Do I need a soakaway?

Evening all,
I have concerns that at least one of the down pipes from my house guttering (built mid 70's), goes nowhere (or to an inadequate soakaway). First I want to establish how should rainwater be managed away from the roof? I thought/assume it was generally not supposed to wash into the foul sewer?

The house has been extended at least once before we moved in, and now one since we moved in and next due to have a flat roof converted to pitched roof. The guttering from the flat roof goes into the ground with no adjoining obvious drain (what I need to do is lift some manhole covers and spray some hoses). But after heavy rain during the summer I could see water coming OUT of the ground a few metres away from the suspectly-terminated down pipe.

Clearly at the moment there's plenty of rain so the whole lot is sodden anyway. But with this aside there quite a lot of greening of concrete and moss that builds up as the water cannot drain quickly. Looking into the hole where the water meter is (back garden) there is water in there above the level of the dials (even during the summer) - I don't think it's a leaking main though as it's 6 bar pressure so would soon wash the ground away and make itself known.

Perhaps I should consider getting a soakaway dug as a part of the next building work? I do not know if the downpipes at the front also go to their own soakaway or if they go to sewer. All of the downpipes go through tarmac/slabs or concrete so I cannot easily tell. There are also no inspection covers near the downpipes.

I think the soil is clay, does this mean there's no point in having a soakaway? Is there a clever trick to easily find where these gutters are routed to? (I'm thinking something that involves food dye?) Most of the garden needs digging up and starting again, so no worries about placement. I can see moss has started to grow at the base of some new brickwork, it's only a year old - I wonder if this is an indication of sodden ground? For what it's worth, the house is on top of a hill (just opposite a water tower) so there are no brooks close by.

Nozzle

Soakaways don't work in clay soil.. you either need to dig below the clay to hit something that will allow the water to drain or look to alternative ways to route the water away..

You can CCTV survey your drains to see where they go/if they are blocked/broken etc.. may be worth looking into.. or simply dig them up

It was common to drain surface water into the foul in the 70s. And it's still allowed now if there are no alternatives. The process works on a hierarchal basis. You have to use a soakaway if conditions allow. If not you can use a surface water system if one is reasonably accessible. If not you can use the foul system.

Anyone know how "unreasonable" it has to be for a soakaway for you to be allowed surface or foul connections?

I too live on clay soil (London), and whilst we've had a lot of rain recently, I couldn't hand-on-heart say it's been outrageous - not like the South West. But I've got large pools of several (in places 10's of) cm of standing water in my garden right now - even in normal winters I get that to some extent as a regular occurrence - a few days of heavy rain and my garden starts to flood.

Static said:

Soakaways don't work in clay soil.. you either need to dig below the clay to hit something that will allow the water to drain....

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I'm not a civil engineer, or hydrologist, but I reckon if I dug down deep enough for a soakaway to work the neighbours would wonder if it was to do with HS2.


An extension is on the cards, and thus more roof space to drain - would it be useful to take photos of the current conditions to support a case to not have a soakaway, or is it likely that Building Control will be fully aware of the reality?

Dead simple. You carry out a percolation test. See link below. If the value is below the prescribed limit the soil is unsuitable. A soakaway must also be minimum 5m away from a building and 2m away from a boundary. If you can't achieve that your site is unsuitable and you move to the next option.

http://www.eden.gov.uk/planning-and...nce-notes/rainwater-soakaway-design-guidance/

Hi everyone,

Thanks for the info ref the soak-away test, suitability in clay and the common 70's practice. No thanks for the thread hi-jack BaS.

The back garden is large enough to contain such a soak-away far enough from buildings and boundaries, but in this type of soil it's probably a waste of time. When the weather is drier, I'll deploy the hose down some drains and see what floods.

Nozzle

Nozzle said:

No thanks for the thread hi-jack BaS.

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You really are hard-of-thinking, aren't you.

Dye test would be first option, but may find this stuff easier than food colouring! http://www.screwfix.com/p/monument-tools-flourescein-drain-dye/31595

Separate drainage for foul and surface water were being laid in the 70's, although it often seems the rainwater was connected to the nearest convenient point, be that foul or surface water.... Chambers can be sparse on surface water systems too, which doesn't help. If dye test doesn't shed any light then CCTV may help, but that would require breaking into the drain to get the camera in.

Digging where the 'fountain' appeared would allow you to ascertain if that is in fact a soakaway or a broken pipe, either way it may provide scope for access with the CCTV should that be needed.

That powdered dye stuff looks ideal... I'll pick some up from Toolstation. Thanks for the idea

Nozzle

It's good stuff, you wont miss it when (if!) it appears. Used oodles of the stuff a few years back, dye testing an entire housing estate looking for cross connected drains. (Foul sewer was overloading in times of heavy rain.) Never did find the problem, Water Authority spent millions laying bigger sewers instead.....