New en-suite, couple of questions on routing the waste

[Muzz]

Hi,

Been planning out an en-suite, my design has evolved based on investigations around my house and have come up with the following.

I will have an 8.5m horizontal branch (18mm fall) which runs on top of the joists in the eaves of my house, this will exit the building on the gable and will have a vertical drop a few metres upstream of my current inspection chamber. I'll make a new connection to that chamber. I'll stick an AAV at the toilet end of the branch along with rodding access.

Do I still need an external vent? my system has an internal vent pipe running through the house and out the roof, the other end ultimatly comes back to the existing inspection hatch, so not sure if a 2nd vent is needed?

Shower waste, i could either have an 8.5 metre shower waste branch connecting into this new soil outside, (don't think i could boss into the side or top near the toilet) but it would mean the shower will be 20+cm off the ground.

Or, i may be able to run the shower and sink waste down into the kitchen and connect into the trap underneath the kitchen sink. Is this allowed?

Cheers.

 

[Richard C]

I will have an 8.5m horizontal branch (18mm fall) which runs on top of the joists in the eaves of my house, this will exit the building on the gable and will have a vertical drop a few metres upstream of my current inspection chamber. I'll make a new connection to that chamber. I'll stick an AAV at the toilet end of the branch along with rodding access.

Do I still need an external vent? my system has an internal vent pipe running through the house and out the roof, the other end ultimatly comes back to the existing inspection hatch, so not sure if a 2nd vent is needed?

Both positive & negative venting is required on the foul drain system; as long as you have an existing open external vent elsewhere an AAAV will be acceptable.

Shower waste, i could either have an 8.5 metre shower waste branch connecting into this new soil outside, (don't think i could boss into the side or top near the toilet) but it would mean the shower will be 20+cm off the ground.

Maximum length of an unvented waste branch is 1.7m @ 32mm; 3m @ 40mm; 4m @ 50mm so additional AAAV will be required or you will continually draw the shower trap. If you boss into the w/c branch, you will run the risk siphoning the shower trap every time the loo is flushed. Separate connections to the stack for each waste branch is always the preferred option although you could combine the shower & sink waste run with the addition of an anti siphon trap on the sink.

Or, i may be able to run the shower and sink waste down into the kitchen and connect into the trap underneath the kitchen sink. Is this allowed?

That is bad practice; it will almost certainly exceed the maximum lengths for unvented branch runs & could possibly lead to a flood in you kitchen under certain circumstances; think about it!

Here is a link to the Building Regulations for drainage & waste in case you don’t already have them.

http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADH_2002.pdf

You should also be aware that the work you are doing is notifyable & your LABC will want to inspect for compliance (fee involved). In addition, ALL the work your doing must comply with BR’s & that includes electrics, ventilation &, in some cases, sound insulation; these regs. can be found on the same site as the above.

Just noticed your in Scotland ; BR's & notification proceedures may be different up there!

 

[Muzz]

Thanks for the reply,

Have been using the english regs as reference as the scottish equivalent doesn't mention specifics like falls, it just says comply with the relevant standards.

I will be DIY-ing it all but I do intend to notify building control, that's what my research just now is for.

If connecting to other wastes is bad practice, i guess I'll have to raise my shower plinth, not ideal, but i guess i could make it less bad by using low profile trays and traps.

 

[Muzz]

hmm, just reading up on hepv0's, looks like they are quite low profile to save a few mm and would cover the venting on my branch pipe.

anyone got any opinions on them?