Megaflow Hot Water problem

[TheMrs]

Problem has built up over 2-3 weeks with our Megaflow system.

Currently turn the hot tap on and you'll get hot water for about 10 seconds then it will go cold and stay that way. Turn the tap on more it will get warm but not hot.

Shower still works (non electric) but to get the same temp you have to use more hot tap and open the tap more.

This morning noticed something else. Turn basin tap on, runs hot for 10 seconds then cold. Flush the toilet in the same bathroom and suddenly my cold running hot tap goes warm/hot again. Toilet fills and it reverts to cold water. Flush toilet again and water runs warm/hot.

Any ideas?

 

[picasso]

Something is allowing the cold water to pass into the hot supply, usual suspect is sticking a non return valve in shower valves, can you isolate your shower supplies ?

 

[Daveydub]

Or, does your cylinder have a thermostatic mixing valve? Mixes cold water back in to hot water to limit the temperature at the taps. Photo of cylinder and ancillaries may be helpful.

 

[Servotech]

Problem has built up over 2-3 weeks with our Megaflow system.

Currently turn the hot tap on and you'll get hot water for about 10 seconds then it will go cold and stay that way. Turn the tap on more it will get warm but not hot.

Shower still works (non electric) but to get the same temp you have to use more hot tap and open the tap more.

This morning noticed something else. Turn basin tap on, runs hot for 10 seconds then cold. Flush the toilet in the same bathroom and suddenly my cold running hot tap goes warm/hot again. Toilet fills and it reverts to cold water. Flush toilet again and water runs warm/hot.

Any ideas?

Try pulling some hot water through the pressure/temperature release valve.
What method do you use for heating up the water?