Rainwater Harvesting: Installation advice for installers

Rainwater Harvesting: Installation advise for installers

Adrian Gatford, National Sales Manager at Kingspan Water, answers the ten most common questions asked when researching the installation of rainwater harvesting systems.
1. How are rainwater harvesting systems installed?
Installing a rainwater harvesting system is relatively simple, but it requires various skilled trades at different stages of a build.
Initially, the builder or civil contractor excavates a hole for the system’s underground tank and its requisite pipework, backfilling as necessary.
It’s then the turn of the plumber to connect the internal plumbing and, for gravity systems, connect the tank to a header tank. An electrician connects the wiring of the control panel and the pump before the system is finally commissioned.
As long as manufacturer guidelines and regulations are adhered to, there should not be issues with any part of the installation, commissioning, or safe working of a system.
2. How do you actually design a rainwater harvesting system for a house or development?
We always recommend bringing in the company supplying the system at the beginning of the project planning to allow them to create a specified, pre-designed system that includes sizing the system and storage tank in accordance with the British Standard for rainwater harvesting, BS 8515, and The Code.
The geographical location, annual rainfall, the area and type of roof or collection surface, and intended applications (now and in the future) are all considerations to ensure full compliance with BS 8515. The Standard also describes how it is possible to use an oversized rainwater harvesting tank for flood water attenuation, to lessen the chances of flooding.
3. Should the tank be placed under hard-standing or in the garden?
It is more cost-effective and practical to site the tank in a garden, to the front or rear of the building, rather than under a driveway.
Siting the tank in a driveway, for example, can add cost to the project and the tank would also require a heavy-duty access frame and cover as well as a concrete slab over the tank to protect it from the vehicle loading.
4. Should the builder use gravel or concrete to back-fill the tank?
Some manufacturers advise using peagravel to back-fill a tank in dry site conditions.  However, a system which has been installed to reduce surface water run-off is likely to be sited on impervious soil. If the tank is surrounded by peagravel, surface water can filter down and collect around the tank creating a buoyancy issue. The problem can be avoided by using a concrete backfill under these types of conditions.
It’s also worth bearing in mind that, during back-filling, dirt can get into the tank, so we suggest covering the neck to prevent this happening.
5. What about Water Regulations?
Installing rainwater harvesting equipment brings with it new levels of Water Regulations requirements which are vital to protect the public water supply.
Many of the regulations revolve around three principle requirements for rainwater harvesting equipment to comply with.
Marking and colour coding of the plumbing is a requirement to ensure that pipes carrying rainwater are not accidentally connected into at a later date to satisfy potable water requirements.
Rainwater harvesting pipes are black with green stripes – which are now available through merchants – while potable water pipes are blue. The pipework must also be labelled every 500 metres internally and a Type AA or AB air gap in the system is required to avoid any contamination of mains water supplies.
6. Do we need to let the Water Authority know?
If a system incorporates a back-up supply from the public mains (e.g. a gravity system), then the plumber must notify the Local Water Authority. The minimum requirements are a site plan, a schematic drawing of the plumbing layout and details of what is proposed. The Local Water Authority must inspect at first fix and second fix stages.
7. What happens if the outlet pipes on the tank are wrongly connected up?
There are several outlet pipes on the underground tank. Follow manufacturer’s guidelines to ensure that the correct pipes are connected. Misconnecting the pump for the tank to the wrong pipe will mean it is operational, but not pumping water.
8. Anything else worth considering?  
It pays to make an early decision on the location of the control panels for the rainwater system to give the householder reasonable access.
Houses built to Code Level 5 or 6 are likely to have a number of energy-or water-saving technologies installed, including air source/ground source heat pumps, or solar panels, so do allow for the fact that all of which have control panels which will have to be accommodated.
9. Is there any specialist training available?
Yes. Along with others in the industry, we have recognised that there is potential for confusion and have therefore invested in appropriate training courses for installers. The Sevenoaks Training Academy run a BPEC Rainwater Harvesting course which was designed in partnership with BPEC and the Rainwater Harvesting Association. On completion of this course, students should be able to identify, select and install the most appropriate rainwater harvesting system.
We also offer bespoke training and advice for anyone working on large contracts, bringing people together from groundworks, site managers, plumbers, and electricians.
To find out more, or to discuss any aspect of installation and best practice, please email sustainablewater@kingspanenviro.com
[author image=”https://www.installeronline.co.uk/wp-content/uploads/2014/01/gatford.jpg” ]Adrian Gatford has more than 30 years’ industry experience in the plumbing and heating manufacturing sector working for blue chip companies. He joined Kingspan Environmental in 2010 and has been instrumental in ensuring their solutions, including rainwater harvesting, are well received by Kingspan customers in what he sees as new opportunities.[/author]