DIY Doctor UK DIY Forums

I am hoping someone can help ... our kitchen sink stopped draining, it looks like an airlock somewhere. This is what I tried:

1) Used chemical drain unblocked and plunger
2) Took everything apart and checked all pipes
3) Bought endoscope and inspected all pipes all the way to 110 soil pipe - all clean
4) Replaced bottle trap (McAlpine C10V Anti-Vac). Also tried McAlpine S Trap
5) When the sink is full and not draining, I can push the AAV up with my finger, then the valve starts sucking air in and the sink starts draining. This is why I suspect the issue is with the airlock somewhere

This is our current plumbing, many thanks:

Hi borisuk2000,
If lifting the AAV allows the sink to drain there must be a blockage further downstream - you’ve just got to locate it.
Regards S

So it turned out that the issue was with the very badly blocked soil pipe.

I bought Karcher drain cleaner which worked perfectly. Soil pipe is clean now and the sink drains like never before. It took about 3 hours to clean 15m of very badly blocked 110mm soil pipe.