Great device
The HepVO is a "dry trap", so doesn't dry out if not used for a while. These have solved problems of odour in a bathroom that's not used often (where the traps dry out) and I've also got one on the drain connection to my boiler over-pressure valve. They also act as an air admittance valve, are really small and fast flowing. I've used 6 of these now and the quality is very good.
They don't block sound in the way a conventional trap would, so you can hear some gurgling from other parts of the house, and they won't hold items you drop down the sink in the way a conventional trap will.
Verified purchase: YesCondition: New