Blocked Kitchen sink nightmare!

[pwoakdon]

I hope someone here might be able to shed some light on a very strange issue I have at my flat....

3 weeks ago my kitchen sinked got blocked, I tried plunging it and strong sink unblocker but neither worked. We, stupidly in hindsight, called up Plumbforce direct to get the issue resolved. Avoid them at all costs by the way. Plumber one turned up, spent about an hour plunging and used a 10m rod down the waste pipe which didn't work. Another hour of plunging and it suddenly appeared as though the problem was resolved, water drained fine. This was on a friday, I came back after a weekend away and the problem had returned. Plumbforce direct sent out another engineer, this time a drain expert. He did the same as the first guy with no luck but then noticed that we have an air admittance valve under the sink which he reckoned was faulty. Plumber 3 turned up 2 days later, replaced the valve but the issue was still there.

By this time we had not been able to use the sink or dishwasher (which is connected to the same waste pipe under the sink) for over a week. Plumbforce then stopped answering the phone so we are trying to get our money back.

Strangely enough, 2 days after the air admittance valve was replaced it suddenly appeared as though the sink was working again! It has been operating fine for the past week or so, sink drains off fine and when the dishwasher is on we don't get water coming up through the sink like we did before the issue appeared.

Tonight, the issue has come back again! Dishwasher on, waste water starting filling up the sink and drained off so slowly. We don't know what to do now, every plumber we call doesn't appear to have an idea and it seems the only option is fork out for CCTV surveys (so we've been told) which we can't really afford at the moment.

Does anyone have any ideas at all?

Our flat is in a house with 2 other flats, neither of which have issues.

Any help would be HUGELY appreciated!

 

[gassafe]

Difficult to say without knowing the set up of your flat & the length of run etc.. If everyone else is okay then it must be your run to the main stack... Look for any restriction in pipework or multiple bends etc where it could have accumulated...

Post up pics might help

 

[Billy Bob Bob]

sounds like its blocked elsewhere,probably a gully or in the sewer ,you can post up in our need a plumber section,someone should be able to sort the problem once and for all

 

[pwoakdon]

Thank you, I'll do that now!

 

[pwoakdon]

This morning I tried something that worked but it just makes the whole problem more baffling. I filled the sink up and took the plug out, the water just sat there as expected. I then put a screw driver into the air admittance valve and all of a sudden the water started to drain away. I can't believe that the valve has suddenly become faulty again after only 2 weeks so maybe it's something to do with the pressure or lack of it in the system? I have no idea but I hope someone does and can shed some light?

 

[rocketmanbkk]

Had it before, baffling, can't see any blockage, air, have you tried a wet vac & suck on waste? Sounds like air to me

 

[pwoakdon]

The first plumber tried a wet vac, it pulled out a few bits of waste but nothing huge, but didn't do much.

The first air admittance valve was glued on but the recently fitted second one can be unscrewed. I just removed it, filled the sink up and took the plug out - it seemed to drain off fine at first but then slowed right down and stopped completely for a while. Then it started draining again. Lots of gurgling and bubbling noises, still not right?

 

[rocketmanbkk]

Imo only I don't think it's blocked.

You could get it jetted but that sorts out blockages.

I'm still going the air route - anyone else?

 

[rocketmanbkk]

Is the Durgo above the flood level of sink?

 

[andyplumber2009]

what about not enough gap between the waste pipe and the top of the AAV?
If you remove the AAV is there still a problem?

If it was a full on waste blockage i would have thought you would have slow moving water in every sink as they would normally all join to a common soil stack

 

[andyplumber2009]

Sorry rocketman, just saw your replies

 

[rocketmanbkk]

Sorry rocketman, just saw your replies

No probs

 

[pwoakdon]

The AAV is at the same level as the plug hole in the sink, it was a few inches higher but the last plumber has to saw off the old one as it was glued on.

With the AAV completely removed the water is at least now draining although it seems to drain quickly then slow down then drain quickly etc. Also makes lots of gurgling noises which it never did before....

Any suggestions?

 

[rocketmanbkk]

Raise its height to above overflow level of sink

Which probably can't be done under sink unit!

 

[pwoakdon]

You're right, can't be done!

Might sound like a stupid question but would that make much of a difference?

Sounds like not a great deal can be done, shall I just leave the AAV off? I'm a bit worried that water might come up through the pipe and flood underneath the sink!

 

[rocketmanbkk]

Shouldn't do

Where do you live?

