Shower trap emptying

[Barryscotland]

We have been moved in for 3 months now, starting from last week the shower trap has started emptying causing the on suite to stink. It’s a jackoboard linear drain and tray. Even when the house is empty for the day the trap empty’s so cant see it being sucked out and it can’t be evaporating that quick? Also when I’ve pulled the trap out to test it by filling it with water and checking for water leakage thinking it was maybe cracked (it holds water fine) I noticed what looks like a gap between shower tray waste and the cup on the end of the drainage pipe, is that normal or something that needs filled in? What else could cause trap to empty? 

[Onoff]

Do you have UHF, is that drying the trap out?

[Gus Potter]

@Barryscotland

 

Hi Barry.

 

If the trap is holding water then the seal is maintained. But you may be getting vacuum in the system. This often happens when you flush the toilet or use another sink say. The "plug" of water either fills the pipe to full or nearly full bore and that sucks the water out the shower trap as it creates a vacuum behind it and thus the smell comes out. These types of shower trap often have a very shallow water seal depth. 40 - 50mm as opposed to a kitchen sink washing machine trap with a 75mm water seal.

 

Look outside to see if you have a soil vent stack. Has the top come off and/or birds been nesting in this? Is it cranked and some bits have fallen off and it is now facing into the wind or on the leeward side say.

 

Next try first filling the shower trap. Then go around each sink/s and toilet/s one at a time. Use them in the way you have been doing and get someone to listen to the shower trap, or smell. Sounds weird but the first objective is to look for the simple stupid. Don't rush this, be patient.

 

Now some sinks have an anti syphon trap fitted. It may be that one of the anti syphon traps is sticky and not letting air into the drain to relieve the vacuum. The objective is to find the appliance or the thing that has changed in the system as it was working ok before.

 

Working up you may have a 110mm drain line that is like a branch line in the house. It may have a 110mm air admittance valve, a bigger animal than the small valve on say a sink trap. That may be sticky.

 

Try this and let us know how you get on.

 

 

 

 

 

 

 

 

[Barryscotland]

13 hours ago, Onoff said:

Do you have UHF, is that drying the trap out?

We do but it’s never been on but house is warm and trap only holds Half a ladle full so I’m thinking it must be evaporating as can’t be anything else. 

[Barryscotland]

13 hours ago, Gus Potter said:

@Barryscotland

 

 

There is an exterior vent after the shower and before it there is a toilet with an aav beside it so can’t see it being sooked away and it empty’s when the house is empty. House is warm so I’ve come to the conclusion it must be evaporating, I’ve removed the trap, filled it an left it sitting on the counter to see if it empty’s. It only took 100ml of water to fill the trap 

 

 

[saveasteading]

On 10/06/2022 at 22:44, Gus Potter said:

vacuum in the system.

My guess too.

Air has to enter from somewhere behind the draining water, and a shallow trap may offer least resistance.

[Rupe30]

Just wanted to jump in this post as I'm having the same problem and I have the exact same shower traps. I have no external soil pipe, but a durgo valve fitted inside, although it's been fitted in an inaccessible place. Whenever I flush a toilet I can see the water deplete from the traps and they hold such little water it's dry after a few flushes. Can a durgo valve be fitted incorrectly? Does it matter where the durgo valve is placed on a system? We have 3 shower traps, 3 toilets, 3 sinks & a bath running through this pipework. 

 

Thanks in advance!