Just after the mains stopcock under my kitchen sink there is a tee, one pipe to drinkable water+washing machine and the other to the loft cisterns. ( This is an open vented pumped S-plan system, standard here in UK )
I was wondering whether it is safe to add an isolating valve on the latter pipe, placing it right after the aforementioned tee ( I.E. under the kitchen sink ).
I am asking because I've read somewhere that the feed and expansion tank shouldn't have a valve on its input, but I couldn't find a consensus on that, online.
I am also suspicious because currently I have an isolating valve just before the bigger loft tank in the loft, not serving the FE tank. Which could be a hint that FE shouldn't have an input valve?