Kitchen sink draining (air lock?)

[orap1]

Hi

I've been having some trouble with a kitchen sink draining slowly (from a full sink it seems to drain to half way ok then very slowly for the rest). We have also just had a new washing machine and when this drains it backs up a lot into the kitchen sink.

I thought it would be a blockage so I have cleaned the u-bend and used a rod to clean as much of the pipes as I can (a lot of gook came out but no obvious blockage).

Is it possible there is an air lock? and how would I fix this? I have also checked the overflow pipe isn't blocked and tried plunging a lot. Attached is a photo if this helps.

All help much appreciated

Thanks

Oliver

 

[Old Account]

In my opinion there must be a blockage further down the pipe work. Why would it back up if your waste is free ?
I am quite certain you will have a blockage further down the pipe work.

In this type of configuration plumbers sometimes oversize the waste line to make room for air to pass while water is flowing but If a partial blockage develops air flow is restricted and water flow slows down.

You could clear the blockage either plunging the sink but you need to do it while the water is backing up so that the pipes are full of water.

You will need to block those overflow holes & cap or shut off those washing machine drains.

Did you check your toilet is that still running fine ?