Hot water problems.

[WelshMan]

My friends motherinlaw recently had some bathroom taps changed. They isolated the cold feed to the hot water cylinder and turned off the incomming cold main. She is telling my mate that the hot runs ok for a small period of time then trickles out to basically nothing. I think there is a air lock on the feed from the cylinder to the hot water taps, would this sound plausable?. if so its just a case of bridging the cold/hot water taps and forcing some main pressure up the hot water. I am unsure of what system she has cos my mate doesnt know these things so it could be a Yplan or S plan.
What do you guys think?

 

[kirkgas]

y or s plan is the heating controls, so not relevant, yes it sounds either like an airlock or a problem with the valve on the cold feed possibly not opening fully after being turned off, bridge the hot and cold as you said, keep the water on for a couple of minutes, then turn off the cold and keep the hot running, the cold should run back down then clear the airlock then the hot should run properly, if the prob is with the valve then i think you will need a plumber

 

[picasso]

air lock or they have snapped the gate valve on the cold feed to cylinder, easy thing to do as they become fragile with age and not being used.

 

[WelshMan]

Kk thought it could be that. What would you use to bridge the hot/cold some 15mm garden hose pipe or something similar?