Strange sewage smell coming from behind kitchen sink cupboard

[Steven Southern]

any help would be gratefully accepted. We’ve had a single storey extension to the rear with toilet. Now we have a strange sewage like odour coming from behind the kitchen sink but not this side of the trap. The sink waste along with the new bathroom waste all now go into the soil pipe which in turn is now enclosed in the extension. The soil stack is now a plastic one instead of a cast iron one which has a cap or air admittance valve on top. This has also been shortened by about 5 feet and no longer goes through the waves and onto the roof. There is also a new manhole which I haven’t checked if it’s blocked but I wouldn’t think so as it’s only weeks old. (I’ll lift the lid and check at the weekend) once again thanks for any help. Steve.

 

[Ben-gee]

Get the builder back. If it’s only just finished, could be s bung left in?

 

[Welder]

Get the builder back. If it’s only just finished, could be s bung left in?

Couuld be the the 'builders bodge' aka an AAV? Why oh why don't they do things properly and let the darn thing breath as designed...

 

[Steven Southern]

Thing is. We’ve also had the kitchen done and we didn’t notice the smell before. But there’s only 2 weeks difference in finishing times. Could it be the aav or kitchen fitter? Would A plumber be able to tell without ripping the plaster stud wall down to access the pipes?

 

[Steven Southern]

Thing is. We’ve also had the kitchen done and we didn’t notice the smell before. But there’s only 2 weeks difference in finishing times. Could it be the aav or kitchen fitter? Would A plumber be able to tell without ripping the plaster stud wall down to access the pipes?

Would I be able to remove the aav and leave it off without any problems? Like before it was fitted.

 

[Pickwickpick]

It could be the AAV, is it easily accessible?

 

[Steven Southern]

It could be the AAV, is it easily accessible?

Yes it’s on top of the new extension roof.

 

[Pickwickpick]

Although just re reading things, I take it the AAV isn't where the bad smell is noticeable? In which case its probably more likely to be something else, but without being out there its hard to say. A plumber should be able to narrow it down to a few possibilities but from what you've said about your setup I doubt they'll be able to confirm let alone fix it without some plasterboard being removed I'm afraid./

 

[Welder]

The point PW is that the AAV will not let foul gases out not that its faulty. The point of a soils stack is to let air both in AND out. If its blocked by a poxy AAV then it WILL come out elsewhere. End of.

If this were my place, then I'd simply take the thing off first. If the problem goes away then get the builder back to repipe it properly to 1m above the nearest opening window as the regs say. AAVs are a rubbish builders bodge.

 

[Steven Southern]

The point PW is that the AAV will not let foul gases out not that its faulty. The point of a soils stack is to let air both in AND out. If its blocked by a poxy AAV then it WILL come out elsewhere. End of.

If this were my place, then I'd simply take the thing off first. If the problem goes away then get the builder back to repipe it properly to 1m above the nearest opening window as the regs say. AAVs are a rubbish builders bodge.

Cheers I’ll remove that then as soon as I’m home. Then I suppose wait to see if the gases disperse.

 

[Pickwickpick]

The point PW is that the AAV will not let foul gases out not that its faulty. The point of a soils stack is to let air both in AND out. If its blocked by a poxy AAV then it WILL come out elsewhere. End of.

If this were my place, then I'd simply take the thing off first. If the problem goes away then get the builder back to repipe it properly to 1m above the nearest opening window as the regs say. AAVs are a rubbish builders bodge.

Yes they're not meant to let foul gases out, but they can if faulty but its a moot point here. Agree with you that they're a crap bodge with potential to cause a lot of headache solely so the builder can avoid doing fitting the soil stack properly.

If the AAV is blocking it and its letting foul air out elsewhere isn't this potentially indicating an issue with the soil stack, i.e. if it can less gases out within the house it could also let waste water seep out? Suppose its prob more likely that the foul air is being forced through water traps due to pressure probs if blocked by aav.

