the house. It is most critical when leaves often fall on the roof being used, such as a low roof with trees nearby.
Rainwater Harvesting Ltd sells three types of filter.
1) The down-pipe filter/collector takes the water feed for your tank through an outlet in the side; the leaves or other debris continue down the existing down-pipe from your gutter. Use this next to the house when adapting an existing down-pipe. When the tank is full, excess water flows on down the down-pipe.
2) The leaf extractor filter (e.g. Rainus filter) pushes leaves or other debris out of the side of the filter and the clean water continues down the down-pipe. Use this type on out-houses, garden garages, stables etc when the down-pipe goes straight into your harvesting tank and when you don't mind leaves being pushed out the side.
3) Underground tank kits come with a professional self-washing filter, like the Optimax Pro, fitted in the turret of the tank. Leaves are pushed by the water flow out into the waste pipe.
Both down–pipe filters and leaf extractors have overflow capacities as big as the original down-pipe to which they were fitted. You might get back up of water and overflow at the level of the gutter, but only in such extreme rain fall that you would probably have had gutter overflow anyway.
The siphon skims small particles of dirt off the top of the water by creating a more rapid water flow from time to time. This is rather like the flush of a toilet but on a smaller scale. It keeps the water in the tank cleaner than a plain overflow pipe.
Yes. You can have a small water butt (say 200 litres) collecting rainwater off the house down-pipe. As it fills, an automatic level-sensitive pump sends the water through an above-ground or buried hose-pipe or 1 inch pipe to a much bigger storage tank underground or elsewhere on your property. You should plan for a soak away to handle excess water at the storage tank.
Yes, but you'll empty the tank rather quickly. A normal movable sprinkler can use 1,000 litres per hour, so a 200 litre tank would be empty in 12 minutes! We recommend the use of a drip feed system (such as those from Gardena and Kar) where water is directed to the roots of the plants at night, controlled by a time switch. The lawn should be watered with mini sprinklers for a few minutes daily if required, i.e. consider fitting a soil humidity gauge.
No, if you are going to use a pump. And even without, attach a short length of pipe to the tap and water will flow into a watering can or bucket until the level of the water in the butt is lower than the level you want in the can.
In a word, no. We have been surprised at how lacking in diligence most of the manufacturers have been in this respect. Here at RainWaterHarvesting.co.uk we make every effort to inform buyers what they're getting and we'll source and provide any extra bits needed. If you buy hose, try to use 32mm spiral reinforced (25 or 32mm black MDPE for domestic supply). Flow is better and connectors easy to get.
Yes but with a suitable pump. Most pressure cleaners, like the Karcher, need a certain amount of pressure and flow rate of the water at arrival. We have found that the small pumps in the £30-£50 range do not deliver enough pressure, but better ones like the Forta Duo work fine. Look for 500 to 1100 watts in power and 3 to 5 bar pressure. Such cleaners use a lot of water so check the tank level before use (normally by lifting the cover and looking).
Yes. Use an underground rainwater harvesting tank, pump and filters to ensure that the water being fed to a swimming pool is well cleaned. The Building Regulations are interpreted differently by different council inspectors: generally it is understood that rain falls into a swimming pool anyway, so using rainwater properly filtered provides an even better quality of water. Fish such as Koi Carp much prefer the untreated, un-chlorinated rainwater and less chemicals may be needed.
You can download the tank size calculator from this web site at or email us the details and we'll do it for you. We would need to know the roof area of the building, its location in the UK, how many people in the house, how many toilets and washing machines and whether the water will also be used in the garden.
The Code for Sustainable Homes now puts pressure on builders to install rainwater harvesting in new-builds. A rating against the Code for Sustainable Homes, which measures nine categories of sustainable design including energy, water and waste, will be required for all new homes. Homes which exceed the sustainable standards in existing Building Regulations will be awarded up to six stars. Those homes that have not been assessed against the Code will score a nil-rating. Many councils are now giving planning permission only if the development scores between 3 and 5 against the Code. If you would like to get a Sustainability Code assessment please register here and include in the notes section "Sustainability Code assessment please.
No. A properly installed and maintained system will provide clean, colourless and odourless water. As the rainwater is heavily filtered and stays at a constant, cool temperature with no light exposure there is practically no chance of any bacterial action. Visually, there is no way to distinguish between the harvested rainwater and mains water.
No, we do not recommend using water off the hard standing or patio because oil spills or other waste could enter the water destined for washing clothes and flushing toilets. There is also typically far more dirt accumulated from ground water than rainwater from a roof, clogging filters.
RainWaterHarvesting.co.uk supplies all the equipment for domestic rainwater use. Select one of the kits which include the tank, filter, pump and accessories needed for such systems. Use of rainwater in the house requires you to plumb pipes to feed rainwater to the toilets, washing machine and one or more garden taps. The UK Building Regulations classify rainwater as non-potable so use in showers, baths and in the kitchen is not permitted in the U.K. - even though people in many countries of the world use stored rainwater for drinking. Do please check with local authorities about any other regulations that might apply.
