I'm presently constructing a new and largish patio area. I am trying to work out the best method of ensuring that rain-water drains away easily without causing 'lakes' at the lowest end. There is a manhole to a foul-water sewer in the middle of the patio (I'm disguising it by using an inlay manhole cover). Can I drain rain-water into a foul-water sewer or is this verboten?
Kev
AIUI, this may depend on the sewerage system in your area and whether they have separate foul and rain water systems. I think the only definitive answer will come from an enquiry to your local sewerage company.
Christian.
Depends on you local water company and what ever existing drain arrangements are in place. A friend of mine had same problem with his patio, handy foul water drains (ie in patio), but no rain-water drains nearby. His (actually builders) solution was slope towards lawn, dig up area of lawn, fill with gravel with drainage pipe in bottom running 20 odd feet to rain water drain (oh an put grass back).
Works fine, I think it floods in very very heavy rain but then just drains away. I have a feeling this was done as the builder suggested grilles/drains in patios don't look nice and are always prone to blocking with leaves/garden rubbish.
Out patio slopes towards lawn and yes it floods in heavy rain, but soon soaks away in the lawn.
OK - thanks for that. My lawn slopes up away from the house and so I have to 'dig into' it in order to slope the patio down. This means that I then have to have a retaining wall at the bottom of the patio. I have considered just digging a deep trench about a foot wide between the patio at the retaining wall, filling it with rubble topped off with decorative aggregate and hoping that this 'soak-away' will be sufficient.
Kev
It's usually verboten. Even if this foul-water sewer does take existing rainwater from elsewhere, you would be adding to the load and this needs EA permits and permission from any riperian owners of the sewer.
I had a garden which from your description sloped in a similar way up from the house etc. I dug a soak. My patio wasn't huge and the ground was heavy clay. I dug a soak about two to three feet deep by about 2 feet square - pretty small. Filled it with stones, put a metal grill on top of the stones, and laid the sods back down on top of that (I'd no retaining wall). There was then no evidence of there being a soak there.
In really really heavy rain it flooded and took perhaps an hour to clear. In yer average type shower it didn't flood much at all, if at all. Prior to the soak, an average shower would have left it flooded for a good couple of hours.
There's no easy way of telling whether your soak will work. I "hoped for the best" too, and pretty much got it. You might or might not.
Verboten
Just put a small slope in the patio to wherever its convenient to dump the run off.
Its pretty much a nono for all new builds I think.
It will be better than nothing.
OTOH whty not make a rill - an open gutter - to fornm a water feature and fill a pond somewhere?
Yeahh, In clay a lot depends on the local water table. After prolonged periods of heavy rain its pretty much 'at the surface' around here. water washes off any ground that isn't land-drained straight into the ditches etc. Fortunately my house and patio have been built above local ground level, and I have a french drain all around it leading to a pond lower down the garden...
[snip]
Just highjacking your post to reply to the OP....
We are on sloping ground. Any retaining wall must have drainage through it and will itself drain considerable water into a trench at it's foot. On solid clay we've had this problem, with the water filling the trench and not draining away.
Just last week I had to dig an outlet trench, (going about 18m further downhill), to a soakaway in a patch of gravelly marle. The trenches were lined with agricultural drainage pipe.... corrugated plastic pipe, perforated along it's length. Surprisingly cheap. just under a tenner for a 25m reel of about 2" diameter blue pipe.
An estate new build is very likely to have separate foul and rain sewers, though. A one off plot linked to preexisting sewers would be very different.
Christian.
Not allowed - if you get the proper fall, you can do as you suggest in another post, or put in a gulley and plastic soil pipe to a soakaway (a brick-lined covered hole in the ground *not* filled with hardcore). I would not use "Accodrain" or similar, it looks nasty. You can get special slabs cast with a shallow gutter in them, which might be useful.
Thanks for thaty Tony. I reckon I will certainly have to provide 'proper' drainage rather than a simple soak-away.
Kev
I don't know if it relevant to your area but our water rates are slightly lower than next door's. This is because I have made sure (and recorded to the water authority) that all surface drainage water off this property is dealt with by soakaways, not into their foul water system.
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