Reverse flow from soakaway

[James Carmichael]

Hi all,

HNY and all that.

I've installed an underground rainwater harvesting tank with an attached soakaway for any overspill.

The soakaway is a bit sluggish (slighly clay soil) but the best option I had for the time being. However, over the last few days it's been noticeable that the soakaway is draining back into the tank. This is happening because the soakaway is providing a sump for rain falling on the neighbouring garden to drain into, and the invert on the soakway in the tank is about a metre underground. Basically, in heavy rain I've got about 1 metre of neighbouring topsoil draining into the tank.

This is not the worst thing on Earth (and longer term I can do something different) but I am wondering what options I have to reduce this backflow? The best I can think of is to fit an underground non-return valve to the 110mm outflow pipe, but the only ones I can find need to be fitted into a chamber for maintenance. I will not be popular for installing yet another manhole cover in the lawn!

Any other clever plans?

Thanks

JC

 

[oldbutnotdead]

The first question to ask might be 'if I prevent this water going into my buried tank, where is it going to go?'
That will probably guide your solution...

 

[James Carmichael]

Well, the answer to that is that the water would simply remain in the topsoil (as it did before I dug the soakaway) and percolate away in its own good time.

This means I could solve this problem from the perspective of the surrounding land simply by capping off the soakaway.

The only downside is that the full tank would have nowhere to outflow excess water - although I guess the argument is that with a "reverse soakaway" it doesn't really now (and, actually, is making the issue worse as the tank is filling from two sources)!

 

[oldbutnotdead]

The joys of trying to do the (environmentally) right thing!

 

[jacko555]

My soakaway silted up. Was about 1.5k quoted to dig out and repair.
Called Water Co and asked if I could redirect the downpipes to the sewer and pay surface water charge instead.
This is how most of the neighbours are setup.
Water Co agreed. I was surprised.

Maybe do similar, if logicistics permit?

 

[James Carmichael]

Thanks. We're on a combined foul/surface drain so our water company is very resistant to new connections unless it can be proven that no other solution will work; which I guess the current shenanigans are saying about the prospects of a soakaway. I just hope their next answer won't be "close the main road out the front of your house, 40 metre dig, insert new manhole into main road, egress water into strategic surface water drain - £40k",

But that's all an argument for the future if the approach of stopping the backflow doesn't work.

FWIW, a bit of research this morning has found a supplier that does an in-tank u-bend/trap with a floating-ball-sealing-against-an-o-ring style backflow preventer built in; if that works, no need for the additional manhole ...