This depends on five factors;
The tank size calculator on this website will help you work out your needs and we will check your calculations for you on request. It may be worth remembering we often specify the tank size on the size of the home. So if there are just 2 of you in a 5 bedroom property we tend to specify a tank that will be large enough to cater for extra people should you ever move out. Working out how much water you're likely to use in the garden can be tricky. The best way is to assume if you're using a hosepipe or sprinkler you will use around 1000L/hour then try and work out how many hours of watering you do in a week. As a general rule the following applications would be typical for domestic use;
The automatic mains backup switches in, so you can go on flushing toilets and washing clothes without interruption. But you would not be allowed to water the garden when there is a hosepipe ban if the mains water is flowing.
Remember to specify one of the three mains water backup options;
Nominal working power consumption is 550w with a surge in power consumption each time the pump starts. The Rain Director uses about one eighth of the power because it lets the header tank empty by gravity before filling it again.
74 decibel unshielded or 70 decibel shielded. A dull hum. The Rain Director, on the other hand, makes no noise in the home because the pump stays submerged in the underground tank.
Yes but... Grey water is waste water from the house (from basins, showers, baths, washing machine and dish washer) but not toilet wastes and food wastes derived from garbage grinders (called "black water"). It's mostly a question of personal taste whether to use grey water to water the garden, but if you are not a heavy detergent user, then, yes. Grey water should not be used to fill swimming pools and it might give a smeared finish when washing cars. You should consider a specialist treatment plant (http://www.greywater.com) and you should also check any applicable regulations. We do not recommend putting grey water in your rainwater tank. If you have a big roof and plenty of rain you might choose not to bother with collecting grey water.
Rainwater is better than grey water as rainwater contains less detergents, soaps, chemicals and bodily dirt. But in times of severe water shortage you should try to store grey water for garden use.
No. Legionella cannot grow without light exposure or in temperatures below 20°C. An underground rainwater harvesting tank is completely dark and water stays at a constant temperature around 4°C all year.
Rainwater tanks come in all shapes and sizes. However over the past years the "shallow dig" F-Line range has become increasingly popular for the domestic market.
The F-line flat tank can be installed into much higher water tables than a standard round tank. If you don't know what your water table will be like in the winter, you're safer to install a flat tank. The F-Line tanks are flatter and vary between 1m and 1.5m in depth. The excavation can be up to 70% less, meaning little earth excavation, easy handling and less cost for you! The small excavation pit is easily filled in and your garden will look just like it did before.
a) the low ambient temperature underground in summer prevents the water getting brackish and discoloured. For this reason it is not suitable to provide rainwater in the house from an overground tank.
b) the tanks are big and ugly... not what you want in the garden from an aesthetic point of view.
The best way to purchase rainwater harvesting equipment is in kit form, i.e. with all the parts supplied to make a complete system. Our domestic water kits include not only the pump and filters but also one of the three types of mains backup;
Your contractor needs to supply the piping to connect:
The client is responsible for complying with applicable regulations which can be interpreted differently in parts of the country. Most building regs for domestic use of rainwater require that a device must be fitted which prevents backpumping of rainwater into the mains system such as a tundish at the outlet of the mains to the tank.
The tank should be located convenient to a point where the downpipes from all four sides of the building can be brought together in one 110 mm drain pipe. This is usually the lowest point in the grounds if there is any slope. The pump will then draw water from the tank up to any point in the building. It should join the internal rainwater piping network in a utility room or the point where the mains water arrives in the building.
We would not recommend using water off the hard standing or patio because oil spills or other waste could enter the water destined for washing clothes and flushing toilets. Some clients use a separate tank for run-off (and grey water) and this water is used on the garden only.
Yes, use a dirty water pump with float switch from our range. Make a culvert or manhole at a low point in the garden into which surface water will flow. The pump starts automatically when water is present; you can route the outlet pipe up to a drain or soakaway.
It is vital that the rainwater flows smartly over the filter in the turret of the underground tank so that leaves and debris are flushed away. If the top of the tank is lower than the drain then you need one of two solutions.
Ensure that the pump has been installed with its cord (supplied with most pumps) attached both to the pump and to a point at the top of the tank. Ensure also that the output pipe from the pump is flexible enough for you to be able to pull it out of the tank. If the pump is fitted with a basket filter, clean it out. There are no other serviceable parts
Yes, the pump is capable of delivering output necessary to power a high pressure sprinkler. You may though, empty the tank quickly unless it has been appropriately specified for your needs. A high pressure rotating sprinkler can use 1,000 litres per hour, so even a large, underground, 3000 litre tank would be empty in 180 minutes of continuous use! Programmable irrigation systems are recommended, in order to prevent over watering.
