mixer shower help

[tonyn]

hi all this is my first post
I got called out the other night to sort a overflowing cold water storage tank after inspection the ball float valve is fine not passing, after a short while the lady of the house informs me, that it happens when they get a shower. After inspecting shower i find the cold is mains fed and hot water is gravity, So i suspect the cold water is back filling the cold water storage tank hence the overflowing. The shower is tiled in and pipework is inaccesible, My question is is it safe to fit a 22mm check valve on cylinder feed and would it work? if not any advice would be appreciated
cheers

[sonray ltd]

must be after the vent if you do.
but personally i would fit the cold to the cws and have balanced pressures

[tonyn]

i was thinking of fitting the check valve just before the gate valve on tank , would this be safe? thanks for the reply

[sonray ltd]

not really as your blocking the cylinders only expansion if the vent ever became blocked. and if the cylinder coil ever gos.

can you not get it on the shower hot supply only ?
or why don't they have the shower plumbed properly ?

[tonyn]

thanks very much for the reply and sound advice ill suggest the lady gets it plumbed in correctly , i knew something was niggling me about fitting check valve , as you say expansion becomes blocked potential bomb cheers again