Shower drainage
Shower drain backs up until I turn on basin sink tap
Advice from 2 local tradespeople
It is very possible that shower and sink waste pipes connected together to one, what is not advisable. Every unit like sink, shower, bath, toilet and others should have its own separate waste pipes directed outside through the wall and connected downwards to the mane gully or connected to the 4 inch waste pipe directed downwards as well.
Now in this situation you might have peace of dirt standing stuck on a pipe joint and keeps moving about few mm in and out and preventing waste water from smooth let out.
This could be I variety of different issues but most commonly is caused be air holding in the pipe not allowing the shower to drain best thing to do is fit an AAV (Air admittance valve)
