Soil pipe vent advice

I moved into a new build about 6 years ago. I’m planning to redo my bathroom so today went up to the loft to do the planning for running the ceiling rain shower arm and inspect the soil vent pipe. I was a bit surprised to find that it appears they didn’t connect the soil pipe to the actual venting roof tile. It’s quite far inside so I haven’t had a chance to go right inside to check yet but will do in the next few days. But the loft doesn’t smell or anything and from what I can briefly see they might have capped the top of the soil pipe instead of actually connecting it. I’ve attached a few pics (sorry it’s pixelated) one shows the pipe going up right next to where it should connect to the roof tile vent but I can clearly see it’s not actually connected. I’ve also attached a pic of how the vent tile looks from outside.

Question is, by the looks of it, the soil pipe doesn’t look like it 100% lines up to the vent. Is there a flexible connection that can be clamped onto this to create airtight connection ?

Thanks

Can't tell if it's a Ubbink but you need something like this, https://www.roofingsuperstore.co.uk/product/flexible-pipe-110110-for-soil-terminals.html

Looks like quite a tight fit though, you can shorten the vent pipe a bit and put a straight coupling on it.

denso13 said:

Can't tell if it's a Ubbink but you need something like this, https://www.roofingsuperstore.co.uk/product/flexible-pipe-110110-for-soil-terminals.html

Looks like quite a tight fit though, you can shorten the vent pipe a bit and put a straight coupling on it.

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Does this use a jubilee clip sort of clamp to connect over both pipes? Or does it insert over existing pipe? Just out of interest, can regular venting exhaust pipes not be used?

mderoy said:

Does this use a jubilee clip sort of clamp to connect over both pipes? Or does it insert over existing pipe?

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No clamp, socket one end and plain end on the other.

mderoy said:

Just out of interest, can regular venting exhaust pipes not be used?

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Not if you want to do it right.

So I finally managed to get into that crawl space on the corner of the loft and took a closeup photo of what I have. I’ve attached the photo. The roof vent bit is 100% open with nothing connecting to it. And the end of the vertical soil pipe has some sort of cap on it but doesn’t look like an ordinary blanking cap. Almost looks like some sort of venting cap but why would it be venting into the loft? Plus there’s never been any smell whatsoever in the loft.

Can anyone explain what this setup is please? Is this an unfinished connection? Does it need to connect to the vent pipe on the roof that’s currently open?

Does the loft space need air maybe that’s why they left that open? Would really appreciate some advice on how to tackle this.

I know for sure they everytime there is heavy rain and the road drains get full then I always get backpressure where toilet pan water rises then slowly drops because the other end isn’t open.

It's an AAV, better to connect to the external air, but you can leave it alone if everything is working as it should.

Possibly a classic case of Trades doing what was easiest at the time. Roofer has provided a Vent Tile as per their Spec I'd imagine, for Plumber to connect Soil Stack to. Plumber either hadn't got correct fittings to make said connection or simply couldn't be bothered, so terminated the Stack with an Air Admittance Valve. The AAV does exactly as it says on the tin, lets Air in, but not Out.

If all works ok, then leave as is, if odours or gurgling traps become an issue, you may have a blockage downstream, if not then maybe time to look at venting the stack.

That explains why there’s no smell in the loft. However, ever since the house was built. I’ve always had issues when there’s very heavy rain.

During heavy rainfall to the point where the roads are flooded and the drains can’t cope, I get gurgling noises from the bath drain, and the toilet water level rises and then drops again. This has been happening for years.

A few times when this happened, I opened the inspection cap on the vertical soil pipe to see if it would help. As soon as I opened it, the problem stopped straight away. Once I closed the cap again, the issue came back.

Because of this, I’m not really sure how the AAV is meant to be working.

If I wanted to connect the soil pipe directly to a roof vent that’s already there would I just remove the AAV and connect the pipe straight through to the roof? In that setup, would there be no one-way valve at all, just a direct vent to the outside air?

Is the AAV solvent welded or is it push fit? If it’s solvent then I’m assuming I’ll need to cut it out?

mderoy said:

If I wanted to connect the soil pipe directly to a roof vent that’s already there would I just remove the AAV and connect the pipe straight through to the roof?

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Yes, connect to the roof tile stub.

mderoy said:

Is the AAV solvent welded or is it push fit? If it’s solvent then I’m assuming I’ll need to cut it out?

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Glued, cut it off.

mderoy said:

That explains why there’s no smell in the loft. However, ever since the house was built. I’ve always had issues when there’s very heavy rain.

During heavy rainfall to the point where the roads are flooded and the drains can’t cope, I get gurgling noises from the bath drain, and the toilet water level rises and then drops again. This has been happening for years.

A few times when this happened, I opened the inspection cap on the vertical soil pipe to see if it would help. As soon as I opened it, the problem stopped straight away. Once I closed the cap again, the issue came back.

Because of this, I’m not really sure how the AAV is meant to be working.

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This would be due to the house drains being connected somewhere down the line to a Combined Sewer, a sewer which takes Rainwater as well as sewage. When it rains heavily the sewer will be carrying a lot more water than usual, (the Victorians designed them this way so the system got a good flush every time it rained), and so will be looking to displace air in the system.

Some of this air is being pushed back up your house drains, and cannot escape, so looks for the easiest way out, i.e. the bath and toilet. Valve does as it says on the tin, it is an 'Air Admittance Valve', it lets air in not out of he system. Removing the inspection cap will allow the pressure in the soil pipe to escape, and possibly some odour with it!

Not something I'd recommend though, apart form the risk of odour and sewer gases coming into the property, any Rodents looking for an emergency exit from potential drowning may seize the opportunity.

Given the situation I would recommend you remove the AAV, (it will need to be cut off as it's glued on), and connect the stack to the open vent. This will help the system breathe, and hopefully prevent any more gurgling issues in times of heavy rain.