ISTR this has cropped up before but G groups was unhelpful. Not in the Wiki either:-)
I am combining a shower waste with a basin waste for layout reasons. The basin waste will join through a *flowed* T but I believe a non-return valve will also be necessary. I can just about achieve the 18mm/m fall and currently plan a conventional water seal trap for the shower waste.
The options seem to be:-
HEPvO plastic in line tit.
McAlpine T28M-NRV
The only adverse comment on the HEPvO seems to be a concern about the use of a blockage clearing plunger.
So far, I have not found comment or operating principle for the McAlpine unit.
Any comments?