Hot water from cold taps

[malc]

Hello , just had a call about hot water coming from cold taps. Customer has called someone who can`t get there till tomorrow and asked me if i can fix it today. I have time this afternoon but just wondered if anyone can help me narrow down the fault before i get there to save time on fault finding please. They said it happened years ago too, and at the time it was the thermostat, could it be this again ?
all help or advice gratefully received thank you.

 

[PlumbBobBob]

if the cold is tank fed it is entirely possible that the thermostat has failed in the immersion, boiling the hot in the cylinder and backing back up into the cwst in the loft.

 

[jtsplumbing]

if the cold is tank fed it is entirely possible that the thermostat has failed in the immersion, boiling the hot in the cylinder and backing back up into the cwst in the loft.

Make sure that any replacement heater has a High limit cut off ! be a good idea to check the storage tank ! the older ones have been known to collapse !