Waste from Shower & Basin (& Bath)

[CHarr]

I'm about to do the waste pipes in my new bathroom. The 40mm waste pipe passes out of an external wall to the main stack and there is a 2.5m run to the shower trap. I need to cut into that, mid-way, to connect a basin. I was looking at a Floplast Anti-Vac bottle trap - is that suitable for the basin?

I also need to connect the bath outlet, but it comes from the other side of where the waste pipe passes out of the wall. Would I be better to have a completely separate 40mm pipe going into a different boss on the main stack, or is there a fitting that would allow me to merge two 40mm pipes (coming from opposite directions) into one going out at 90 degrees. A swept tee is the right shape, but I can't imagine the flow would be very good from the side going the 'wrong way'...

 

[Madrab]

Yes an anti-vac bottle trap is fine for the basin but I always recommend McAlpine, so well made and never had an issue with them leaking, worth the extra couple of quid.
A swept T must be used in the correct direction otherwise it will cause turbulence and flow incorrectly. I would run a separate waste for the bath as joining two waists in a T like that you could get backflow up one when the other is drained. Either that or join the bath further down the run going outside to the stack

 

[Hugh Jaleak]

Second Rob's advice. Bath and shower on same waste can cause issues, seen contents of bath reappear in the shower on several occasions, and in one case, flood the bathroom after bather had pulled the plug from the bath and gone next door to bedroom. Waste had near enough blocked so water found it's own level exiting via the shower tray.....

 

[longdogs]

If you really have to connect the shower and bath to the same waste pipe then fit a 40mm non-return valve on the shower waste. These have to be fitted in the correct direction of flow and the right way up.