Knowledge: Rainwater harvesting
Market liquidity
Brian Pickworth, technical manager at Kingspan Klargester, and chair of the UK
Rainwater Harvesting Association , talks REI through safe and effective installation
of rainwater harvesting systems
A
fter the wettest winter since records began in 1910, and
extensive fl ooding causing misery for thousands of home-
and business-owners across the country, there is little
doubt that we need to fi nd better ways of managing our
water resources.
Like it or not, climate change has dramatically altered our weather
patterns in recent years, causing warmer, wetter winters and hotter,
drier summers.
The UK needs to have tailored, localised strategies both to reduce
the impact of future droughts and to lower the risk of future fl ooding.
Part of this strategy will be storing and reusing rainwater in-situ,
bringing fi nancial benefi ts to users, but also providing a much needed
water source in drought conditions
Why rainwater harvesting?
Part G of the Building Regulations now requires that water
consumption is limited to 125 litres per person, per day. Capturing
and recycling rainwater for non-potable uses such as fl ushing loos
or cleaning clothes, can reduce the amount of water used within a
domestic setting by more than 50 percent, and by up to 85 percent for a
commercial building.
However, an interest in rainwater harvesting goes beyond a drive
for more sensible use of mains water. Rainwater harvesting systems
reduce surface run-off during heavy rainfall and pass the recycled
water indirectly via WCs, washing machines etc. to the foul system
rather than the storm drains, so that it poses no contribution to fl ood
risk.
plumbing is already part-complete which can mean costly rebuilding
work to reconfi gure the system.
Having a technical team from the supplier on-site also ensures
effective co-ordination of the three trades required to install a system
correctly: ground-workers, plumbers, and electricians.
Water regulations
You should be aware that 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 available through merchants - while potable
water pipes in the house are copper, white or external to the
house blue
• The pipework must also be labelled every 500 mm externally
• Type AA or AB air gap in the system is required to avoid any
contamination of mains water supplies
How does it work?
Rainwater is collected from the roof of the building and fi ltered before
entering either an above or below ground rainwater holding tank.
The water can then either be pumped directly to WCs and vehicle
jet washes or to a high level header/break tank within the building
which will then service the non-potable appliances as per normal.
A third option uses a surface-mounted break tank and booster
system. This combines benefi ts of both the direct system and the
gravity system, in that the mains water back-up is directed to the break
tank.
Systems that serve WCs or washing machines are automatically
backed up with mains water at no inconvenience to the homeowner.
Designing a system
Bringing in expertise from the company supplying the system at
the very beginning of the project planning will enable you to assess
your best options. Unfortunately, all too often this happens when the
Pipe dream: Rainwater harvesting can reduce mains water usage in
a domestic setting by 50 percent, and more when used in commercial
environments
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