Why does my shower keep going cold?

[Bob04]

My shower has recently been getting colder and colder. Occasionally scalding hot water comes out for about 10 seconds and then it returns to cold. This happens every time I use the shower and no other water using appliances are on at the same time. The model is a aquatronic 2.

[trundler]

It sounds like the mixer valve is faulty. Generally there's a some form of thermostat that tries to keep the flow at a set termperature. It used to be done with bimetallic strip technology but nowadays its probably done electronically with a temperature sensor in the output flow and electrically operated valves to feed appropriate amounts of hot and cold water.

Thinking about your symptoms, I'd say the hot water valve is sticking closed. The scalding water comes out when it occassionally opens but then the system compensates, closing the hot water off and ramping up the cold. Because the valve is sticking, it then fails to open again to balance the flow.

Of course, it could be a single switching valve, in which case the explanation is the same as above but the cause is the valve sticking in the 'cold' position.

This is why I stick to baths :-)))

[spudqueen]

If you're in an older house it could be that you're on a common water supply and someone else in another house is using water - happens to me all the time!