Today I'm going through an all systems check on my new TT. Hooked up water, made sure plumbing worked, hot water heater, etc. I put some water in the fresh tank (found a leak at the drain valve area, appears to be hairline crack on the tank) Anyway, ran the water pump all was fine. Here is where I messed up. I drained the fresh water and left the water pump switch on by accident. Realized I left it on 6-7 hours later. I heard it humming and said ****! Here is what confuses me.... Why would the pump hum when there was no call for water? It didn't have the loud pulsating chatter when it pumps, just a quiet purr. During my testing, turn on faucet and pumped activated. Shut off faucet and pump went quiet. I don't know why it was humming when there was no call for water. I put water in the tank and tested it again and it worked. How much damage do you guys think I did to pump?

If it's working, it ain't broke....enjoy the trip./...Dennis

If it works now, you probably just shortened it's life. The pump runs until it establishes water pressure in the lines. If there is no water in the tank, it can't establish water pressure, so it continues to run. Under normal conditions, it establishes pressure as soon as you turn off the faucet. Turn on the faucet and the pump runs trying to establish pressure.

The pump failed to prime, therefore was not creating pressure in the system, not even air pressure. The pump relies on water to cool itself. Odd that it ran for so long... Only way to know what, if any damage, is to run it again with water. Sounds like it worked, so I would continue to keep karma in my favour...

I don't believe you've done any damage at all to the pump. The reason it was humming was that it didn't have enough water to pump up to pressure. It was trying to pressurize the lines, and all it was drawing was air.

TucsonJim wrote:I don't believe you've done any damage at all to the pump. The reason it was humming was that it didn't have enough water to pump up to pressure. It was trying to pressurize the lines, and all it was drawing was air.Won't continuously drawing air damage the pump? Burn it up so to speak?

Rookie Mistake | Good Sam Community

RRBob
Explorer
May 05, 2014
wa8yxm wrote:

(Water does not compress, what compresses is the air cushion in the water heater, Thus providing the back pressure needed to shut it off.. If you really need to understand why it works I can explain but ... Well, enough typing already for one post.

If that is the case, why does my pump shut off when I have the water heater by-passed?
Homer1
Explorer
May 05, 2014
Always keep a spare water pump on hand. Cheap insurance.
ScottG
Nomad
May 05, 2014
Those pumps are of a hydrostatic design and will not overheat running dry (water is not used to cool them). Mine ran in an enclosed area for two full days and 4 years later it still works fine.
Campfire_Time
Explorer
May 05, 2014
I once drained my tank after sanitizing and forgot to shut the pump off. Days later I walked by the trailer and heard a faint humming sound. Duh! Anyway once I got it re-primed it worked fine for years. We traded that trailer last year and nothing was wrong with the pump.
tpi
Explorer
May 05, 2014
I had it happen one night where I parked the unoccupied trailer on a slope. Water tank was low and pump kicked on overnight and ran until I found it the next day. No damage to pump, it was fine for next five years.
12thgenusa
Explorer
May 05, 2014
RRBob wrote:
wa8yxm wrote:

(Water does not compress, what compresses is the air cushion in the water heater, Thus providing the back pressure needed to shut it off.. If you really need to understand why it works I can explain but ... Well, enough typing already for one post.

If that is the case, why does my pump shut off when I have the water heater by-passed?

The pump does not "need" the air pocket in the water heater tank to build up pressure in the tank and trip the pressure switch. After the flow of water is turned off when the pump is running, pressure quickly builds and trips the switch. Water is not compressible, but there is a slight "give" to all the pex water lines.

Many folks like to install a small pressure accumulator in the system. This allows for a longer water flow from a tap before the pump comes on. The pump also runs slightly longer after the tap is closed to recharge the accumulator. It reduces pressure bumps in the system.
Vulcaneer
Explorer
May 05, 2014
I think a "rookie mistake" is a mistake that one has never made before. So in that context, we all are making rookie mistakes throughout our lives. We have RV'd for longer than I can remember. But still make rookie mistakes all the time.

As opposed to "veteran mistakes." Those are the mistakes we have made before, but repeat them again. I really hate it when I make one of those.
mlts22
Explorer
May 05, 2014
Most water pumps are diaphragm pumps. The water doesn't actively cool them, just passes through two check valves and the diaphragm. Now, if the water pump were an impeller design like a macerator pump, it would probably burn itself out in 20-30 seconds.
B_s_Bunch
Explorer
May 05, 2014
Homer wrote:
Always keep a spare water pump on hand. Cheap insurance.
that is why we own two motorhomes:B

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