One isolating valve on both loft tanks inputs?

[phloaw]

Hi, just after the mains stopcock under my kitchen sink I have a tee, one pipe to drinkable water+washing machine and the other to the loft cisterns (talking about 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?

 

[steadyon]

1. No reason why there shouldn't be a valve on the input to the F&E tank. Clearly there shouldn't be one on the vent pipe.
2. If you are going to fit one, I'd make it a good quality, full bore lever valve, such as a Pegler.

 

[phloaw]

1. No reason why there shouldn't be a valve on the input to the F&E tank. Clearly there shouldn't be one on the vent pipe.
2. If you are going to fit one, I'd make it a good quality, full bore lever valve, such as a Pegler.

Thanks. This then brings me to a second question: any clue why my system currently has one valve in the loft only serving the storage tank?
I only see disadvantages in this choice, as compared to having one underneath the kitchen sink serving both loft cisterns: the latter i's easier to access, has less freezing chances, and you can serve both tanks with one valve.
I am just curious why the plumber originally chose to do that. Maybe the FE was added at a later time?

 

[steadyon]

Most likely added at a later date, and perhaps it was felt unnecessary to provide separate isolation. The usual trick was to tie up the float valve, but not much use if that was what your were changing!