How to prime a pump ?

Z

zag

Guest
I have a new 12v water pump which is used to supply water around a campervan.

I have heard mention of having to prime a pump or or pumps being self-priming, but I don't know exactly what this entails and there is no reference on the documentation to whether it is self-priming or not.

Anyone out there able to shed any light ?

googling throws up any amount of catalog listings and discussion forums talking about whether a particular pump is self-priming or not, but I can't see any reference to how to prime a pump if the need arises.

In case the need to prime is a function of the distance the water is pumped or raised - the pump will be sitting at the bottom of a 100l water tank with about 40cms of a vertical rise, followed by a horizontal run to the various outlets around the campervan - I guess there is about 10-15 meters of hose in all. The previous pump used to happily run for 10 or 15 seconds before water would appear at the taps if the water hadn't been used for a few hours.

Thanks for any help.

z
 
A basic Whale pump is not very good a sucking up water and depends on pumping out water to draw in some more to create a flow
Priming the pump means putting water into the pump to get the pumping started.
If you pump is at the bottom your tank it has water flowing in so it is primed when there is water in the tank.
If you were to fit pump above the tank with a pipe from the bottom of the tank to the pump. The pump would need to lift the water 40cm to the pump you would then need a pump that would self prime up to 40 cm. or greater if the distance were greater.
Manually primed pumps need you to put water into the pump to get the system going.You do this by pouring water into the outlet side of the pump to fill the pump and the pipe from the pump down with water. These pumps need a valve at he bottom of the inlet pipe to keep the pump primed when it stops and be ready for its next use. These one way valves allow the pump to take water in and stop it flowing out when the pump stops they are sometimes called foot valves.
The pump not the motor is lubricated by water so a self priming pump is designed to run for a short time until it sucks up water without damage.
Self priming pumps are usually more expensive than the basic pump. Manually primed pumps wouldn’t be suitable for Carvan use. The Whale type pump is popular for boats and caravans because they are dependable and can be run without water for a short time without major damage.

Roger
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Roger - thanks for that detailed reply.

"If you pump is at the bottom your tank it has water flowing in so it is primed when there is water in the tank" - on this basis I don't think I need to do anything other than turn it on since it will indeed be at the bottom of a normally full tank and won't have any length of hose 'below' the pump itself.

I think I (or maybe the kids) burned out the last one by running it dry for a while at the end of last year. I have just now got around to replacing it.

z
 
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