Shower temp fluctuations on pump

[Skater]

We're camping in colder weather right now, so we filled the water tank and are using it instead of city water. We've noticed both on this trip and when we were camping over Christmas that the water temperature while showering fluctuates drastically - between cold and too hot - without touching the handle. Is this normal on pump operation? I'm guessing it has something to do with the pressure fluctuation... It maintains the set temperature when connected to city water.

[masseyfarm]

Is that what your lady might call a "CHANGE OF LIFE EXPERIENCE?"
I don't know what might be the problem but it is not normal. Are all the valves fully open and the bypass closed at the HWT?
Dave

Originally Posted by Skater

We're camping in colder weather right now, so we filled the water tank and are using it instead of city water. We've noticed both on this trip and when we were camping over Christmas that the water temperature while showering fluctuates drastically - between cold and too hot - without touching the handle. Is this normal on pump operation? I'm guessing it has something to do with the pressure fluctuation... It maintains the set temperature when connected to city water.

[Silver Goose]

Since the city water inlet and the pump outlet are essentially a common connection, the shower temperature shouldn't fluctuate with pressure variation, in theory.

That said, you may have a common type of pump that turns on at a low pressure point and off at a high pressure point as determined by the pressure switch. There is a normal air pocket trapped in the top of the hot water tank that by its existence acts as a cushion and while I can't grasp at the moment why this might contribute to your symptom I would try this. Allow the water heater to cool down, turn off the pump, open the temperature pressure relief valve (pop off valve), remove the drain plug to drain about a gallon or more of water. Replace the plug, allow the temperature pressure valve to snap shut, turn on the pump to allow the water heater to fill to re-establish the air pocket, turn on the water heater and test once hot.

That's my best guess.

[Skater]

I'll double check the bypass valves, thanks. I probably won't go to the trouble of draining some water out of the heater, but thanks for the suggestion - just too much trouble and I'm always afraid that plastic plug is going to break, and I don't have any spares at the moment.

[Skater]

We're still on this trip, so I didn't have the chance to update this, but:

1. I checked the valves, all tight.
2. When we got to our destination, I hooked up to city water and the temperature fluctuations went away.

It has to be something to do with the pump and its pressure fluctuations.