Backing up sink - air-lock? blocked manhole? Help!!

[epymsam]

My kitchen sink is gurgling and backing up when large volumes of water are put down it. The washing machine drain is plumbed above the u-bend and when it drains it fills up back into the sink.

I've had dyno-rod over, disassembled the under-sink drainage and its all clear. The chap cleared the pipe from the small standpipe under the sink as far as he could go, with no problems i.e. no blocking there.

We tried the drain by putting a hose down the smal stand pipe and we could let it run for ages with no backing-up at all.

I noticed that when the sink is backed up, if I pull the flexible drain house out of the standpipe a little, air rushes out and the sink clears instantly. It seems to be some kind of air-lock.

What can I do, is it a drain venting problem? Could it be a problem with the soil stack, which I guess it where the drain is vented?

I was considering trying to lift the manhole cover to see if that was full, but unfortunately this is under the kitchen floor, as an extension has been built over it!! Could a blocked manhole cause this problem?

Eventually the sink does drain away, but it is very slow. I'm racking my brains to try to think what coud be causing the problem. We've been in the house for over two years with no problems.

 

[gas4you]

Does the sink empty ok if you leave the w/m drain pipe out all the time?

 

[epymsam]

I'll have to try that, w/m on at the moment so will have to try later. Could that be the cause? If so what's going on?

 

[epymsam]

Just to clarify, the flexible pipe that I remove from the standpipe make the final connection to to the standpipe which runs underground - I assume straight to the manhole. Its not removing the flexible w/m drain hose which lets the sink clear.

 

[gas4you]

I'm not really understanding your drain set up.

What is this standpipe if it is not a w/m standpipe kit that the w/m drain outlet pushes into?

What is this fleaxible drain pipe? Do you mean the overflow from the sink to the waste underneath?

I take it you mean that the w/m drain is pushed onto a spigot which is built into the sink waste/trap?

 

[noseall]

the inspection chamber has been concreted over

 

[epymsam]

Dave,

The sink set up is a follows:

Waste from under sink has two further attachments.
a flexible hose fom the overflow to the sink
a flexible hose from the w/m waste connected onto a spigot.

the waste then runs into a u-bend and then onto a similar diamater short length of flexible hose which connects directly into a plastic stand-pipe which runs under the ground into what I can only assume is the manhole.

Its whn I remove the finsl piece of flexible pipe from the standpipe that the skink flushes away clear.

Noseall, yes it does appear that the main inspection cover has been concreted over. I removed a tile form the floor today and it seems that the foundations have been laid directly over the top. There is a rodding point outside though which seems to be the only route into the inspection cover save for digging up the kitchen floor!!!

Any ideas why I might be getting the problem?

 

[gas4you]

Perhaps fitting an air admittance valve to the waste under the sink would cure it. This would release any vaccuum that would be present when the sink tries to empty.

 

[Softus]

the inspection chamber has been concreted over

I had one of those on Saturday. Wanna see the before and after?

 

[noseall]

looks much better now the cobwebs have gone.

 

[epymsam]

So, if my manhole is nicely placed under the floor of my extension (I knew I should have had that drainage survey done when we bought the house two and a half years ago) how simple would it be to build a new manhole? Would the existing manhole need to be diverted / pipes altered or can another one be constructed and connected up to the existing one?

Any ideas on price? Also, if I cant practically get through the kitchen floor, is it possible to intercept the outlet of the exiting manhole as it runs to the main sever and access through there to clear any blockage?

This smells expensive!

Thanks for all your help by the way.

 

[ms90]

I am experiencing exactly the same issue! Did you get a solution?

We have the same flexible hose going to the stand pipe, and the same rush of air when I slowly ease it out as the sink drains. Air rushes in/out (?) and the sink drains. Mind I need to connect it back quickly before the water starts pouring out!

I think this is IKEA plumbing, but not sure.

Any advice appreciated.

Cheers,

Martin.

 

[andytheplumber]

siphonic action. to much water in to smaller pipe. Either increase the pipe sizes, or add an air addmitance valve, or both

 

[Softus]

Any advice appreciated.

My advise is to start a new topic.