Wash basin void fills with water?!?

[dogfonos]

OK, not exactly a disaster but it's weird...

I clean my wash basin and bath drains by periodically blasting mains pressure water (via a hose) down the plugholes. Very quick, no chemicals and it does a great job. Done it a good few times and if careful, doesn't spray water around the bathroom.

Last week, I thought the wash basin drain looked grubby so I gave that a blast too. After a few seconds, water began to run out of a small drain hole on the underside of the basin! WTF? Turns out that the basin overflow must somehow/somewhere be open to the ceramic washbasin void, i.e. the air space between inner and outer basin surfaces, and I had managed to fill (well, up to the level of the void drain hole - so about half fill) the void space with water.

Obviously, I couldn't leave the water as it will soon 'go off' and cause odours. So, I carefully threaded a thin plastic tube through the small void drain hole and teased it into the area beneath the bowl (did it by feel as I couldn't see a thing). When I thought the tube was in place, I blew into it and heard bubbling water - proof that water now part filled the void. I managed to get a siphon going and removed over a litre of water. I think I had emptied the void but small amounts of water may have remained so I borrowed a pond aerator pump and set that up to blow air into the void for a few days. Nearly a week has passed and no odours as yet. Fingers crossed it stays that way.

 

[Bonni]

Sinks come in two types, solid and hollow. So there are two types of waste fittings that screw into the sink. D you have the correct one fitted?

 

[dogfonos]

Sinks come in two types, solid and hollow. So there are two types of waste fittings that screw into the sink. D you have the correct one fitted?

Something to bear in mind when I refurb the bathroom.

The current wash basin is definitely pre-1990 - I suspect it's a late 70's design. The plughole drain fittings don't seem to be the problem as I've blasted water down the plughole many times without the basin hollow filling up so I think the drain fittings are fine. Besides, if the basin hollow was somehow opened to the drain pipe just below the plughole, then any water collecting in the hollow should drain out, I think.

The basin has an integrated ceramic overflow that's part of the basin's moulding so it's not user configurable. The ceramic overflow connects to the basin drain pipe just below the plughole and before the U-bend.

It seems the overflow is open/vented to the basin's hollow space at the overflow's uppermost point, i.e. above 'normal' overflow water level. This may be done to prevent air locks when the basin overflows as the hollow space has a small drain/vent hole to the room. Who'd have thought it (not me, obviously)?

 

[opps]

As per Bonni's post, a sink with an overflow has a waste that has a slot in it to allow the overflow water to run in to the waste pipe. It sounds like someone has fitted an unslotted waste fitting. The water from the waste pipe cannot go anywhere other than run down the big nut.

See

https://knowhow.sparespro.co.uk/slotted-or-unslotted-basin-waste/

The slot should line up with the outlet for the overflow.

 

[lostinthelight]

Aside from Op’s problem, the seal above the big nut should be forming a seal between either the basin, overflow boss and threads anyway so if fitted correctly no water should escape

 

[opps]

Aside from Op’s problem, the seal above the big nut should be forming a seal between either the basin, overflow boss and threads anyway so if fitted correctly no water should escape

Point taken but if the previous person wasn't savvy enough to fit the correct fitting, it is likely that they wouldn't have fitted the incorrect fitting correctly.

 

[opps]

Aside from Op’s problem, the seal above the big nut should be forming a seal between either the basin, overflow boss and threads anyway so if fitted correctly no water should escape

Oh, and it should be noted that without a slot, the overflow, won't function as an overflow.

 

[lostinthelight]

Oh, and it should be noted that without a slot, the overflow, won't function as an overflow.

Obvious to those that know, Perhaps better directed towards the Op?

 

[opps]

Obvious to those that know, Perhaps better directed towards the Op?

Sorry, yes, point taken. It was a clumsy way of trying to let the op know that what they have is wrong.

 

[JohnD]

I have a cloakroom basin, with a slotted waste, and water from the overflow drips out of the vent holes under the basin. Professionally fitted by an experienced plumber.

Might the waste be incorrectly fitted? How can I check?