Can I increase exiting irrigation pump pressure?


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Old 06-15-07, 10:34 AM
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Can I increase exiting irrigation pump pressure?

About a year ago I installed a shallow well outside irrigation pump for my lawn and garden watering needs. The well is 1 1/4" pipe, with a stainless sandpoint, down 40 feet deep. At installation, I measured about 23-24 feet of water down in the base of the well pipe.

The pump is a 3/4 HP "Red Jaclet", "impeller" type pump with a 3/4 discharge side. The pump pressure is around 25-28 # (gage is mounted on side of pump) and provides a steady stream of water @ about 4-5 gallons/minute.

The pump feeds into a 3/4" main line which is terminated with 2, 1/2 "Rain Bird" sprinkler heads (parallel mounted). While the system DOES provide adequate water, is there a way (short of replacing the pump with a high pressure pump) to increase the output pressure?
 
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Old 06-16-07, 06:53 PM
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Probably not. Pressure in any pump is the result of the fluid working against a resistance. In a centrifugal pump (which I'm sure is what you have) the pressure is going to be inversely proportional to the flow. If you were to increase the resistance after the pump outlet you MAY be able to increase the pressure but I suspect that the pump was designed for the pressure and flow rate at which you are using it.

If you were to remove one of your sprinkler heads (and plugged the fitting it was removed from) you MAY get more pressure but you would also be decreasing the flow, probably not what you really want.

I suspect the biggest problem to increasing the flow is simply where the water is. At 23 feet below the pump you are close to the working limit of the pump. The theoretical "lift" of a pump is only 29 feet and with piping losses the practical limit is less. With a driven well point you don't even have the option of using a "jet" pump.

Sorry.
 
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Old 06-17-07, 02:37 PM
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I get the impression you feel the volume is adequate, but perhaps want your sprinkler head's water to spray out water further? Maybe there is some way of restricting the size in the head itself to sort of create the similar effect of how you can shoot water out of a garden hose further if you put your thumb (restrictuion) over the end of the hose. ( By restricting the line leading to the sprinkler head will not accomplish this. It has to be in the head itself or a smaller holed head)

Another idea I got is where you could have your existing pump go into a small storage tank, and then use a high pressure pump (capable of 60 psi or so) to pull it out/pump it into a small pressure tank. But then there are the costs of such a set up.
 
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Old 06-18-07, 12:58 PM
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Increasing pressure

Thanks for the responses

Following your suggestions, I tried shutting off one of the two spinkler heads and "yes", there is a bit more pressure but not what I was searching for.

From what I can decipher from both of your responses, IF (big "IF") I were to replace my existing pump with a pump that has a larger discharge, wouldn't that be similar to reducing the size of the two sprinkler head restrictions? (Right???)

The other thought I had was to replace that existing pump with a "high pressure" pump (gear head or something that has a positive displacement and no "blow-by"). Am I on the right track with that thinking?

As another option, I also have a 2" dia. (inlet size) irrigation pump with a 1 1/2" outlet that could be put onto that well. The only concern there would be the pump is larger than the 1 1/4" well and I'm not sure that would work with that particular pump. What's your thought on that?
 
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Old 06-18-07, 05:01 PM
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You originally stated that your well is a driven 1-1/4 inch point and the water is approximately 23 feet down. That is the limiting factor. A pump with a 2 inch suction port will not be able to pump any more water than it can "drag" up that 1-1/4 inch well pipe.

Yes, a positive displacement pump, such as a gear pump, will definitely produce a higher pressure than will a common single-stage centrifugal pump under those conditions. Of course finding a gear pump with the desired specifications will not be inexpensive and it is still doubtful that you will be able to "draw" sufficient water from your well for the performance you desire.

It is really the depth of the water that is stopping you.
 
 

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