Might be a plumber on here who can help you

There's a 'I need a plumber' thread

You can maybe find someone there

 

[stevetheplumber]

youve answered your own problem the water is shutting the aav when you take the plug out raise it as high as you can under the wokrtop

 

[andyplumber2009]

Just to try to explain a bit about water... and gurgling
take a bottle of water and try to empty it by tipping up all at once and it glugs and gurgles and the air tries to get in to replace the water. it is trying to access the bottle through the same hole as the water is leaving. if you put a small pin hole in the bottle then the glug would ease (and be quiet). Put a large hole and the glug stops.
Your sink is the bottle, you are trying to put a large volume of water down a small hole. The AAV (Durgo) is letting air in and out easing the problem (making the gurgle quieter). Remove the AAV and the large hole lets you hear the gurgle.
This is positive, IMO it means that the water you are releasing down the sink is a large enough volume it is reaching the "neck of the bottle" further down the line. The water then stops flowing at this air blockage then slowly releases air into the pipe with it and starts to flow again.
I would find the route of your pipework. Does it flow out an external wall into a soil stack? or internal soil stack to a AAV fitted in the loft. Obviously i am guessing. Basically the problem is not air entering your sink waste but air not being able to be released further down the line

 

[rocketmanbkk]

Yep, I agree, it's air locking.

Durgo, gotta try to get it higher with the cap on as Steve said.

 

[Masood]

Just to try to explain a bit about water... and gurgling
take a bottle of water and try to empty it by tipping up all at once and it glugs and gurgles and the air tries to get in to replace the water. it is trying to access the bottle through the same hole as the water is leaving. if you put a small pin hole in the bottle then the glug would ease (and be quiet). Put a large hole and the glug stops.
Your sink is the bottle, you are trying to put a large volume of water down a small hole. The AAV (Durgo) is letting air in and out easing the problem (making the gurgle quieter). Remove the AAV and the large hole lets you hear the gurgle.
This is positive, IMO it means that the water you are releasing down the sink is a large enough volume it is reaching the "neck of the bottle" further down the line. The water then stops flowing at this air blockage then slowly releases air into the pipe with it and starts to flow again.
I would find the route of your pipework. Does it flow out an external wall into a soil stack? or internal soil stack to a AAV fitted in the loft. Obviously i am guessing. Basically the problem is not air entering your sink waste but air not being able to be released further down the line

However, this problem has only started recently. So the "bottleneck" isn't in the design or sizing of the pipework IMO. A partial blockage would cause a "plug" of water to form, and the subsequent vacuum/air bubble breaking, causing the flow -> stop -> gurgle -> flow bahaviour that the OP describes...

 

[rocketmanbkk]

Mmmmm....

 

[rocketmanbkk]

It's a difficult one, Durgo gotta be fixed, then jetted? One shot?

 

[Masood]

It's a difficult one, Durgo gotta be fixed, then jetted? One shot?

I'd follow the pipe run and see where there's a potential for trapped debris. I had an almost identical problem last week - they'd tried One Shot a couple of times, it worked a bit then blocked again - it was eating a hole through the blockage and running through, then it would block again. Found a lump of tissue and a mouse carcass in a T. Drain snake was curving up the other branch of the T, missing the blockage..

 

[rocketmanbkk]

Nasty.

Trouble is the OP can't afford to pay as they said so paying to investigate might be out.

Difficult situation

 

[stevetheplumber]

a lot customers say they cant pay but they always find it in the end once they are cold or wet enough

 

[Masood]

Nasty.

Trouble is the OP can't afford to pay as they said so paying to investigate might be out.

Difficult situation

True enough...

 

[pwoakdon]

Thanks for all your help so far, really very helpful. I've attached a picture of the pipe work under the sink so you can see, the AAV was attached to the top of the grey pipe at the back. As you can see I can't get it higher

If I run the tap the water drains absolutely fine now with the AAV removed, surely if there was a blockage of some sort the water would start to rise up? It only seems to be an issue now when the sink is filled up and the plug is taken out that it's very stop start....

Next door is on the opposite side of the wall so I'm guessing the pipe work runs underneath the flat and out the opposite side of the building

 

[plumben]

sounds to me like theres a possible blockage or partial blockage in the main stack either on the vent or the wet side

 

[stevetheplumber]

long run under floor will be full of crud ive had several like this usually dodgy flat conversions should have been run in 2 inch with a fall i bet if you lift a floor board this is just laying on the ceiling below

 

[Masood]

If I run the tap the water drains absolutely fine now with the AAV removed, surely if there was a blockage of some sort the water would start to rise up? It only seems to be an issue now when the sink is filled up and the plug is taken out that it's very stop start....

OK, this has already been explained, but one last time:

Imagine a bottle with a narrow-ish neck. Fill it water. Tip it slowly and water will run out nice and smoothly. That is the analogy of you turning the tap on. A steady stream that will run down the bottom of the waste pipe, with air above it, in a laminar flow.

Now imagine upending the bottle suddenly (filling the sink then pulling the plug). There will be "plug" of water, then it will stop, an air bubble will glug through the water, then there will be another plug of water, etc.

If the bottle neck is narrow, this will be more pronounced. A wider neck will be less so. Hence my suspicion that a partial blockage is causing enough of a narrowing to make this happen. When the pipe was totally clear (wider neck), it didn't happen.

By removing the AAV you've allowed a freer movement of air, improving the situation somewhat. Water would rise back up if the blockage were bigger. As it stands, it's allowing enough through to cause these plugs of water and the vacuum they create behind them.

As Steve said, the pipe is probably laying flat and has a layer of scum sitting on the bottom, narrowing the bore.