Short length of 110mm soil stack above screed

[MortarThePoint]

I have about 30mm of 110mm soil pipe to connect my stack to. It passes through the screed and a membrane and that's what I am left to work with. There's a photo below. Once I have cleaned the gaffer tape residue off, I figure I have 3 options:

1. Pushfit double socket: Floplast SP105 the stub of 110mm pipe wouldn't push all the way home but would be at least 15mm past the rubber seal. I could creep under the weight of the stack above and so move down over time. I wouldn't want the rubber seal to contact the membrane that us taped to the side of the stub.
   
    
2. Solvent weld / pushfit coupler: Floplast SP124 The sub wouldn't push all the way to the end stop, but would have ~30mm worth of solvent joint which is similar to what they have on their short 3-boss. It's pretty committed though as if I make a hash of the solvent weld I am stuffed.
   
    
3. Universal Pipe Connector: Floplast SP140 this would push into the stub and so have no limitations as they are external. It restricts the interior diameter though.
    

Is there no issue with using a ring seal onto a lower pipe? Are they more likely to leak that way?

 

The black is from when I pushed a ring seal over before during testing.

 

[Big Jimbo]

I would prefer the solweld. You can also get around the inside when it is fitted, and run another couple of beads around.

[MortarThePoint]

26 minutes ago, Big Jimbo said:

I would prefer the solweld. You can also get around the inside when it is fitted, and run another couple of beads around.

 

Beads of solvent, or a sealant?

[Big Jimbo]

run the solvent around the inside where the pipe comes into the fitting. Wipe off the excess. Do it a couple of times.

[Crunchynut]

Looking at how scuffed the pipe appears to be I would be nervous that a push fit might not form an effective seal. 

[Dave Jones]

pull it out the restbend and use a longer length ?

[crispy_wafer]

agree with @Dave Jones pull it out if you can. I'd replace with a piece with a socket on the end.  However, since it's screeded and taped up it probably won't want to come out without a fight, you could core round the pipe and remove some screed, or chip away (probably safer) to expose a bit more pipe, use a coupler and if you are concerned about the seal, plenty of CT1 round the inside?

[MortarThePoint]

31 minutes ago, Dave Jones said:

pull it out the restbend and use a longer length ?

3 minutes ago, crispy_wafer said:

agree with @Dave Jones pull it out if you can. I'd replace with a piece with a socket on the end.  However, since it's screeded and taped up it probably won't want to come out without a fight, you could core round the pipe and remove some screed, or chip away (probably safer) to expose a bit more pipe, use a coupler and if you are concerned about the seal, plenty of CT1 round the inside?

 

I won't be able to remove it due to the membrane, so it's a matter of working with what I've got. I share the concern about a ring seal. Solvent weld feels like the most robust solution. There's an amount of clear pipe available that is comparable to the insertion depth of a short boss. It won't hit and end stop which is a bore, but the solvent bond should be strong enough to support the stack shouldn't it?

[MortarThePoint]

43 minutes ago, Crunchynut said:

Looking at how scuffed the pipe appears to be I would be nervous that a push fit might not form an effective seal. 

 

I am hoping I can clean it up well enough for the solvent bond.

[MortarThePoint]

I spoke to Floplast and they thought the SP124 was the way to go. I asked if there was a part that mated on the inside of the pipe and he said Floplast didn't produce one but hinted that others may. Is this something anyone has come across. It would be a bit like a downpipe coupler, goes inside the bottom pipe and outside the top pipe. It would hopefully solvent weld on the bottom side and either solvent weld of ring seal on he top pipe.

[Dave Jones]

dont want to be putting anything inside the pipe really.

[crispy_wafer]

Sol weld should do a decent job to be fair with the SP124, it's not like you need to mark angles and set, clean up the pipe, use some of that stuff to prep the pipe(sorry cant think, my brain's frazzled! ) before the sol weld, then a good dollop of sol weld, give it a good twist back and forth (apologies, you've probably done this all before).  I'd probably look to smear up the inside with some goo whether it needed or not, but that's me going OTT!

 

On a tangent, I've got an SP124 mated to a stub on my treatment plant inlet.  Rewatec have goo'd up the inside of this! 

[Crunchynut]

Solvent weld should work but I’d be worried about the state of the pipe. Alternatively maybe you could use one of those thick rubber couplers that have a jubilee clip either end. A bit unconventional but it would work.

[MortarThePoint]

50 minutes ago, Crunchynut said:

Solvent weld should work but I’d be worried about the state of the pipe. Alternatively maybe you could use one of those thick rubber couplers that have a jubilee clip either end. A bit unconventional but it would work.

