Water in vent pipe

Doolittle51

I was doing some work in the attic today, and noticed a broken flexi vent pipe. Two pieces of vent pipe were attached with duct tape and this is where it broke.
One section is connected to a roof cowl and I traced the other section back to where it originates - looks like it's coming from the top of the toilet soil pipe. (I live in a duplex, so this is where the top of the soil pipe is)

The odd thing is that there's a lot of water in the vent pipe.
See attached pic - the section of vent pipe on the attic floor is full of water. Must be about 7 or 8 litres in there.
Any idea how this water got in there? It couldn't have come through the cowl because the vent pipe is probably 6 or 7 metres long, and the water has collected near the soil pipe.

Also, whats the best way to fix this? The flexi pipe is connected to a small diameter rigid pipe as you can see in the picture. I'd be tempted to replace the flexi pipe with rigid pipe if possible, solvent welded, with an decline towards the top of the soil pipe. The small diameter rigid pipe looks like bath waste pipe, but a bit bigger - haven't measured it yet. Does this type of pipe come in 50mm?

Billy Bunting

Damp air will condense in the pipe, it will need to be shortened and slopped towards the roof vent.

Stavros Murphy

Billy Bunting wrote: »

Damp air will condense in the pipe, it will need to be shortened and slopped towards the roof vent.

Twill, however a better solution and one that might be of interest to people is the fact Vent-axia do a condensation trap that goes in just above your ceiling extractor , and plumbs correctly into your overflow pipe from the attic tank - hey presto, no more dripping out of your extractor. It's a somwhat common problem as it happens as I put in two of these units only last week for people that were plagued with drips and stains on their ceilings.

gdavis

I would change to pvc pipe,glued joints,and rising all way to roof cowel

Stavros Murphy

gdavis wrote: »

I would change to pvc pipe,glued joints,and rising all way to roof cowel

This does not work however - the vapour condenses in the cold pipe and drips back down. Any ones I've done did indeed already rise to a roof cowl and still dripped - it's why vent axia make a simple condensation trap, designed for the purpose, cheap and effective. Any other solution is just trying to re-invent the wheel. They sell condensation traps for a reason.

gdavis

as it is now a solid pipe it doesn't make a difference if it condenses as it will drip back into the waste if it does,to say it doesn't work is incorrect,the flexi stuff imo is not suitable for vents from soils and will "sweat", unless of course u are working for vent axia:rolleyes:

Doolittle51

I'm sure the vent axia thing is only intended for use with extract fan ducts. This is a vent line for a soil pipe. As gdavis pointed out, what difference does it make if water drips back into the soil pipe?
I'll replace the flexi ducting with solid pipe. Can the solid pipe connect directly to the roof cowl? If not, I'll leave a short piece of flexi connected to the cowl, and connect this to the new rigid pipe.

gdavis

the cowel may take a 4 inch socket,depending on type,if not you can get a fernco coupling or similar that will connect both,,bracketed well,if it is a vent from toilet pan itself it should be run in 4 inch,