Maximum length of soil pipe under floor boards

Paul Caveill · 26 Nov 2015

Hi looking to run a soil pipe under the floorboards (Which run in the same direction) from one side of the house to another. The length would be 6.5m and I would want to connect into existing stack. The floor joists are 7 inch in depth. Would also want to connect a shower and sink but the WC would be at the furthest point. Can this technically be done within the current regulations.

Currently the en-suite does not have wc and the shower and sink are connected into the rainwater pipe on the same side of the house which I believe is wrong?

Thanks in advance

ree · 26 Nov 2015

Presuming that you have room to crawl under the floor what you propose is no problem. 6m is the Regs but 500mm extra is no sweat - keep the fall at about 18mm to 20mm per meter.

There's no problem with the basin and shower going into the RWP gulley or the RWP itself. The Regs dont want rainwater introduced into the main sewage system.

AlanE · 26 Nov 2015

Paul reading your original post you say 'floorboards' run in same direction. If this is correct then you will need to cut the joists virtually their full height which would obviously be a no-no.

Did you really mean the JOISTS run in the same direction? In which the project may be doable.

ree · 26 Nov 2015

You wouldn't need to cut the joists, no matter which way they run - simply hang the pipe below the joists which is the best place for it. The total drop would only be about 120mm.

Agile · 26 Nov 2015

ree said:
There's no problem with the basin and shower going into the RWP gulley or the RWP itself. The Regs dont want rainwater introduced into the main sewage system.

I don't think the local water authority or the Environmental Agency would want soapy water going into the nearby streams and rivers and killing all the fish!

ree · 27 Nov 2015

We dont know where the drainage is discharging to?

If the discharge was to a sump the waste would be strained and spread.

Direct discharge from a residence to a waterway is no longer common.

I doubt that any soapy water from the OP's en-suite would "kill all the fish" (all?) in "streams" (plural) and "rivers" (plural) - rather a drama queen bit of hysterical language.

PullerGas · 27 Nov 2015

ree said:
We dont know where the drainage is discharging to?

If the discharge was to a sump the waste would be strained and spread.

Direct discharge from a residence to a waterway is no longer common.

I doubt that any soapy water from the OP's en-suite would "kill all the fish" (all?) in "streams" (plural) and "rivers" (plural) - rather a drama queen bit of hysterical language.

What are you getting your knickers in a twist for!! It's not even your job!!
Tony's right, you can't put waste water into a rainwater system of any kind. Some older houses had common soil & rainwater drains. But anything built after the 50s is likely to have either a dedicated RW system running to streams etc or run to soakaways.

Newboy · 27 Nov 2015

Plain and simple - it's illegal to discharge foul water into the rainwater system

http://www.connectright.org.uk/questions

Paul Caveill · 27 Nov 2015

Thanks for your feed back, My intentions were if possible to add a WC into the En Suite by running the Soil pipe into the existing stack that currently resides on the opposite side of the house. the Joists run in the same direction as the intended route of the soil pipe and with 7 inches between the floor level and the ceiling. But it would be run of 6.5M. I calculated 0.08m(max drop i could get) over 6.5 =0.012 which if i'm correct gives 1 in 83 gradient? I would then connect shower and Sink into this. Currently the bathroom and downstairs WC are above each other i was wondering if;
A the 6.5m Run at that drop is possible.
B if the soil pipe dropped out of the ceiling in the downstairs WC i could come across the wall slightly to then connect into the stack or if it has to go directly into the stack, just in case the joists don't directly line up between the location of WC and stack.

i could reconfigure the en-suite so that the WC is 6m if that's better and place the shower and sink at the 6.5 M distance connecting into the WC if thats better from a regs perspective but the layout wouldn't be as ideal.

Does this make sense?

Thanks again

Paul Caveill · 27 Nov 2015

1 last thing i assume that a macerator is my last option if above suggestion isn't feasible/recommended and all three units could be connected and run to the soil pipe as they allow for greater distances?

Would ave to make sure that the En-Suite WC is for number 1s only

muggles · 27 Nov 2015

Absolute minimum fall on a soil pipe is 19mm per metre, recommended is 44mm per metre. Don't forget fittings allowance as they're bigger than the pipe, so I doubt very much if you'll achieve the minimum fall let alone the recommended fall

6m is the maximum unventilated run permitted by Building Regs. I really wouldn't recommend going shallower than the minimum fall and longer than the maximum run, that's asking for blockages

A macerator might be the most sensible option here. No reason why you can't use it for number twos

ree · 27 Nov 2015

AlanE,

My apologies, i assumed that the joists were ground floor - with them being upper floor then, as you said, joist direction is important.

Hugh Jaleak · 27 Nov 2015

You can get away with as little as a 1:100 fall provided the pipe is dead straight, and the fall is constant, your 1:83 should be ok. it would be better if you can fit an Air admittance valve at the head of the run, above the basin spillover level for good measure.

As others have said, 'grey water', (shower and basin) into a rainwater drain is strictly forbidden, and illegal. If found to be cross connected the water company can force you to have the drainage system corrected at your expense!

ree · 27 Nov 2015

PullerGas,

I quote myself:" We dont know where the drainage is discharging to". Do you?

Ignoring the excited exclamation marks - a sure sign of one who has his "knickers in a twist!!" - you say: "Its not even your job!!"
Whaddaya know? Local hysteric plays Mystic Meg. What exactly do you mean by "your job"?

In my first post, I was too tired and lazy to inquire into what kind of system the OP had - i should have, i apologise.
Regs offer discharging rainwater into a sewer as a discharge possibility.
Homes with combined systems are not required to retro split them.

ree · 27 Nov 2015

muggles,

I quote myself: " 6m is the Regs " - and FWIW i've exceeded it a number of times, once hanging the soil pipe below the joists for 12m and no come backs the last i heard. Go figure?
Experience says that exceeding the Regs by 500mm at min. fall will no way be "asking for blockages".
Experience will sometimes use the Regs as guidance just as BCO's so often do.

A macerator anywhere is a bad choice IMO, a macerator thro 6m of a first floor ceiling sounds like a very bad option.

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Maximum length of soil pipe under floor boards

Newboy

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