UKH

OK, we live in a 50s house in the S Lakes. It was built during post-war austerity, and has had some cheapo alterations before we bought it, but generally seems sound.

A drain got blocked recently (no suprise there), one that collects rainwater from half the roof, and the drainage from the utility - though no blackwater, which is collected at the other end of the house and drains into a septic tank.

I went to clear the drain this morning (nice!), and lifted a flag next to it, which revealed a pit into which it drained. That's about 50cm square, and was about 30 cm deep, so I started to dig out the accumulated muck to a depth of about 75cm, expecting to find a pipe carrying away the waste. Instead I hit a layer of pebbles, that l assume had been put there deliberately. So, my questions are 1) was it ever common practice to just have a soakaway so close to the house, 2) is it possible that there is a pipe there so I should just keep digging and clear it, or 3) if it is a soakaway is it large enough to cope with the roof (which itself is large enough to accommodate 18 solar panels.)

The answers I would like are yes, no and yes but I'd be interested in a more expert opinion!

Soakaways are common. Probably no pipe. Current requirements are probably tighter than in the 1950s. Required volume depends on area drained and permeability of the soil. Guidance here (googling for the doc may be cheaper...)

https://www.brebookshop.com/details.jsp?id=327631

The pebbles may be overlying the pipe, depending on how big they are it’s fairly common practice to backfill around pipes with small pea type gravel. Depending on how cheap the builders were, what was available to hand, opening time on a Friday etc they may have chucked anything in. 

When you say pebbles, I’m thinking you mean smooth, round or oval stones? They are suboptimal for a soakaway. Angular stones would be more usual as they hold onto water much less than pebbles, so pebbles would be an unusual choice.

Hi Rob.

Standard practice before installing a new soakaway is to do a percolation test. 

Have you tried filling your pit with a hose pipe to see how efficient it is?

Nope, good idea (or just wait for the inevitable rain 🙁)

Assuming it does drain away quickly enough is it likely to be doing long term damage.? The house is built on more or less the continuation of Scout Scar, so pretty solid (but presumably porous) limestone.

Knowing the area, I assume your foundations are onto stable rock so unlikely to be affected.

You said the house is about 70 years old so any problems should have become apparent by now or been picked up on survey report when you bought it recently.

Soakaway engineer here, proximity to your house is an issue, it could undermine your foundations. 

Building Regulations Part H states that a soakaway must be more than 5 meters away from a building. Additionally, it should not be within 2.5 meters of a boundary or in unstable ground where the water table reaches the bottom of the soakaway at any time of the year.

I would say that it sounds like a small soakaway for modern calculations. And with the climate changing, getting wetter and more intense, things may need updating. Also new developments in the area could be effecting sub surface water in the area. 

if your in an area not served by surface water drainage then soakaways are your only option if you have the space outlined above. 

Thanks one and all. The conclusion seems to be a) it is a soakaway (I'll dig a bit more to confirm), and b) it's probably too near the house and too small for comfort.

Not sure we can get 5m away from the house -it's solid rock round here! - but in time digging a better one further away from the house seems a good option.

The fact that you're on solid rock surely means that your foundations are equally solid and, assuming that the slope of the land is in your favour (is it?) water will run off?

Modern building regs don't really help with old houses...

Yes, that would be my wife's point of view! We hope to be tidying up that end of the house next year, so might as well move the soakaway away from the house at the same time, belts and braces really. 

You might find a new soak away needs to meet current building regs while an existing one can remain. Maybe you meant repairing your existing soakaway?

Exactly. If you haven't got the requisite 5m you can't magically create more land. All you can do is comply as far as is reasonably practicable. 

Indeed!

Sounds like you have an illegal connection. I could be wrong, but I suspect if you asked the EA they would insist the grey water from the utility room connects to the septic tank.

I doubt that soakaway (if that's what it is) is original to the house. Sounds to me like bodger the badger has been in there.

I don't know when the soakaway 5m rule came in, but I expect it was known in the 50's not to place them near buildings. I bet the septic tank is at least 7m(20ft)  away from the house, 7m being the current requirement.

A lot of septic tanks have needed to be upgraded at the owners cost if they discharge direct to a watercourse so they are cracking down on this. In Wales and Scotland you have to register your tank. I'm sure England will follow before long.

I would consider routing the waste to the septic tank at some point.

Curious where the septic tank drain to (and the soakaway for that matter) if you're in solid rock. Is it very fissured, or do they just not work very well.

You're correct. Greywater should go to foul/combined sewer or septic tank/treatment plant.

Interesting points. Routing the drain to the septic tank isn't really feasible, as it's the other side of the house. And no I don't know where the surplus water from the septic tank drains to, though I have wondered... There's no visible outlet on either our or downhill properties.

Normally an outlet from septic tank to a drainage field, you can probably see the direction the outlet takes if you lift the cover/slab. Given the age of the property it may well be a rectangular brick structure covered by concrete slabs, waste goes into one chamber, water weirs over into a settling chamber that overflows into an outlet pipe.

I've only seen it once, when it was being emptied, but from memory that seems spot on! Amazing!

What are you worrying about? Just buy some shares in a water company and rake in the divvies for your pollution. 

It's a nice idea but the water companies don't appear to be interested in connecting our rural home to their sewers so that they can dump our effluent into the nearest river and it is illegal to cut out the middleman and dump it straight into the nearest convenient river

Can be a detriment.  Consider for example an old barn - now a house - with rubble stone walls, the base layer of which is big boulder stones sat on the clay.  At some point in the 1980s it gained an extension with buildings regs complaint foundations.  Boulder stones and foundations don’t respond in the same way to the change in hydration of the clay.  Problems ensue.

If we get a drought in the summer, the functional extent of the soak away may well be visible as less parched grass.

If there’s any grass left after the rains retreat…