Hello,

Has anyone tried the anti-siphon traps from Screwfix and do they work?

In our bathroom, the builders joined the basin and bath waste with a
tee, so when the bath empties the basin "burps".

I know two separate wastes would fix this but in their wisdom the
builders hid the soil stack in the wall and I would have to take half
the bathroom and half the kitchen apart to get to it!

I have fitted such a trap to the basin but it still burps!

From the outside it looks like a normal trap. How is it supposed to
work?

Thanks,