Surface water in clay

How to deal with surface water on clay or high water table site.

When building on a clay site a number of issues can increase costs. Messy and expensive excavation, deeper foundations and biggest problem of all; rainwater will not soak away.

A simple infiltration test will soon give you the damming news; the water simply won’t shift.

In many cases you now have two options; build and absurdly large soakaway or beg your water provider to connect to the storm drain.
In virtually all cases, no matter how nicely you ask, even if they know you’re building on a clay site, you will get one of two answers;

“No, sorry our drains are at maximum capacity.”


“OK… Connect to our drains, but you’ve got to make sure the water entering the drains keeps to a sensible level.”

Fine you would think… Then you read the small print.

“When we’re taking about the rate entering the drain, we’re looking at worst case scenario; The biggest storm of 100 years, and we want to add 40% extra water to that storm in case of climate change”

Nightmare stuff… That means no ‘off the shelf’ solution will work and you (before we came along!) needing to spend thousands on drainage engineering calculations.

So the answer?

Rainwater Harvesting Ltd have developed Rain Activ a system that is especially designed to provide meet the stormwater discharge rate stipulated.
Rainwater is taken from the roof, heavily filtered, then released at a controlled rate.

Each system is calibrated bespoke to site requirement. Our professional specification team use Micro Drainage™ hydraulic calculation software to provide planning authority recognised calculations ready for submission.

All systems use our shallow dig tanks, with installation depth around 1m. Vitally important in difficult to excavate or high water table areas. Filters are fully self-cleaning with maintenance typically one visual check per year.

And the best bit – as we use the same high quality filtration and fully sealed tanks, the system can be converted for dual purpose including rainwater harvesting. So in most cases the system could end up saving you about £500/year in water rates. No other system does that!

Systems start at just £1800+VAT, including professtional specification. Saving £1000s over traditional SuDS system.


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