40mm shower waste into 110 horizontal soil branch - Allowed?

[Muzz]

I'm installing a new shower room on my 1st floor with WC.

I have calculated that I will need about a 5m horizontal branch connection to my existing soil stack and that I can get the required 18mm fall per meter.

The branch will have a couple of bends on it as it has to go out into the eaves of the house and around a 80cm by 100cm protrusion (the stairs) to reach the vertical stack located internally in the house. I will be able to make sure the bends are 45 degrees or less.

The shower is the problem, I will have to raise it, but i can't raise it high enough to get it's own waste to the vertical stack.

So my question is can I make a connection into the horizontal branch?

I had thought of a couple of ways:
1. using an equal branch, WC would use the swept part of the branch. Using some reducers i would connect the 40mm to the branch (connected to what would be the top end of the equal branch if it was being used vertically. )
2. use a standard boss of some kind straight into the 110 branch, on the top of the branch if possible, otherwise would be into the side.

Thanks in advance!

 

[Bahco]

Can I make a connection into the horizontal branch?

As long as you connect to the top I can't see why not.

 

[Richard C]

I have calculated that I will need about a 5m horizontal branch connection to my existing soil stack and that I can get the required 18mm fall per meter. The branch will have a couple of bends on it as it has to go out into the eaves of the house and around a 80cm by 100cm protrusion (the stairs) to reach the vertical stack located internally in the house. I will be able to make sure the bends are 45 degrees or less.

Getting near the lint for an unvented branch (6m); stack branches are usually straight, make sure you provide Roding access from one end or the other on those bends in order to comply with BR’s.

The shower is the problem, I will have to raise it, but i can't raise it high enough to get it's own waste to the vertical stack.
So my question is can I make a connection into the horizontal branch?

Even if you enter the main soil run at the top the top (only place to do it really), an unvented branch of that length stands a very good chance of pulling the shower trap every time you flush the loo; even if you fit an AAV on the soil branch it may still siphon unless you fit an anti-siphon trap/valve to the shower waste.

Just so you’re aware; the work your doing is notifyable, it should comply with current BR’s & that involves other aspects & not just the pipe work! You should have a compliance certificate on completion or the work will be classed as non compliant building works when you come to sell. Your LABC may also want to inspect the installation (fee involved) if a new connection to the foul drain system is involved; but, as I said, they will be looking at more than just the pipework

 

[Muzz]

Thanks for the replies.

I had wondered if this was notifiable but was thinking it wasn't as it was connecting to an exisiting stack.

I think even if i did it within the regs it wouldn't be a tidy solution.

So, I am now thinking on installing a 2nd stack which will run vertically through a downstairs wardrobe, under the bedroom floor for about 4m and connects directly into the swer pipe on my property. I will use an AAV on the top of the new stack in the eaves?

That will mean i will have about a 2.5m branch for the toilet and i should be able to boss directly into the new stack for the shower.

I reckon that will mean i need about 5-6m of 40mm for the shower and sink, which if i read the regulations correctly will mean that branch needs it's own AAV as well as it's longer thatn 3m.

I should also point out I'm in scotland, however, I've been referencing the Part H regulations from the planningportal.gov.uk site as the equivalent regulations i downloaded from the scottish sbsa.gov.uk site don't actually mention specifics like falls, pipe lengths, etc.

 

[Richard C]

I had wondered if this was notifiable but was thinking it wasn't as it was connecting to an exisiting stack.

Forming a new room with a w/c is notifyable work for the rest of us. You also have to provide forced ventilation, sound insulation in any stud wall between a room with a w/c & another habitable room & any electrical work must comply with Part P; but I don’t know about Scottish regs.

I think even if i did it within the regs it wouldn't be a tidy solution. So, I am now thinking on installing a 2nd stack which will run vertically through a downstairs wardrobe, under the bedroom floor for about 4m and connects directly into the swer pipe on my property. I will use an AAV on the top of the new stack in the eaves?

You will need to provide an inspection hatch on the sewer connection & roding access form at least one end at any change on direction although I think your allowed 1 x 45 degree bend. AAV will be ok assuming you have at least one other open vent on the system.

That will mean i will have about a 2.5m branch for the toilet and i should be able to boss directly into the new stack for the shower. I reckon that will mean i need about 5-6m of 40mm for the shower and sink, which if i read the regulations correctly will mean that branch needs it's own AAV as well as it's longer thatn 3m.

Correct; & if you run both shower & sink into the same pipe, I would make it 50mm especially if considering a pumped shower. & position the AAV so it benefits the sink or you may still find it draws the trap when you use the shower!

I should also point out I'm in scotland, however, I've been referencing the Part H regulations from the planningportal.gov.uk site as the equivalent regulations i downloaded from the scottish sbsa.gov.uk site don't actually mention specifics like falls, pipe lengths, etc.

Don’t know how the regs. differ in Scotland, something you’ll have to establish.

 

[Muzz]

Forming a new room with a w/c is notifyable work for the rest of us. You also have to provide forced ventilation, sound insulation in any stud wall between a room with a w/c & another habitable room & any electrical work must comply with Part P; but I don’t know about Scottish regs.

I've re read the regulations, looks like i can make a shower room and sink, with the drainage branch, but as soon as I add a wc it's no longer exempt. No problem though as the council lets you email them your plans and they tell you wether you need planning or a warrant.

You will need to provide an inspection hatch on the sewer connection & roding access form at least one end at any change on direction although I think your allowed 1 x 45 degree bend. AAV will be ok assuming you have at least one other open vent on the system.

i have an inspection hatch about 2m to the left with a rodding point. i wasn't planning on connecting to that point though as the angle would mean my new stack would have to make a sharp turn when it connected.

Do you need rodding access to the bottom of the vertical portion of the stack as that bit will be in the middle of the house? ( i was going to use a long radius 90 degree bend here)

 

[Richard C]

I've re read the regulations, looks like i can make a shower room and sink, with the drainage branch, but as soon as I add a wc it's no longer exempt.

More or less the same here.

i have an inspection hatch about 2m to the left with a rodding point. i wasn't planning on connecting to that point though as the angle would mean my new stack would have to make a sharp turn when it connected.

You need to provide roding access from at least one end each section of the drain run.

Do you need rodding access to the bottom of the vertical portion of the stack as that bit will be in the middle of the house? ( i was going to use a long radius 90 degree bend here)

A long radius bend (rest bend) is normally all you need but, as above, you must be able to rod that section of the pipe from the other end; this is normally accessible via an inspection chamber or, at least, an access branch.