Do I need an anti-syphon trap,or is there a better solution?

[slippyr4]

Hi All,

My bathroom has a washbasin and bath. The basin is a half-pedestal one with a standard U bend trap, which goes out of the wall in 32mm.

Outside, the 32mm pipe has an elbox, then proceeds diagonally down to the bath waste exist, which is a 40mm tee - one side has a 32->40 adaptor. the centre of the Tee conencts to the bath trap, and the other side of the tee proceeds along the wall for another metre before it ends above a hopper.

The problem is that when you empty the bath, it sucks the water out of the basin trap and it makes a lot of noise!

what is the proper solution to this? I understand I could fit an anti-syphon trap to the basin, but is there a better solution? the anti-syphon trap seems to me like it's a bodge to fix a fundamentally flawed installaition, so how should it have been set up?

thanks

slip

 

[seco services]

Nothing wrong with an anti-syphon trap
or keep the two waste pipes seperate.

 

[Charnwood]

the anti-syphon trap seems to me like it's a bodge

Anti-syphon traps are made for exactly your situation, to stop traps emptying by stopping the syphonic action, hence anti-syphon.