 

[Welder]

If the AAV is blocking it and its letting foul air out elsewhere isn't this potentially indicating an issue with the soil stack, i.e. if it can less gases out within the house it could also let waste water seep out? Suppose its prob more likely that the foul air is being forced through water traps due to pressure probs if blocked by aav.

Maybe. Without knowing all the layout we can't be sure this isn't the only foul gas exit. Designers don't generally put in what's not needed. If it's the only outlet then it perfectly normal for gases to escape elsewhere as sewers need to breathe. Once again we have no idea of runs etc. With so many traps being shallow these days, it WILL find its way out. Just takes more of a build up to overcome a deeper trap.

 

[Steven Southern]

Right so I’ve cut the aav off as it was welded on and I’ll replace that with a bend and extend it up past the gutter as it was before. The pipes are as shown in the pics. I’ve lifted the manhole and it doesn’t appear blocked but I could be wrong. (The debris you can see fell in when I lifted the lid)

 

[Pickwickpick]

Is that standing water in the manhole?

 

[Old Account]

Quite a bit of builders crap in the drains.

 

[Steven Southern]

Is that standing water in the manhole?

It’s moving but slowly. That’s with the kitchen taps on full.

Quite a bit of builders crap in the drains.

Yeah I thought that. The part brick and a bit of debris fell in as I opened the lid and the water is slightly flowing with the kitchen taps on. (Not sure how fast the flow should be)

 

[WC1]

It's not really a question of how fast the flow should be. The fall on the pipe should not allow any standing or sluggish water. There's a blockage somewhere. Clear out that debris. If you've had your dinner and you're up for it, lift the next lid on the run. Watch out for Mr Rat. Enjoy

 

[Steven Southern]

It's not really a question of how fast the flow should be. The fall on the pipe should not allow any standing or sluggish water. There's a blockage somewhere. Clear out that debris. If you've had your dinner and you're up for it, lift the next lid on the run. Watch out for Mr Rat. Enjoy

So I’ve been and bought some rods today and cleared the manhole. Got some old peices of the cast iron soil pipe out the the builder obviously dropped when he was fitting the plastic pipe. Plus a few other odds n hens. Literally. Lol. Now I’ll suppose it’s how long I have to wait before the smell disperses from behind the sink.

 

[WC1]

Well done Steve! Good job. Keep an eye on it, I'd lift the lid again in a few days. If they're your fist set of rods remember to always turn clockwise. Always clockwise

 

[Sharp Point]

Couuld be the the 'builders bodge' aka an AAV? Why oh why don't they do things properly and let the darn thing breath as designed...

Builders know how to do everything..... don’t you know that YD

 

[Steven Southern]

So now everything is unblocked. How long would it normally take for the smell from behind the sink disappear. It’s not coming from the plug hole.

 

[Chuck]

So now everything is unblocked. How long would it normally take for the smell from behind the sink disappear. It’s not coming from the plug hole.

How long is a piece of string?

Unless you have some way of blasting fresh air through all the voids where the smell is lingering it will gradually diminish and lose a certain proportion of its concentration day-by-day.

My worry, and I'm always a pessimist when it comes to drains, would be that the root cause of the smell is a leaky drain and the blockage forced sewage out through the leak into the surrounding ground. If this is the case it will take as long as it takes for the ground to dry out.

If I owned this problem and the smell hung around for more than a week or so, I'd be considering having a CCTV inspection and a leak test. As I said, I am a bit of a pessimist, but a builder that left the drains in the condition you found them in is IME likely to have cut other corners. In these days of 'polluter pays', you really don't want to have a foul drain leaking into the ground for years.

 

[WC1]

Hi Steve, has the manhole beeen cut to let in the white pipe on that picture? If so then the blockage filled up the manhole until it found its way out through that opening!!

 

[Steven Southern]

Hi Steve, has the manhole beeen cut to let in the white pipe on that picture? If so then the blockage filled up the manhole until it found its way out through that opening!!

Yes it has been cut although that’s the only clean bit. It’s a gas pipe apparently.

