Slow draining shower waste

[hammonchees]

Hi

There are many other threads on this but haven’t been able to find a solution so far. I have a fast-flow shower waste (in theory) in an ensuite shower, installed new about three years ago. All has been fine until recently so I don’t think this is a fundamental issue with the setup.

Lately the waste has been really slow to drain. If I remove the plastic cap (i.e. go from first to second image below) generally a large number of air bubbles come up and the water drains instantly. I don’t think there’s an issue with the pipework downstream of this waste, as the water continues to drain fine when this plastic cap is removed. There are two basins and a bath connected to the same pipe which runs externally and joins the main soil pipe just below the connections of two toilets. The basins and bath drain fine, although there is sometimes some gurgling from the bath drain when a toilet is flushed.

It’s as if a sort of vacuum/air lock is being created causing the slow drainage but not sure why all of a sudden. The external soil pipe vent seems to be fine as far as I can tell.

Any ideas appreciated! Many thanks.

 

[Hugh Jaleak]

I'd suspect a partial restriction downstream, preventing the water from flowing fast enough under gravity. When you remove the Dip Tube this effectively allow a siphonage effect to be created so it then sucks the water out of the tray.

I'd try putting a 'Snake' or other mechanical device suitable for cleaning waste pipes down there, and give it a good clean and see if that solves the issue. The fact it's happened after about 3 years would indicate a build up of soap, hair etc over time, not an inherent issue with the pipework.

 

[screamer]

would an anti syphon basin trap help? would maybe help with the gurgling sounds coming from the basin/bath

 

[hammonchees]

Thanks for your replies!

I’ve only tried using chemical unblockers in the past so will buy a snake and give that a go. Cheers.