 

It's actually cleaned up pretty well. I think I am going to use an OSMASoil short boss (3 port) as it has the short insertion length and all the ports are sealed so it ends up being a short insertion solvent welded coupler.

 

[MortarThePoint]

Typical that I put on some duct tape to protect the end of the pipe and stop stuff falling in and it's then the duct tape residue that's hard to deal with.

[MortarThePoint]

4 hours ago, MortarThePoint said:

Typical that I put on some duct tape to protect the end of the pipe and stop stuff falling in and it's then the duct tape residue that's hard to deal with.

 

These are a more sensible choice than duct tape, probably about a pound each:

OsmaDrain Temporary Site Cap 110mm 4D295

[MortarThePoint]

I'll air test the joint later, but certainly stiffened up when I was rotating to spread the solvent. I like this approach as it gives a last chance pipe attachment centred 80mm above the screed. Never know, that might come in handy. I didn't level it off, just pushed it all the way home so the next section(s) will correct the error in plumbness, which is about 3 in 100.

 

I went out to do the air test and it was still smelling so I am going to wait a few hours. I always end up testing in the dark 🙂

 

[Mr Punter]

Should you have an access fitting at the base of the stack for rodding?

[MortarThePoint]

38 minutes ago, Mr Punter said:

Should you have an access fitting at the base of the stack for rodding?

 

Is that a requirement as it will end up behind kitchen cabinets. I can always install one into this if need be.

[MortarThePoint]

@Mr Punter Are you think of one of these. I could use one of these immediately above the 3-port boss if need be.

 

OsmaSoil S/S Bossed Access Pipe:

 

Floplast SP274:

[MortarThePoint]

14 hours ago, Mr Punter said:

Should you have an access fitting at the base of the stack for rodding?

 

NHBC says:

"Rodding access in locations such as kitchen cupboards is unlikely to be acceptable as it may be below the spillage level of appliances and also would obstruct access for rodding apparatus/equipment."

 

this stack is going to go straight up to a double branch, the top port of which may well be unused and so could be access. That would be below the basin spillover levels though so still not ideal.

[Dave Jones]

14 hours ago, MortarThePoint said:

 

Is that a requirement as it will end up behind kitchen cabinets. I can always install one into this if need be.

 

no, unless its 3 stories or if the bend can be reached from any other part of the run, i.e. a chamber.

 

 

[MortarThePoint]

This is ending up as a pretty busy stack:

1. OSMA 3-boss as shown in photo at floor level
2. OSMA 3-boss at ~500mm as an emergency connection point for the utility sink if there is a problem with its independent underfloor drainage
3. OSMA 3-boss at near ceiling level (GF) for shower(50mm)
4. Floplast 45 solvent bend for offset
5. Floplast 45 solvent bend for offset
6. OSMA 3-boss at screed level (FF) for bath&basin(40mm), shower&basin(40mm)
7. Floplast Double Branch for connection to two toilets and one toilet_macerator_pipe(32mm) 
8. AAV in top port of double branch

All the 110mm up to the Double Branch is ending up as solvent weld since the OSMA 3-boss is solvent weld and I need the offset done in solvent weld to accommodate the necessary verticals. The horizontal offset is only about 80mm, but moves the stack further from the corner allowing an OSMA Tight Bend (4S160) to fit in one side of the Double Branch. Rodding should be possible by removing the AAV and will hopefully pass easily through the offset.

 

I'm a bit nervous having solvent weld all the way up to and including the bottom joint of the the Double Branch. I could move the offset below the ceiling boss and do it in pushfit, but that would increase the size of the box-in in GF (300mm x 220mm -> 380mm x 220mm). Alternatively, I could add an otherwise unnecessary pushfit joint just below the ceiling OSMA 3-boss.

 

What would you do. Not worry about it, add an extra pushfit joint below the ceiling OSMA 3-boss of add a pushfit joint between the offset and the floor level 3-boss?

 

The code in the table is (lower 3-boss) - (bend) - (upper 3-boss) and Ring(F) is a Floplast ring seal 3-boss and Solvent(F) is a Floplast solvent weld one.

[MortarThePoint]

Another wildcard option is to use a ring-seal 3-boss below the offset, but that lowers the shower's connection point by about 100mm. That could be OK by using two 90 bends.

 

That might be a bit brutal for the shower flow. An alternative would be a 90 elbow out of the boss to a 45 elbow, but that increases the box-in locally

 

Maybe 3no. 45 elbows?

Edited September 6, 2023 by MortarThePoint

[MortarThePoint]

Hmm, screed is actually 52mm and pan connector is 180mm. Also A and B are the wrong way round in targets

Edited September 7, 2023 by MortarThePoint