Moving my soil pipe and vent?

6 Aug 2022
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United Kingdom
I'm planning on moving the toilet in my bathroom along a bit from where it currently sits, but I also need to move my soil pipe vent since it now comes out too close to my new loft velux window.

Because of this it I think it makes sense to just move the soil pipe hole to where the new toilet is, but I wanted to check that what I have planned is possible...

Essentially I'll replace the whole thing with PVC, but remove the upper section, instead cutting across at an angle, and up on the other side of the bathroom window. The toilet would join half way along this angled section.

Would this be okay? If it's possible, what sort of connectors would I need to make this work?
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Ideally you want to replace as much of the iron soil pipe as possible and have your connector just above ground level. You can buy a cast iron insert, that has rubber fins and is designed to insert into a cast iron pipe.

You need to be aware of the building control requirements for soil pipe vents adjacent to windows and also ensure there are no waste water connections liable to splash back.

Note the pipe is very heavy, you really want to invest in a scaffold tower or platform for this job. Its roughly 5-10kg per Meter. so you need to grind an opening and then use a crow bar to crack the pipe and take it down in sections assuming you don't have a chain pipe cutter.
Thanks for your reply.

I was planning on removing the whole stack since I think it's pretty old and failing at various points. Fortunately I have scaffoling up for some roof work as of today which will make that much easier, so thanks for the tips on how to actaully remove it.

What do you mean by waste water connections liable to splash back?

I'll definitely be double checking the BC requirements to make sure it's okay. My main concern is connecting to a soil pipe where it runs at a 2.5 degree angle, and whether that is possible/advisable?
From the picture, I couldn't see where a sink, shower or bath waste was going to connect to the soil pipe. There are rules about how these connect in.

You can achieve the angle with a couple of 135 degree connectors and short straight.
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Your proposal looks ok to me, I'd see what state the existing connection to the drain is, underground before getting too carried away. Often find damaged rest bends at the bottom of old stacks, so it may be prudent to check the condition of that, and replace as necessary, before coming upwards.

Otherwise, the 2.5º angle will be fine, (soil bends and junctions are actually 92.5º to allow the 2.5º fall required in 'horizontal' runs of pipework). Are you planning on connecting any wastes, (e.g. bath, basin or shower) to the new stack?

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