Shower & unvented cylinder installed in bathroom - all gone stinky !!

[muggles]

But doesn't a Tundish prevent this from happening as per the text below ? or do I need a different kind of Tundish ?

"The Tundish is a plastic cup which hooks on to the pressure relief valve. Its job is to catch the drips from the Pressure Relief Valve, and it is also a water trap to prevent any unpleasant odours escaping from the sink waste."

You need a different kind of description - that's wrong

 

[wwwebber]

Thanks all.

So, what needs to be done here exactly ?