@Super_Paulie  Where did you get  this connector ?

 

I have only seen double ones with an air admittance valve to go on the top of a standpipe.

I think it was this.

Thanks greatly @Super_Paulie 

So you don't need an air admittance valve when doing that then ?

And I notice you still kept a standpipe like height above the u bend.

6 minutes ago, Spinny said:

Thanks greatly @Super_Paulie 

So you don't need an air admittance valve when doing that then ?

And I notice you still kept a standpipe like height above the u bend.

 

Each appliance is on its own waste so no AAV. Standpipe just to create the traps.

So if my toilet basin with it's bottle trap is plumbed to connect into the same 40mm slight horizontal fall waste pipe that my washing machine discharges through do I need to fit an air admittance valve ?

Id imagine the would make the trap in the basin gurgle as it creates a vacuum when the machine discharges and will pull water from the basin bottle. 

 

Change the bottle for a trap with an AAV built in? Or whack in a 40mm branch with the AAV on one side?