Bottle trap smell

[dave7108]

I have a bottle trap under the cloakroom sink but it seems to let in smells from the sewer. Do bottle traps like this keep smells out or do i need a traditional U bend trap?

[Jonny_]

Is it the sewer or the trap itself?

Drain plumbing and traps can get very smelly if gunk has built up over the years.

Chemical drain cleaner might do the job. But failing that it's worth taking the trap to bits and giving it a proper clean.

Unless the trap is internally damaged, it should maintain a water seal against any gases entering from the sewer system. This is what all traps are designed to do whether it's a U bend, P trap, bottle trap etc.

[paulwirral]

How often is it used ? If not used regularly run the tap now and again , my downstairs bathroom does the same in the basin and shower as it’s rarely used .

[dave7108]

The trap and sink are new about 4 weeks old. When i put the plug in the smell seems to go.
Thanks

[JoshSm]

Probably over extended the adjustment on it so the pipe down from the basin isn't exiting below the level of the trap outlet?

Traps are simple things but looking at it that particular one lets you fk up the installation.

[Panamax]

If a foul drain system is not properly vented you can find a trap gets emptied. When a toilet is flushed a surge of water goes down the drain system pushing high pressure in front of it and causing reduced pressure behind it. That reduced pressure can easily suck the water down and out of a sink trap and in extremes cases can suck the water out of a toilet u-bend - if the system isn't open to atmosphere.

I would start by removing the bottle trap and see what's going on inside. It's a good idea to clear them out from time to time and if it's the trap that's partially blocked and stinks then you've solved your problem. If the trap looks good and clear then just reassemble it and run some water to make sure it's filled.

Over the following days see if any smell develops and keep running the tap from time to time to maintain water in the trap. After that period and assuming no smell develops, leave the basin unused for several days. If the place starts to sink then it may be the trap has been emptied. Remove the trap again and see if there's any water in it.

If there's no water in the trap you need to see if there's a blockage somewhere else or whether an air vent has been obstructed. Something would be causing pressure variation in your foul drains.

[GasEngineer]

JoshSm said:

Probably over extended the adjustment on it so the pipe down from the basin isn't exiting below the level of the trap outlet?

Traps are simple things but looking at it that particular one lets you fk up the installation.

I don't think that is the case with this type of trap. It has a plastic insert that acts as the air break. You can have the top pipe fully extended.

[shtu]

GasEngineer said:

this type of trap... has a plastic insert that acts as the air break

Worth checking that plastic tube is still there and in place.

[fooman]

If it's new there's either a problem with installation or the water is being sucked out of the trap, there's valves you can add at either the trap or further down waste to help.