 

[WC1]

U nfortunately there's definitely a bit of a problem there . It's just not possible to cut into an insepction chamber in that way. Debris will always be falling in and blocking the pipe (aided by rats), sewage will then be leaking out into the ground causing a potential health hazard. It will need sorting.

 

[Pickwickpick]

If that's soil that is visible between the white pipe and the black plastic you might want to think about sealing it to avoid any soil getting into the drains and causing another blockage

 

[Pickwickpick]

Also just another thought you want to make sure that whatever you sell it with rats can't get through (could get some wire mesh I'm there) as they're drawn to sewers and could cause even more problems.

 

[WC1]

As the integrity of the I/C has been breached significantly and the gas pipe has been exposed... I'm out... Good luck

 

[Steven Southern]

So. A week or so has past and we’re waiting for the smell to disperse. A strange update that the smell is mainly concentrated to behind the sink and totally goes when the window is open. (But it’s not going out the window) comes back minutes after the window is shut. Strange.

 

[WC1]

Airflow is coming in the open window and pushing the smell back down behind the sink where there is an opening down to where the sewage leak is - the opening from which the sewage usually smell issues. Have you lifted the lids on that run again yet? I know I said i was out but I can't not see a problem through to the end.

 

[Steven Southern]

Yes I’ve been and looked today in the light. All appears well. Could the fact that the lid isn’t fully sealed (we’re waiting til the new year for the flagging to be done) be a contributing factor with pushing the sewage smell up the drains? With the air getting in from the lid. Cheers for the help.

 

[Pickwickpick]

No it won't be that even with the manhole cover removed it shouldn't create any smells in your kitchen. When you say the smell is behind the sink, do you mean at kitchen counter top level, or in the cuboards underneath?

 

[Steven Southern]

No it won't be that even with the manhole cover removed it shouldn't create any smells in your kitchen. When you say the smell is behind the sink, do you mean at kitchen counter top level, or in the cuboards underneath?

It appears to come from behind the trap where it would go outside but obviously it goes into the false wall now.

 

[Pickwickpick]

Any chance of a picture? Sounds to me like its an issue with the trap or the pipe work that joins it. Is there any smell coming from the sink hole?

 

[Steven Southern]

Any chance of a picture? Sounds to me like its an issue with the trap or the pipe work that joins it. Is there any smell coming from the sink hole?

There’s no smell from the sink hole.

 

[Chuck]

we’re waiting til the new year for the flagging to be done.

Don't complete the flagging until you had the gas pipe relaid in a position that complies with the regulations. Underground works are not my thing, but I am sure that you are not allowed to have a gas supply cutting though an inspection pit in the way yours has been.

You will need to follow the 'move a gas supply' procedures published by your network supplier. From memory of a job I've only dealt with once some years ago, the gas pipe will need to be made of approved materials and marked with warning tape, and end up 18 inches deep in a trench surrounded by (6 inches?) sand and no closer than 12 inches to other services.

Whoever did your current work, IMO, should be prosecuted. A rat will happy chew through that pipe and fill you drains with gas. If you knowingly leave it like it is, IMO, you should be prosecuted too.

Once the gas pipe is relaid safely, as I said before, you need your drains properly leak tested. It wouldn't surprise me if all the new stuff needs to be excavated and redone by someone competent.

 

[WC1]

Your water board will have a list of underground contractors who will be able to help. You might want to look at something like household insurence to help you make some sort of claim against the guys who left it like this state, scandalous, IMO. If someone made an honest mistake I'd usually say get them back and give them a chance to put it right, but not in this case. I'd keep lifting the lid every few days because you won't know if it's blocked because the waste will just leak out by the gas pipe. (which is one reason why you can't just cut into an I/C) - and it will block again because of the soil falling in at the breach. Look on the bright side, you found it, and you can put it right rather than building contol, the water board or some other body finding it - that could have caused you serious issues. You've come to the right place to get some input and you should be able to recover the cost from the other side. Merry Xmas to All and best wishes for the new year, WC1