Kitchen Sink - Bad waste pipe installation?

[FunkyCowie]

I have been told that the waste pipe installation in my flat has been done incorrectly by a plumber 'friend' who said that if I installed an air admittance valve it should correct the air lock that has been happening.

The set up was installed by a kitchen fitter and was sort of ok for 1 year with on and off issues. I thought they were blockages as a plunger seemed to clear it for a while but the washing machine began to back wash due to something.

As described in the picture above there is about a 3m run of 40mm pipe (D) leading to a 90 degree angle and a further 1m run of 40mm pipe (C) before the trap.

A: Position of air admittance valve (AAV) that didn't alleviate the problem
B: Spigot from washing machine with non return valve.

Before putting the AAV in place I managed to get the water to run fine just by removing the washing machine and leaving the spigot open. So installed the AAV, the water then backed up and came out of the AAV.

I also tried an AAV that sat near to the top of the sink from a tee inserted where the old AAV was, still the same but no leak.

I have had an auger all the way into the wall with no signs of blockage.

Does any one have an idea where I should go from here without having to get my kitchen completely redone?


Thanks!


PS Should the AAV be half way along the long run of 40mm pipe or should that run have been 2' (50mm pipe)?

 

[gasbanni]

Where does the end of the waste pipe go ? through an external wall and in to a gulley ?

It looks like you just need a fall on it as it appears to be run horizontally, bit hard to give a definitive answer without seeing or knowing the full details of the installation.

 

[FunkyCowie]

I live in a block of mostly ex-council flats on the 9th floor, the 3m run goes into the wall that adjoins the bathroom but behind it so I can only guess it heads into an internal communal soil/waste pipe. People above and below do not have the same problem as me. I do not know what their set ups are.

There is a slight downward slope along the whole run from (A) to where (D) hits the wall... after that I'd need x-ray vision as the council seem clueless about the the plans for the building.

Thanks for responding.

 

[moggridgeplumbing]

The long pipe run should have been upgraded to 2" but in reality it is not often done.

The problem is you do have a blockage along the run somewhere, or the run has such a slow fall the discharge is running full bore. Or more commonly seen the long pipe run is not properly clipped which lets the pipe sag thus causing a dip for muck and water to accumulate. So even providing an AAV the problem will still exist.

Check all of these possible causes. Also does it run into an external gulley or stack or internal stack?

 

[FunkyCowie]

internal stack and I have had an auger in a few feet into the wall and the only resistance I met was from corners.

thanks for responding.

 

[HERTS P&D]

You could always do a service wash on the washing machine, which is put the machine on its hottest wash (90 degrees) and let it run full cycle with no clothes or any powder in the draw.

This should be done once a month on all washing machines as its good for the machine and good for the pipe work.

Giving away trade secrets every day.

Andy