Self priming ???

I just bought a replacement jet pump for a house well. It is supposedly self priming. The definition of self priming isn't what I thought. It is self priming after the intake pipes and volute are filled with water. Self priming to me would mean that the pump could literally prime itself after all the plumbing was hooked up. There would be no need to fill the intake with water. Am I wrong or is the manufacturer stretching the truth?
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I thought they use to give a certain amount of "feet of head" that it would self prime. Today manufacturers seem to spend an awful lot of time coming up with deceptive terms to describe the power of the device
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RBM wrote:

There was one described that way. Other ads said self priming if the volute was filled first. One ad claimed the pump could handle air in the line.
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A jet pump will never be self priming. It uses part of the water to provide the lift. No pump can lift very far. If you want a pump that will work even when the lines have drained then get a submersible and put it down the well.
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Not being familiar with your particular pump ....is it deep or shallow?.... and jet pumps in general, but according to what I see on wiki, a jet pump is a velocity type pump, NOT a positive displacement pump. You need a positive displacement pump to pull a vacuum, therefore a prime. It appears a deep jet pump sits right in the water source, and therefore needs no prime. Perhaps that's what your supplier is calling "self priming". Either way, sounds like you've been conned, sorry to say.
http://en.wikipedia.org/wiki/Injector http://en.wikipedia.org/wiki/Pump
nb
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Someone educated me on positive displacement pumps and how much they can lift a while back. A perfect vacuum is about 32 feet of water at sea level so that is the absolute max that you can lift with any pump. No water pump can get anywhere close to a perfect vacuum. In practice lifting 20 feet would be amazing.
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jamesgangnc wrote the following:

i.e. USS Cole attack. Portable pumps could not siphon the floodwaters out of the engine room.
"The ship's small portable pumps could not boost the water out of the three-story-high engine room. Grasping for a crude solution, Peterschmidt suggested cutting a hole lower down--in the side of the ship just above the waterline. No commander relishes punching a hole in a wounded ship, and slicing steel was dangerous. With fuel thick on the surface of the water in the engine room, the risk of fire from a stray spark was grave. Reluctantly, Lippold agreed to cut the hole. The alternative, said Peterschmidt, was to "lose the ship." An enlisted man cut the hole; the ship did not burn; the pumps were able to get ahead of the flooding".
--

Bill - Former US Navy Metalsmith and Damage Controlman USS Salem Ca-139
In Hamptonburgh, NY
  Click to see the full signature.
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notbob wrote:

A deep jet pump has the jet at the bottom at the water intake. I don't know how you make it work without pumping water through the down pipe to the jet. Must be a check valve at the intake.
A shallow well jet pump has the jet attached to the pump. When the jet/pump are primed (just at the pump, not much water) it will lift the water out of a shallow well where the lift pipe is not full of water (limited lift as in james' post). It might be reasonable to call this self-priming. There is a check valve at the intake to normally keep the lift pipe full of water.
--
bud--

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That makes sense. The check valve keeps the pump immersed and also provides a enough of a seal in the pipe to pull a vacuum. I can see how a bad check valve (or flapper valve) could put the kibosh on the whole system. Perhaps the OP has neglected this issue. We didn't get much info from the OP other than, it don't work.
nb
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notbob wrote:

I haven't actually tried it yet. Self priming to me meant no need to fill the volute and supply lines with water before starting the pump. The directions with the jet pump said I need to do that. So I was wondering what "self priming" was supposed to mean. The set up we have is similar to the one on this page: > http://tinyurl.com/5s5md7w The well is only 25' deep. The pump and pressure tank are in the basement. There used to be artesian wells on this farm long ago. No need to pump water for livestock. The irrigation wells gradually took the water levels down so the artesian wells are history.
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