Mysterious slow draining sink

[KenB]

Hi, I have a mysterious problem I have been banging my head against for the last year. I hope somebody might be able to make a suggestion as to what the problem is.

In my upstairs bathroom I have a toilet, a shower, a bath and a sink. Looking from the outside I can see that the toilet has its own waste pipe, and that there is only one other waste pipe. Presumably therefore the bath, shower and sink wastes are connected before going through the wall. The small waste pipe feeds into the toilet waste pipe some ten inches down the wall on the outside.

The bath and the shower drain very well with no problems. The sink on the other hand drains painfully slowly.

To investigate the sink drainage I have:

+ Repeatedly plunged the sink. This can make the water in the sink while plunging drain out quickly, but the problem returns with the next sink full.

+ Poured down all manner of caustic chemicals. This makes no difference.

+ Dismantled the U-bend – which was completely free from sludge, and allowed me to look through the plug hole clearly at the floor below.

+ With the U-bend removed I have run a hose down the waste pipe on full for several minutes and the water has disappeared quickly with no backlog at all (so I can only assume the pipe is clear).

Strangely the problem seems worse if you have just flushed the toilet, but I cannot see how this could be.

The sink would seem to defy gravity. Any ideas? Thanks!
Ken.

 

[ChrisR]

How slow is slow?

Has it changed at all?
What type of trap does it have? (many on view at bes.ltd.uk)
What size plug hole/trap is it; nominally should be 32mm, but some are only 25?
Any gurgling at shower or bath when one of the other wastes is used?
TRy draining the basin (it isn't a sink, they're different!!) while the bath is emptying - any slower?

 

[KenB]

>How slow is slow?

Verrrrry slow. To slow to bother waiting for it to drain after you have rinsed your toothbrush. I'm getting a lot of grief from my good lady.

>Has it changed at all?
When we first moved in it seemed fine for the first 4 or 5 months. Then it started.

>What type of trap does it have? (many on view at bes.ltd.uk)
Looks most like the 'P', third down on their page of traps.

>What size plug hole/trap is it; nominally should be 32mm, but some are only 25?

The plug measures at 32mm diameter.

>Any gurgling at shower or bath when one of the other wastes is used?

Using the shower can make the bath gurgle, and visa versa. The 'basin' does not seem to make either gurgle unless I'm plundging, but this is probably as its too slow.

>TRy draining the basin (it isn't a sink, they're different!!) while the bath is emptying - any slower?

Well its definately not faster. Difficult to say if its any slower.


One other thing I didn't mention in my original email is the sound it makes when draining. If you listen at the down pipe you can hear the water just slowly trickle away. There is a distinct trickle sound, so the pipe cannot be full of water?

I appreciate you taking the time to reply. Out of interest, what is a sink then?

Regards.

 

[Beans-on-Toast]

A sink is where you wash your dishes.......

 

[Bahco]

Is your soil pipe vented? Could be blocked at the top not allowing air in to assist drainage.
I would change your basin trap for a anti vac one first. These allow air in which should solve your problem if there is no blockage.

 

[KenB]

Much obliged.

 

[Plumbangel123]

I too had a similar problem with a sink that overflowed regularly as it took so long to drain. Tried everything until I bought a blockblaster plunger from a home show. They said it was brilliant for unexplained slow drainage. It uses a CO2 gas (like what you use for fizzy drink machines). You cover the overflow and whilst there is water in the sink, blast away. It cured it instantly. It also has different attachments for toilets and showers/baths too so its great for the whole house. I am now constantly being asked to take it to my friends houses to sort all their plumb issues out, hence my name!!

 

[Homesafe]

I too had a similar problem with a sink that overflowed regularly as it took so long to drain. Tried everything until I bought a blockblaster plunger from a home show. They said it was brilliant for unexplained slow drainage. It uses a CO2 gas (like what you use for fizzy drink machines). You cover the overflow and whilst there is water in the sink, blast away. It cured it instantly. It also has different attachments for toilets and showers/baths too so its great for the whole house. I am now constantly being asked to take it to my friends houses to sort all their plumb issues out, hence my name!!

I cant recall the name of the plunger youve got, but Be carefull, they have quite a blast and can in some cases blow a joint out, usually the pushfit type.
Your friends will have a nice and cleared basin though

 

[Plumbangel123]

I too had a similar problem with a sink that overflowed regularly as it took so long to drain. Tried everything until I bought a blockblaster plunger from a home show. They said it was brilliant for unexplained slow drainage. It uses a CO2 gas (like what you use for fizzy drink machines). You cover the overflow and whilst there is water in the sink, blast away. It cured it instantly. It also has different attachments for toilets and showers/baths too so its great for the whole house. I am now constantly being asked to take it to my friends houses to sort all their plumb issues out, hence my name!!

I cant recall the name of the plunger youve got, but Be carefull, they have quite a blast and can in some cases blow a joint out, usually the pushfit type.
Your friends will have a nice and cleared basin though

Yes it is powerful, but have heard that when you use the air pump ones you can over blast and damage pipes. This is CO2 and has been designed to project a powerful yet safe amount. I guess if you have poor pipe work in the first place anything you do can cause damage even nasty acids.