users must empty the basin so that Shower can drain ?!?

[fallingditch]

When showering, users of my ensuite must fill the basin first, then turn on the shower; then pull the plug on the basin which causes the shower tray to then empty!

If they neglect this 'empty basin' step - the shower tray fills up - there is a very slight flow out of the tray but not as much as that coming in from the shower!

The shower tray is fitted with a typhoon vortex waste, emptying into 45mm waste pipe with a 3m run and a 35mm fall to the external wall, where it mates (hidden) with the basin outflow, and which then mates with the soil outflow from the toilet. Soil pipe then runs horizontally about 10m across external wall before mating with the soil stack.

(BTW have only lived here for 6 months ...)

 

[grrinc]

10m run??? hmmmm

I suspect an air admittance valve is in order. ( perhaps an AA trap can be fitted to the basin. ) This would be the simplist thing to try first.

Or positive pressure?? In which case the pipe will have to be opened and vented without AAV.