My 65mm shower drain is connected to the 100mm toilet out-flow below the toilet u-bend below the first floor bathroom (I live in Holland by-the way).
When the toilet flushes the fouls tend to cause a vacuum at the shower u-bend which allows the foul smells from the public drain to percolate into the bathroom.
I had thought of making an extra u-bend in the toilet drain to slow down the "slug" effect but the toilet drian is cased and therefore inaccessible
Any ideas as to how to maintain a water barrier to the shower drain?

Brian Hedley, January 2005

you need an air admitance valve fitted between the toilet pipe and your shower trap

ian, June 2008

Thnaks Luke, I will make some enquiries locally to see if this is available.

Brian Hedley, January 2005

Syphoning action is a pain.
You need an air admitance valve but it must be fitted internally and vertical.
GO TO www.wavin.co.uk
This is the Osma web site
Select
Technical tool box on the top line.
Then Installation guide from the list.

Then select the following in order from each displayed list.

Above Ground Drainage
Waste & Traps
Osma Push-Fit Waste Installation Guide
OsmaVent 40 Air Admittance Valve

This shows diagram and installation instructions
you may be able to obtain the same thing in Holland
This fits 32 & 40mm pipe so you will have to adapt this by inserting a 'strap boss' in the existing pipe work which might be easier than fitting a Tee piece. I assume the existing pipe is plastic as you need to cut a hole for the inner part of the boss to fit in and seal it off with plastic pipe cement [It's similar to the plastic modeling cement]


If you are able to fit one of these then it should stop the syphoning action of the wc and eleminate the drain odour.
If you have problems accessing the site drop me an email via lukesmith8@hotmail.co.uk and I will try sending an attachment of diagram and installation instructions.

Luke, January 2005