If you are watering flower beds and individual plants, then a leaking or soaker hose is the most water efficient. The water goes straight into the ground where it is needed. A typical leaking pipe uses 1 to 10 litres per metre per hour depending on whether it is 4mm or 12.5 mm diameter. Drippers (trickle feed) are water efficient also, directing water exactly to where water is needed. Fixed rate drippers use 4 litres an hour per dripper.
Mini-sprinklers can be directed to specific areas and plants typically vary in range from 1.5 m, 2m and 3m, and use on average 55 litres per sprinkler per hour. For example, a 40 sprinkler kit covering 750 m2 would use @ 2200 litres an hour. A typical spray sprinkler covering 240 m2 may not cost very much (eg £12.99) but is not water efficient, using @ 1000 litres an hour. To water 750 m2 would therefore use @ 3000 litres an hour, nearly a third more than the mini-sprinkler system.
The Royal Horticultural Society says that "up to 24 litres per square metre every 7-10 days will be sufficient to maintain plant growth" (ie 2.4 litres a day) or "2.5 cms of water per plant every 10 days during dry spells". For example, running a sprinkler system for 2 or 3 minutes every 24 hours should be enough during a dry spell. This is only a guideline as the water need will vary with the size of the plant.
In principle yes, but we recommend that the hose off the pump is a one inch (25mm) or larger pipe as far as a connector or stand pipe tap. This is because water flowing in the constriction of a half inch hose means that you do not get sufficient pressure and flow rate at the far end.
The filters used in domestic systems are self cleaning. Situated inside the tank, the filter removes any leaves or debris from the roof, allowing the clean water to enter the underground tank. The debris remaining is flushed into the overflow, and is discarded into the soak-away once the tank eventually does overflow in a heavy rainfall period. Due to its self cleaning function, typically the filter will only require one visual check per year.
A small amount, yes. Most tanks accumulate a millimetre or two a year, but there are 3 further devices in our kits which ensure clean rainwater in the home.
The tank manufacturers mostly say you should inspect the tank for silt build-up every couple of years, but it can be much longer before any intervention is required. To get the silt out, lower a "dirty water" pump to the bottom of the tank when it's nearly empty and pump out the silt with the remaining water. A hose or pressure washer could also be useful.
See our section on guarantees and service.
The pumps in the £200 range are strong and long-lasting. They require no maintenance and, being submersible, there are no user-serviceable parts. In the case of breakdown the pump can be pulled out with its cord (the top of which is attached to the inside of the tank turret at installation) and replaced. Check with your supplier about the guarantee involved.
Yes. It seems un-necessary for the pump to start off pumping every time a toilet is flushed, especially because a disproportionately high amount of electricity is used when the pump starts, and because the pump, in simple installations, goes on pumping for some time after it stops supplying water. The Rain Director solves these problems. Its microprocessor-controlled roofspace header tank uses about 8 times less electricity, wears the pump less, provides water during a power cut, and has auto flush and holiday modes.
No, even though the filters clean the water heavily, a small amount of very fine silt still gets through. Most tanks accumulate a millimetre or two a year, but there are 3 further devices in our kits which ensure clean rainwater in the home.
The UK Building Regulations specify rainwater as non-potable water. But if you get the water tested and fit the right equipment you can use your rainwater all over the house even for drinking.
The UK Government's requirements are at http://www.opsi.gov.uk/SI/si2000/20 003184.htm. It's quite a read.
The WHO's recommendations are at http://www.who.int/water_sanitation _health/dwq/gdwq3rev/en/index.html
In practice, it is vital to get water tested if the users or authorities want to be certain of its quality. There are testing companies all over Britain and one can identify them locally when required. Most council inspectors will want to see test results and a confirmation from a supplier that the equipment will handle whatever might be polluting the water.
The most common pollutants and their remedies are as follows:
We know of nobody who extensively recommends the installation of equipment for adding chemicals to rainwater, but it's an option.
The bulk of tests in the UK show the presence of minute quantities of bacteria (as would spring or well water) for which Ultra-Violet filtration is ideal. Our recommendation is to install the Carat tank with a UV filter, then have a test done after commissioning and the first couple of rains. The most popular UV filter from Rainwater Harvesting Ltd for use in the home are the Silverline UV-DS15 and UV-DS30 delivering 8 and 21 litres of clean water per minute for between 2 and 3 hundred pounds.
Our F-Line tanks are guaranteed for 25 years. All other products are (such as pumps and management systems) are guaranteed for 2 years.
Yes! We have a professional, full time technical support team. Extensive telephone support is provided to assist installations and technical issues.
Yes, this can either be built into the price if you require a commissioning visit, or can be arranged upon request.
As we hold everything ex stock, in our 65,000 sq ft warehouse, we normally supply systems within 3-5 working days.
No, we design, develop and manufacture many products such as our award winning Rain Director and Backup in a Box management systems. Our sister company Hydroforce Pumps Ltd manufactures the submersible pump used in most systems.
You can find more information about why you should harvest rainwater and Planning & Incentives.