Sink won't drain but there's no blockage?

[Londoner]

Plumbing newbie here (if you couldn't tell)...

Our sink suddenly stopped draining tonight so I tried the old plunger. No luck. Quite a lot of resistance with water coming back up the overflow etc.

No unblocker to hand, so I dismantled the undersink pipes. The weird thing is, there was some gunk but no major blockage as far as I could tell. Tried tunning water through it and also the back pipe - flow seemed OK.

One rubber washer is broken, which is causing a trickling leak so I'll replace that. But can that alone cause a sink not to drain? My elementary physics tells me there must be something else??

Any help appreciated.

 

[Slugbabydotcom]

A its blocked
B it isnt

You had A and now you have B
When it goes back to A and you have a problem give us a shout

 

[Nige F]

There could`ve been a "slug" of fat further down the pipework quite likely trapped on one of those tightt bends

 

[Londoner]

OK this is bizarre. Have replaced washer. No leak any more. Good.

I've taken the pipes apart: Water flows down the main waste pipe at the back - no major blockage

Water flows through the individual bits of pipe - they're dirty but there's no major blockage.

Water flows from the plug hole directly down - no major blockage.

But when I reassemble everything, water absolutely does not drain. it trickes away as if the pipe was almost completely bunged up!

I must be something wrong/missing something here but what??? I'm stumped here.

 

[Bathfitter]

can you provide a picture. Is this drain going through a disposal? When you put it back together did a little water go down then stop?

 

[Londoner]

When I put it back together and turned on the tap, the amount of water the went down the plug hole was roughly the capacity of the u-bend and pipes, then the sink started filling. No disposal - this is just a standard kitchen sink.

i guess this has all the signs of something blocking the pipe but I don't understand why I couldn't find it and why water seems to flow reasonably OK through each individual part when tested.

I have emptied a bottle of domestic sink unblocker and will leave it overnight. I guess there's a chance that there is still something clinging to the sides.

Other than that, I can't think what it could be! Most strange...

 

[Londoner]

Well the damn thing is still blocked this morning. I guess it's dismantling time yet again.

 

[Bahco]

The laws of physics say that it has to drain away if there is no blockage.
Does your waste pipe have a fall on it?

Does it drain into a gulley or straight into a soil pipe?

Disconnect the lot including trap and investigate.

 

[jas05]

remove sink trap
then connect a hose from cold tap,
push the hose into the wastepipe
wrap a cloth round
hold firmly
slowly open the cold tap
should clear..........

 

[Londoner]

Thanks for the tips but I am certain now that there is no physical blockage.

I've dismantled the pipes, used a drain unblocking tool and fed water through all the seperate bits of pipe and water flows fine through them all. I have emptied a 2ltr bottle of water right into the back waste pipe too and it drains without any problem.

But as SOON as i reconnect everything the sink fails to drain and the effect is so extreme that it seems like the pipe is totally bunged up - which I know it isn't. It's bizarre!

And as you'd expect, when we use the washing machine the waste water splurges up into the sink almost immediately. Everything was working ok until these last few days (although a small amount of water did used to come up into the sink when the washing machine was running, and then drain away).

Could there is some kind of weird siphon effect going on. Can this happen? And 'out of the blue' too?

More details: OK so working down from the plughole we have the rubber seal and the overflow assembly. Below that is a piece of pipe with the washing machine waste pipe entering it in the form of a t-junction. Below that is the U bend. Then there is a horizontal bit of pipe which then leads to a vertical pipe which leads to a horizontal pipe and carries the water out of the kitchen (that's as far as I've gone).


Like I said, I've tested each and every stage of the piping seperately and there is nothign stopping water flowing. The problem only arises when I reassemble everything and 'close the system' as it were.

 

[Nige F]

Thanks for the tips but I am certain now that there is no physical blockage.

a horizontal pipe and carries the water out of the kitchen (that's as far as I've gone).

Then go a bit further If it aint a physical blockage it`s a bleedin Ghost blockage

 

[Londoner]

There can't be a blockage even further down because I have literally poured water into the pipe and it has flowed away quite happily. That's what I don't understand!

I should also add that we are in a 3rd (top) floor flat.

 

[Softus]

There can't be a blockage even further down because I have literally poured water into the pipe and it has flowed away quite happily.

Something funny going on here. Are you saying that you can remove the topmost nut (from the washing m/c adaptor to the waste), and pour water down it and it flows away, and yet when you connect it back up to the sink waste then it's blocked?

If so, then either you have the plug in the sink or you're winding us up.

 

[Londoner]

There can't be a blockage even further down because I have literally poured water into the pipe and it has flowed away quite happily.

Something funny going on here. Are you saying that you can remove the topmost nut (from the washing m/c adaptor to the waste), and pour water down it and it flows away, and yet when you connect it back up to the sink waste then it's blocked?

If so, then either you have the plug in the sink or you're winding us up.

I haven't taken off the t-juntion part specifically but I have poured water down it, into a bucket. I've also poured water through every other part of the pipework in the pic.

What seems to be happening is at the very point I reassmeble everything, something is happening that blocks the flow. It seems to be related to the doing up of the joints.

I don't blame you for thinking this is a wind-up because right now I feel like the sink is winding me up!

Anyway a call to a professional beckons and I will leave them to figure it out, because I sure as heck can't!

 

[trickiedickiedido]

I have a very similar problem. My S bend behind the washing machine is trapping water. Like this post, I've removed every bit of pipe work (even removed the kitchen units to do this!) and cannot find ANY sort of blockage. Basically the grey hose from the washing machine goes into a long vertical pipe then into the s bend. The water will go through but after a few seconds the vertical pipe fills up and over flows. This is driving me nuts. I am quite handy at DIY and this has me stumped. I begrudge calling in an expert who will charge me around £50 to point out something obvious! PLEASE HELP! Failing a result here I think I'll call in the local priest.

Ricahrd