Plugging a Waste Outlet in Soil Pipe.

[slangivar]

I am redoing my downstairs loo. This involves moving the location of the sink so I will add a waste pipe boss behind the loo and I need to block up the old waste pipe feed into the soil pipe under the floor. I thought this would be so pulled out the existing pipe and put in a 40mm plug:


The problem is that the pipe is 43mm solvent weld and the seal is about 50 years old so the 40mm plug is loose. It doesn't fall out but any positive pressure in the soil pipe will cause it to pop out.

The outside diameter of the hole where the seal fits is 48mm so I can't just buy a new 50mm adapter:

I don't especially want to buy a 2m length of solvent weld pipe and a cap, partly for the amount of waste and partly because it seems that it will just fill with sludge from the waste pipe. So my question is where can I buy a 43mm plug or is there another product which I can use to plug this hole or get the 40mm plug to fit tightly?

As you can see from this final picture the current waste inlet is under the joists so will be totally inaccessible once the job is complete.

 

[mikeey84]

Would this work

Polypipe 40mm (43mm) ABS Solvent Weld Waste System Socket Plug - Grey | MJ Plastics & Plumbing

Polypipe Solvent Weld Waste Pipe 40mm has a physical diameter of 43mm.

mjplastics.co.uk

 

[slangivar]

Thanks, unfortunately I think that is designed to be welded inside 43mm SW pipe. So wouldn't be suitable in this instance as I need something to replace the 43mm pipe.

 

[mikeey84]

Ah, OK.

Could you glue the plug in that you have in there at the moment?

 

[slangivar]

Now you're talking. The pipe that's in there has been painted so very hard to add a cap but it should be fine to plug.

Not sure why I didn't think of that after your first suggestion.

 

[kp00110]

If you are able would it also be good to rotate 90 degrees so the stub is on top of the pipe? I cant imagine its good to have a horizontal stub/old feed that could catch debris etc

 

[Nige F]

As above - plus you could secure the glued plug with a couple of cable ties joined to make a long one

 

[slangivar]

Thanks. I popped into Wolseley to see if they had one and they sold me one of these which seems to do the job nicely:

Center CB ABS access cap 40mm | Wolseley

Looking for a Center CB Socket CA2B? Order from Wolseley today - free delivery or click and collect available nationwide.

www.wolseley.co.uk

It pushed in with a little silicone spray and definitely doesn't want to come out again.

 

[slangivar]

If you are able would it also be good to rotate 90 degrees so the stub is on top of the pipe? I cant imagine its good to have a horizontal stub/old feed that could catch debris etc

I've tried my best to rotate it but it's jammed solid. I thought of putting something in the hole to provide leverage but don't want to risk damaging the soil pipe.

Any hints on how I might rotate it?

 

[Hugh Jaleak]

If it's that tight, I'd leave well alone. Provided you've got the redundant boss firmly plugged, then you should be ok hopefully. If the pipework is 50 years old, the seals in the joints will be well past their best, any disturbance may cause them to leak, giving you an even bigger headache....

 

[slangivar]

I'll do that then. I've tried enough force that the soil pipe is flexing where it goes underground and that's the limit of my risk appetite. Would there be any advantage to adding some silicone to the plug on the cap to assist the seal in the boss?