The Brew Cabin

Hi

I've recently spent a lot of time and effort installing a couple of soakaways (plus drainage channels) into my back garden that ALWAYS floods in the winter. It was going well until the latest storms where it looks like the soakaways and channels are filling up and overflowing. This is putting the garden underwater once again.

The garden slopes towards the house, and I think I've made the mistake of putting the soakaways slightly closer than the 5m I saw in another thread.

But, is it possible to lay some other kind of pipework connecting the soakaways, under the patio, to the surface water pipes coming down from the roof ?

The house is about 13 years old, and appears to have plastic pipework for both surface and soil drains (I found enough under the garden when I put the channels in !).

Did you test whether a soakaway would work before you went to all that trouble of installing them, Dave? If your garden floods or is waterlogged for much of the year, it's highly unlikely that a soakaway is going to work, unless you have a permeable sub-strata that can be reached by the soakaway structures.

I suspect that what you've actually built is a pair of sumps, which is a gentler way of telling you that you've dug holes that fill up with water. You might be able to connect them to the existing SW system (NOT the FW system) but I can't say how feasible that is without being familiar with your garden.

If it is possible, then consider using a silt trap before connecting up to the SW system.

Tony
I did consider the fact the the water table is so high that the soakaways would fill up, but after digging them (1.5m deep) and leaving them overnight (in September) they didn't have ANY water in them by the morning. Would it be safe to assume that the water table must have been below that level then, and that it's almost impossible for it to raise by 1.5m just in a month ? (I'm not near any rivers).

HOWEVER, I live a a big London Clay area, and from the surface down I hit the following levels....
30cm topsoil, 30cm thick yellow clay, 10cm black vegetation, 80cm blue/brown mixture (hard to tell what it was, but I'm assuming now it is clay also).

I have a feeling that the soakaways are just not draining faster than the rain has been falling recently. It still is an improvement to how it was because the garden used to stay flooded all winter, but today (after 1.5 days of dry weather) there is not any standing water, although any rain will just flood it again.

I am convinced I can run some sort of pipework relatively easily under the patio pathing slabs, but I'm going to get stuck when I need to connect the pipework securely with the Surface water pipework coming down from the roof.

Thanks for all you good advice. Extremely good web site.
Dave

The level of awater table fluctuates during the year, and a rise of 1.5m is nothing compared to some locations. It depends on local geo-morphology; if you're in a clay syncline, then the rise in level can be astounding, especially after a period of heavy rain.

Your plan to link to the existing SW system is technically feasible. I would build the link as an overflow from the soakaway system, then take it via a catchpit/silt trap to a convenient point on the SW system. This may need to be a new access point or IC, depending on the exact layout, but it will be possible, one way or t'other.

So, where are you stuck?

Tony

Many thanks for the advice.
I was planning the link from the soakaway as an overflow, just below the level of topsoil. I think the soakaways are working reasonably well. and this overflow is only really going to be needed during periods of heavy rain.

A couple of questions...
1) I've not heard of a catchpit/silt trap. Could you explain ?
2) Also, what's an IC ? Is is some kind of joint ?

Now you've put my mind at rest that this is actually possible/feasible/sensible, then my main sticking point is the knowledge and ability to link in with the sw pipe system.
As you might have gathered, I'm not a builder or gardener by trade and I'm just picking this up as I go along. Therefore the thought of mucking about with existing underground SW pipes is a little bit daunting. If it requires any kind of specialist skills then I'm inclined to get an expert in(depending on how much he'll charge).

Fear of the unknown is therefore my main sticking point, especially when I might have to bring in an expert AFTER I've screwed up the underground pipes ;-)

Once again, thanks for all the great advice.

1) I've not heard of a catchpit/silt trap. Could you explain ?

See this page

2) Also, what's an IC ? Is is some kind of joint ?

IC means Inspection Chamber - See this page

Post back if you need any more help.