hot water turns cold

[andrewbadass]

HI CAN ANY BODY HELP OUT THERE GOT A VALLIANT BOILER JUST FITTED STEAM SHOWER
WATER STARTS OFF WARM THEN GOES ICE COLD BOILER STOPS HEATING WATER. GO DOWN STAIRS TO KITCHEN SINK TURN HOT WATER ON THEN BOILER KICKS IN AGAIN HOT WATER GO BACK UPSTAIRS TUNR ON SHOWER BOILER STAYS ON FOR COUPLE OF MINITES
AND WATER GOES COLD BOILER DOESNT WORK AGAIN ... GO TO KITCHEN AGAIN TURN HOT WATER BOILER KICKS IN AGAIN
FED UP ANYBODY HELP PLEASE THANKS ANDY

 

[clf-gas]

WHICH MODEL IS IT (BOILER).
POSSIBLE DIAPHRAGM FAULTY...

Oh and turn your caps lock off, we hate it

 

[holty]

could be a flow restriction on the pipe work

 

[plumgas]

plate heat exchange may be blocking wot model is it

 

[andrewbadass]

VALLIANT 12 YEARS OLD

DONT KNOW MODEL

 

[andrewbadass]

could be a flow restriction on the pipe work

NEW PIPE WORK FROM BOILER

 

[holty]

could be to good of a flow and the boiler has no flow restrictor in it, usually common with bath taps at full rate,if you have a basin in the shower room ,do the taps to the basin work, try cutting the flow down on the shower , some steam showers require high flow rates say 15l a min