Blocked Kitchen sink nightmare!

[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.