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cahillprc2's avatar
cahillprc2
Explorer
Sep 03, 2020

Water Pump and Battery Question

While sanitizing my fresh water system and running water through the cold and hot supply lines, we had the lights on and when I opened the hot water faucets, the lights flickered and the water pump was much loader. When running the cold water lines the lights did not flicker. The water heater was not turned on at the time and was filled prior to running and water through the lines. The water pressure seemed to be low when running either the hot or cold water separately.

I checked the battery charge with a multimeter under no load it read 12.65; under the load from running the water through the hot water lines (when lights flickered) it read 11.96. I have two questions:

1. Do the meter readings indicate a problem with either the battery or the pump drawing too much power?
2. Why would the lights only flicker when running water trough the hot lines even though the water heater was not on
?
  • Since the pump load increases when running the hot water I'd check to see if you have a check valve on the outflow line of the water heater that is partially blocked or about to fail.
  • I don't know if the voltage drop is a problem. If only 1 battery, that doesn't sound too far off.

    As far as the hot versus cold water, I think it was hammering a little on a head of air as it fills the water heater tank. Most RV systems will hammer a little at first, until the system purges air, or at least compresses the bubbles of air.

    You might want to adjust the pressure regulator on the pump downward just a little. I've learned that when running on battery power only, the pumps sometimes struggle to reach the pressure setpoint with the voltage available. Less of an issue when hooked to shore power with a strong 12v converter keeping the voltage up. More of an issue without hookups as the voltage tapers down. A slight adjustment of the regulator makes it all happier, and the pressure you feel at a faucet is not even noticeable.
  • The reason for the louder pump is the hot water system is somehow restricted compared to the cold water causing the pump to work harder. That draws more amps causing the lights to flicker because of the weak battery.
  • A voltage drop that big on such a small load means your battery is shot.
  • Son's suggestions are good. I'm thinking the test of the pump will show a problem.
  • I would take the battery to an auto store and have it tested. Also check the battery connections and the pump wire connections. I would check the current draw of the water pump while it is running. Also, is the water valve to the hot water tank closed by any chance?

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