Hi, My kitchen sink, well to be percise is not blocked but the water goes nowhere. I can only guess that this must be a pressure issue. The ptrap is on fine but the water won't go around it. I also have a pipe coming in at the top for the washing machine waste but I don't understand how this would affect it. I don't know what has changed on the whole set up. Any help would be great.

Sounds like you may have a partial clog in the horizontal drain in the wall. The solution would be to remove the traps "J" bend and send a snake up into the wall,(see image). There's a bend ablout 8 inches in but once around that you only have to put out 6 more feet of snake. Flush with a tub of hot water. Good luck and thank you for ratting my answer. Tom

Thanks tom but I don't think the waste to the wall is the issue as when I had a previous ptrap it worked sometimes. The pipe to the wall is wide and looks clean. Thanks for your help

Is your sink vented? And I would be interested in just how you can tell that the drain line inside the wall isn't clogged. Regards, Tom

Tom, I don't believe the waste in the wall is blocked as when I undo the Ptrap and clear it out, I then refit everything and turn on the water. The water does not have enough time to fill or get to the wall before it starts blocking up again, Its as if it is just filling up the ubend in the ptrap and then filing up to the base of the sink. Not to sure what you mean by vented. Below the sink is the connection to tne sink, i.e. the overflow, below that is the tube in for the washing machine then it goes down into the ubend and down a approx 1 and a half inch waste to the wall.