Waste Pipe Connections

MOPI

I have started converting half of the integral garage to my property, where I intend to create a downstairs toilet and utility room. The garage already had a waste pipe running vertically into the room in the corner, which runs from the ensuite located directly above and into the ground of the garage. Therefore I thought it would be pretty straight forward for the plumbing. However, the existing waste pipe only has a 900mm connector within the space where I want to create my downstairs toilet (I think the connection is intended for rodding the waste pipe, rather than connecting new waste connections).

Does anyone have any experience of this sort of situation or general tips on how best to approach this? Would I need to cut out a section of the existing vertical waste pipe and replace with a section that has a minimum 100mm connector section for my toilet and utility to connect to?

Thanks in advance!

Gavin83

Yes, pretty much. You'll need to cut out a section of the existing soil stack and get something like the below:



The top bit will connect to your existing soil stack, the connection on the right will be for your new connection and the bottom will connect to the bottom of the existing soil stack. You can get a coupling collar that'll slip over the bottom of the above and also the existing soil stack. You need it to be 110mm.

You can get push fit or solvent weld. Push fit is easier but solvent weld is arguably the better connection.

Section62

MOPI said:

Does anyone have any experience of this sort of situation or general tips on how best to approach this? Would I need to cut out a section of the existing vertical waste pipe and replace with a section that has a minimum 100mm connector section for my toilet and utility to connect to?

There are restrictions on how close to the bottom of a stack you can make a connection.  To get the connection low enough to drain from a ground floor toilet typically results in a connection in the prohibited zone - the solution is often to install a separate sub-stack.

How are you handling the building regulations notification/approvals?

grumbler

I don't see how a 'branch' (T) can be added if you cannot move the the pipe up and down after cutting it, but in this case I think this can be done with at extra piece of vertical pipe and an extra 'slip' straight coupler

This one has "removable centre stop for use as slip coupling" - you can see it inside. This grey one seems to be the same

Compare to a normal fitting that cannot 'slip' - 

This is the 'branch' that you need to add in the first place, but I don't like a push-fit socket facing down. I think it's better to use a solvent-weld branch in this case

And, I see solvent-weld 'slip' couplers exist too -

Bendy_House

Section62 said:

There are restrictions on how close to the bottom of a stack you can make a connection.  To get the connection low enough to drain from a ground floor toilet typically results in a connection in the prohibited zone - the solution is often to install a separate sub-stack.

Interesting. What's the reasoning behind this, S62?

grumbler

Bendy_House said:

Section62 said:

There are restrictions on how close to the bottom of a stack you can make a connection.  To get the connection low enough to drain from a ground floor toilet typically results in a connection in the prohibited zone - the solution is often to install a separate sub-stack.

Interesting. What's the reasoning behind this, S62?

I guess this is to prevent water flowing up through the extra connection instead of flowing down.

Bendy_House

grumbler said:

Bendy_House said:

Section62 said:

There are restrictions on how close to the bottom of a stack you can make a connection.  To get the connection low enough to drain from a ground floor toilet typically results in a connection in the prohibited zone - the solution is often to install a separate sub-stack.

Interesting. What's the reasoning behind this, S62?

I guess this is to prevent water flowing up through the extra connection instead of flowing down.

I guess this is with a shared stack?

Phew - I seem to have got away with it :-) (removed downstairs loo and extended soil pipe up to serve new en-suite in loft conversion instead. Mil then moved in, so I refitted the downstairs loo for her. Would have been amused if every time I flushed my loo, she was up to her ankles in it.)

Section62

Bendy_House said:

Section62 said:

There are restrictions on how close to the bottom of a stack you can make a connection.  To get the connection low enough to drain from a ground floor toilet typically results in a connection in the prohibited zone - the solution is often to install a separate sub-stack.

Interesting. What's the reasoning behind this, S62?

It is within the anti-crossflow section of the building regs - to stop 'stuff' from one pipe accumulating in another and causing a blockage.  At the base of the stack I believe the reason is to stop bounceback of 'stuff' going into a branch connection and accumulating there.

Bendy_House said:

grumbler said:

I guess this is to prevent water flowing up through the extra connection instead of flowing down.

I guess this is with a shared stack?

Phew - I seem to have got away with it :-) (removed downstairs loo and extended soil pipe up to serve new en-suite in loft conversion instead. Mil then moved in, so I refitted the downstairs loo for her. Would have been amused if every time I flushed my loo, she was up to her ankles in it.)

If Approved Document H applies and the property is 3 storeys or fewer then the lowest branch connection has to be 450mm or more above the invert of the drain.  The difficult bit is usually working out how deep the invert of the drain is.  If you did the work more than a year ago then you've probably got away with it, if not.

However, as the purpose of the regulations is primarily to prevent blockages (not backflow) your MIL's ankles shouldn't have a problem in any event.  On the other hand one day someone may yet have a nice accumulation of 'stuff ' to clear out of the branch pipe..... if that's necessary I'm guessing you'd be that lucky person (which is when a nearby screwed access comes in handy).

Bendy_House

  Thanks.

The floor level is nicely above ground level, and the soil pipe goes well below ground level too. Pretty sure there's zero risk.

The lower loo is coming out again anyways.

stuart45

Less than 450mm also means that back pressure can empty the traps.

MOPI

Thanks everyone, that's really useful information and fills me with hope it could (fingers crossed) be straight forward(ish)!