Gas water heater problem

[bobby62]

I have an old Vaillant gas fired water heater upstairs and it keeps cutting out half way through filling a bath or having a shower. Sometimes it will be ok and other days it will cut out after say 30 seconds of running a hot tap.

It may be me but it seems to be worse in the winter when I guess the water is coming in much cooled from the road.

I have to try and light the pilot every time this happens... very annoying.
I guess it is about 15-20 years old.

Could anyone tell me what may be the problem?

 

[namsag]

If you mean purely water heater and not combi boiler.

Is the pilot a strong flame and blue with no yellow about it.
It sounds as if your pilot is being drawn away from t/couple when the main burner comes on.

There was not many vaillant water heaters about but if memory serves me right they had no form of overheat protection on them which is what makes me think weak pilot