DIY Doctor UK DIY Forums

Hi.

We have a holiday cottage that has 2 bedrooms with ensuite wet room style showers, wash basin & wc, and an open plan lounge and dining kitchen area.

Our problem is that when the wash basins or the sink in the kitchen drain water, they create a vacuum and suck the water out of the shower water traps. This allows foul smells back up into the shower.

A builder has told us that we need to separate completely our bedroom and kitchen basins from our showers that would involve a lot of new plumbing. Another plumber has suggested that if we install anti vac traps on the water basins that this might solve it.

I’d really welcome some advice as a novice in the plumbing world!

I attach two pictures that show the type of shower water traps that we have.

Anthony

Anthony, a few thoughts;

Is it both basins that cause the trap to be pulled out?

Shower trap will be very shallow and difficult to replace /alter.

Anti vac traps to the whb's will only prevent the traps to those basins being pulled. Fitting an anti vac trap to the shower will stop this being pulled.

Can you fit an air admittance valve (aav) between the whb's and the shower at some point. This could be a small 50mm aav but when the whb's are drained, air will be drawn into the system through the aav rather than sucking the shower trap out.

hth,

xavi

Dear Xavi,

Mant thanks for your help on this one. So, do you mean that fitting anti-vac traps on the sinks won't stop the shower water traps being pulled? All that is on the pipe is 2 shower and basin traps, a kitchen basin & a dish washer. Also the smell we get only seems to impact one of the shower traps so I think only one of them is being pulled out completely.

Best regards, Anthony

Dear Anthony,

My understanding is that an anti vac trap only prevents to the trap being pulled on the trap that it is fitted to.

However, perhaps you could google anti vac trap, find a manufacturer and ask their tech dept. I've always found most manufacturers tech depts to be very helpful.

Good luck,

xavi

Dear Xavi,

Many thanks for your advice - I'll give an enquiry to a tech dept a go.

Best regards, Anthony

Dear Xavi,

Just to say a big thank you for your advice. We have had 3 air admittance valves fitted and it has solved the problem. The water is no longer sucked out of the shower traps & hence there is no smell. Brilliant. Many thanks.

Best regards, Anthony

I've just come across this post.

haoconn - thanks for coming back and informing us that this solved the problem, this will help others with similar issues.

You tend to get many asking for advice but they very rarely give feedback on if it worked, we can only assume it did and that's why they've never come back.

Hello Anthony,
if by any chance you're still following this forum, I have the same exact problem with my shower. I was already planning to install an air admittance valve (that's how I found this page, while searching about that).
I would be curious to know where/how you have installed your 3 air admittance valves that resolves the issue, I mean in which spot, as you haven't provided any details about that. If possible, thanks!!!
Michal

Hi Michal,
Re your question, we fitted 3 valves to the 2 bathroom sinks and the kitchen sink. Please see pic.
Good luck, Anthony

Thanks, my plumber has also advised to place the valves under the sinks, but I was concerned if that would fix the shower smell. Meaning if those sinks valves would help release vacuum from the shower traps. From your answer it seems it could work. Thank you so much!