How do RV pumps work?

[Charlie]

How do RV pumps work?

A friend with an RV bought a pump and got an extra by mistake which Amazon
told him to keep so he gave it to me because he knew I always wanted to
build a solar hottub. <https://www.amazon.com/dp/B0DF7B1VYD>
"12V RV Water Pump Kit 20PCS, 4.0 GPM Camper Water Pressure Pump
with Pressure Switch, 45PSI Self Priming Diaphragm Pump with
Alligator Clips for Camper Yacht Marine Caravan Kitchen Bathroom"

I don't understand what the pump is for as I don't own an RV nor a Camper,
nor a Yacht or even a Caravan - but I do have a spa which I'd like to heat
with solar power in the summer months.

I connected that pump to an old car battery and it pumped water out of the
spa back into the spa via it's input and output garden hose connections.

If I buy a few hundred feet of black hose, I can probably loop it on the
ground next to the pool in the summer months to soak up the sun's heat.

But when I connected the input to a garden hose, nothing came out.
The pump didn't even turn on.

Given I'm not using the pump the way it's supposed to be used, I'm just
wondering what it supposed to happen when you hook a garden hose to it.

The description says it's supposed to pressurize that water.

But it doesn't do anything and yet when I disconnect the garden hose, it
works find in the manner I described above with one end in the spa.

How are these things supposed to work in an RV?

[Charlie]

Post by Charlie
How do RV pumps work?
A friend with an RV bought a pump and got an extra by mistake which Amazon
told him to keep so he gave it to me because he knew I always wanted to
build a solar hottub. <https://www.amazon.com/dp/B0DF7B1VYD>
"12V RV Water Pump Kit 20PCS, 4.0 GPM Camper Water Pressure Pump
with Pressure Switch, 45PSI Self Priming Diaphragm Pump with
Alligator Clips for Camper Yacht Marine Caravan Kitchen Bathroom"
I don't understand what the pump is for as I don't own an RV nor a Camper,
nor a Yacht or even a Caravan - but I do have a spa which I'd like to heat
with solar power in the summer months.
I connected that pump to an old car battery and it pumped water out of the
spa back into the spa via it's input and output garden hose connections.
If I buy a few hundred feet of black hose, I can probably loop it on the
ground next to the pool in the summer months to soak up the sun's heat.
But when I connected the input to a garden hose, nothing came out.
The pump didn't even turn on.
Given I'm not using the pump the way it's supposed to be used, I'm just
wondering what it supposed to happen when you hook a garden hose to it.
The description says it's supposed to pressurize that water.
But it doesn't do anything and yet when I disconnect the garden hose, it
works find in the manner I described above with one end in the spa.
How are these things supposed to work in an RV?

I got one and tested it, and found out how they're supposed to work.

You hook one end into a tank of cold water (like a spa or RV water tank).
Then you hook the other end into a faucet (which can be a garden hose).
You power it up.

If the outgoing garden hose is closed, nothing happens.

But if you OPEN the valve on the outgoing garden hose, then water starts
pumping (by magic I guess) by the pump from the spa or water tank.

If you CLOSE the valve on the outgoing garden hose, then the pump (again by
magic) senses that the output stopped so it shuts off the pressure pump.

The pumps don't even have on/off switches which is why it confused me.
They go on and off depending on if water is flowing out or not.

Don't ask me how they know that water is flowing though.

[Snag]

Post by Charlie

Post by Charlie
How do RV pumps work?
A friend with an RV bought a pump and got an extra by mistake which Amazon
told him to keep so he gave it to me because he knew I always wanted to
build a solar hottub. <https://www.amazon.com/dp/B0DF7B1VYD>
   "12V RV Water Pump Kit 20PCS, 4.0 GPM Camper Water Pressure Pump
    with Pressure Switch, 45PSI Self Priming Diaphragm Pump with
Alligator Clips for Camper Yacht Marine Caravan Kitchen Bathroom"
I don't understand what the pump is for as I don't own an RV nor a Camper,
nor a Yacht or even a Caravan - but I do have a spa which I'd like to heat
with solar power in the summer months.
I connected that pump to an old car battery and it pumped water out of the
spa back into the spa via it's input and output garden hose connections.
If I buy a few hundred feet of black hose, I can probably loop it on the
ground next to the pool in the summer months to soak up the sun's heat.
But when I connected the input to a garden hose, nothing came out. The
pump didn't even turn on.
Given I'm not using the pump the way it's supposed to be used, I'm just
wondering what it supposed to happen when you hook a garden hose to it.
The description says it's supposed to pressurize that water.
But it doesn't do anything and yet when I disconnect the garden hose, it
works find in the manner I described above with one end in the spa.
How are these things supposed to work in an RV?

I got one and tested it, and found out how they're supposed to work.
You hook one end into a tank of cold water (like a spa or RV water tank).
Then you hook the other end into a faucet (which can be a garden hose).
You power it up.
If the outgoing garden hose is closed, nothing happens.
But if you OPEN the valve on the outgoing garden hose, then water starts
pumping (by magic I guess) by the pump from the spa or water tank.
If you CLOSE the valve on the outgoing garden hose, then the pump (again by
magic) senses that the output stopped so it shuts off the pressure pump.
The pumps don't even have on/off switches which is why it confused me.
They go on and off depending on if water is flowing out or not.
Don't ask me how they know that water is flowing though.

I'd explain it but you probably wouldn't understand .

[Charlie]

Post by Snag
I'd explain it but you probably wouldn't understand .

If the restriction causes 43PSI backpressure it won't pump. Valve
closed, pressure over 43psi - pump off. Valve open, pressure below
43psi, pump turns on.
For your use you really want a "pony pump" but the RV pump can be
made to work

Thanks for the explanation that if the pump sees at least 43psi on the
outlet side it shuts off, otherwise it pumps water from the inlet side.

The unit came with a cigarette-lighter socket also for use in vehicles.

That's kind of neat as it can also be used as a portable outdoor garden
hose for watering plants which are far away from the house that you can
truck the water to in ten gallon containers (or whatever size you carry).

Looking up what a "pony pump" is, I'm surprised I never heard of them.
https://www.google.com/search?q=what+is+a+pony+pump

"Pony Pumps are famous for their compact portable flexible
impeller utility pumps and their versatile line of small submersible
pumps. Pony pumps are non-submersible, self-priming nickel plated
brass transfer pumps with Buna-N impellers. These lightweight,
pumps can be used to empty waterbeds, drain water heaters or aquariums,
pump out a basement, transfer water to an RV, pump boat bilges, pump
out stock tanks, and in other applications where water needs to be
transferred. Intermittent duty is 15 minutes ON and 45 minutes
OFF. Two extra impellers and gaskets included."
https://store.waterpumpsupply.com/ponypump.html

I wonder how they differ from the other liquid-transfer pumps though.

For example, this is billed as a 12VDC "self-priming diaphragm" pump.
https://www.amazon.com/dp/B0DF7B1VYD

And this is billed as a 12VDC "fuel transfer" pump.
https://www.amazon.com/dp/B0DFCRH64R

And this is billed as a 120VAC "water transfer" pump.
https://www.amazon.com/dp/B0D9W3VQNB

And this is billed as a 120VAC "submersible water draining" pump.
https://www.amazon.com/dp/B0D9B3MQB9

I'm not sure which pump I need for my application which is to have a
solar-powered spa heater that pumps water in the summer from the spa
through a few hundred feet of black hose back to the (now warmer) spa.