Weird water pump occurence

[Taranwanderer]

So I'm getting ready for this weekend's trip, and I fill the water tank. I flip on the pump to purge the air out of the lines. I can hear the pump is running, but it's not making it's normal sound or pitch. I open a tap and nothing--no pressure, no flow. The HWH is full, so it's not like there was an air pocket or anything preventing flow. I open every tap, hot and cold, and nothing, but the pump is still humming. So I open up my winterizing panel, uncap the antifreeze tube (which would seem to allow air to be sucked into the system,) and voila--the pump's pitch changes, pressure builds, and then the pump stops. I open the tap, and I have pressure/flow, pump kicks on again like it should. So what the heck was going on? It's like it couldn't get primed--almost felt like vapor lock on an old carburated V8. Thoughts? Is my pump on the way out? TIA...

[bubbles]

You said you uncapped the antifreeze tube but don't you also have a selector valve to switch between the antifreeze tube and your holding tank as an input to your pump?

[Flybob]

If uncapping the antifreeze tube allowed air to be sucked into the system, you had the winterizing valve in the winterizing mode.

[Taranwanderer]

Pretty sure the winterizing valve is set to the use position...I dry camped last month for a weekend, used water no problem, pump worked fine, and I haven't changed any settings. I'll double check it tomorrow, but I think it's set correctly.

I know, it doesn't make sense...

[B and B]

Taran,

I have had this happen as well. The winterizing valve in may case was closed. I forced water to prime the pump by filling the tank using overfilling pressure to force prime the pump. I guess the vapour lock comment is very valid as well, the antifreeze valve might be partially open and this is causing lack of prime.

[Filthy Beast]

I too have had this issue and I do not have the winterizing valve. I open one of the low point drains to solve it when it happens.