I bought a thermostatic valve like the one pictured but the hot and cold inlets do not have a typical compression fitting. What I was expecting was to be able to use a standard olive and nut compression fitting to connect my water supply to , but if you look at the inlets there is no groove for the olive sit in. It looks more like a standard shower hose nut which uses a rubber washer ( in fact the bottom bit is infact where you connect the hose to) but I can't for the life of me find the right nut to use. Any ideas what I should be looking for?