Surface water drains

[Paul5152]

We moved into a new (old) house a year ago. It was built in about 1910 and has been heavily extended since (before we moved in).
The roof gutters are weird. Most drain into the 'main' drains, which go to our septic tank. One half of the roof drains down a downpipe which empties straight onto the soil at the top end of the house (the house is on sloping ground with a terraced garden).

Obviously none of this is ideal. We did have a problem with ground water coming up in the 'basement' (actually 'a garage under the house, lower down the hill') last winter, which may have been exacerbated by the unterminated drain at the top of the house.


Another "problem" is that the bedrock here is literally about 30-40cm underground. That means that putting a soakaway in wouldn't be a trivial job (and it wouldn't soak away very well).

So, my current thinking is - divert all the downpipes into water butts which we can use for watering the garden and potentially washing cars (after filtering), and simply divert any overflow from them onto our garden about 2 or 3 metres downhill from the house.

Even installing proper underground pipes would be tricky because of the shallow bedrock

I'm not sure what buildings regs says about this, or if there are any better suggestions?

 

[avonmouth]

Your house sounds exactly like mine.
I have 1/3rd going into a soakaway,1/3rd going into my septic tank and 1/3rd going into a rainwater butt that then overflows down a slope and away from the house.
I don't find it much of a problem and have no option with regards the septic tank.
I do have an exemption certificate that allows 2 cubic metres per day to overflow from my septic tank although this is not measured by anyone.

 

[Hugh Jaleak]

Rainwater into a septic tank is never a good idea, high flows in times of heavy rain will stir the contents of the tank up and wash solids into the outfall and/or soakaway/leachfield, soon rendering that useless.

If you're happy to collect water in Butts, and allow the excess to drain onto the garden, I doubt anyone at Building Control will give it a second glance. Main issue to to keep the rainwater away from the Property.

 

[Ivor Windybottom]

You shouldn't have any rainwater at all going into a septic tank for the reasons given above. Ours was like this when we bought the place, the bloke whose land it emptied onto was not happy with the situation. I had to go into the ditch it emptied into to unblock it, I can confirm that it definitely does rinse some nasty stuff straight through the septic tank.

Ours is now combined, but on the opposite side of the septic tank (now replaced with a new sewage treatment system). So the treated sewage gets combined with the rainwater, which all goes down one pipe. It works really well, the rainwater gives the pipe a good cleanout and keeps it fresh. You could also do the same with a percolation system.

You've got a big project ahead of you. Sometimes rock can be a good thing - it may have fissures in that will take vast amounts of water if you place perforated pipes over them. It's definitely preferable to clay, which is pretty much useless for a soakaway.

I'd suggest looking at replacing the entire system. If it's old then probably plan to replace absloutely everything, every component and pipe. If you find that one or more parts are functional then that's a bonus. The septic tank will need completely emptying while rinsing with a hose so you can see what it consists of. Usually a load of broken up old bricks that are collapsing. Whatever it tips into is likely to be sludged up, especially as the sludge has been pushed into it by rainwater.

I replaced every part of our system. I got a groundworks company with a digger to fit the sewage treatment system, otherwise it was me and a shovel plus various other hand tools. It can be done DIY.

At our last house I built a soakaway in clay soil. It worked if the ground was really dry, otherwise it just sat there. So I put an overflow from it down to a lower part of the garden. Most of the time the soakaway did the job, but in heavy rain it would pour onto the lower garden. A bit messy but better than it backing up and spewing next to the house. You couldn't do this with treated sewage though, that would be disgusting.