Need help troubleshooting low pressure

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Mrk3cobra

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I have a deep well jet pump used for irrigation. I just replaced the injector at the bottom of the well because I could not get more then 35 psi. Now the pump shuts off at 50 psi and cuts in at 30 psi, the problem is when the pump cuts in at 30 psi and the sprinklers are on the pressure drops instanly to 10 psi. I have a blue pressure tank. Any help would be greatly appreciated.

Pete
 

Reach4

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" the problem is when the pump cuts in at 30 psi and the sprinklers are on the pressure drops instanly to 10 psi."

Then what happens to the pressure?
 

DonL

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Sounds like the wrong size jet, or it is not getting proper pressure.

How are you controlling jet pressure ?

Or cut-in is not really what you think, where are you measuring pressure ?


Good Luck.
 
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LLigetfa

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...the problem is when the pump cuts in at 30 psi and the sprinklers are on the pressure drops instanly to 10 psi.

Let a few PSI of air out of the tank. You shaved the precharge too close and the tank is empty when the pump needs the water.
 

Mrk3cobra

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The pressure stays at 10 psi until I turn off the sprinklers then it goes up to 50 psi..
 

Mrk3cobra

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Sounds like the wrong size jet, or it is not getting proper pressure.

How are you controlling jet pressure ?

Or cut-in is not really what you think, where are you measuring pressure ?


Good Luck.
The pressure gauge is on the pump...
 

Mrk3cobra

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I will try and let some air out of the tank. How would too much precharge in the pressure tank cause the symptoms I have. Just trying to understand a little better.

Thanks, pete
 

Valveman

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Even with the wrong air pressure in the tank the pressure won't "dive" unless you are using more water than the pump can produce. I think you installed a high pressure, low volume jet assembly and now your sprinklers are putting out more than the pump can produce.
 

LLigetfa

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I think you installed a high pressure, low volume jet assembly and now your sprinklers are putting out more than the pump can produce.

That is a distinct possibility. A simple test is to take the cover off the switch and to nudge the pressure plate to get the pump to start well before the bladder hits the bottom of the tank. If the pump cannot keep up to the demand, there is no point in letting air out.

Jet pumps use pressure to make more pressure. If the pressure is let to dive too low, it can have problems to recover. Some jet pumps use a regulator to ensure the jet gets first dibs at the pressure. Other models have a manual diverter to help when starting from zero.
 

DonL

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If the pump does have a regulator, It may just need to be adjusted to match the new jet.

What is the model of the pump ?

They make different jet sizes for a reason, and that new jet may not match your pump.


Good Luck.
 

Mrk3cobra

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That is a distinct possibility. A simple test is to take the cover off the switch and to nudge the pressure plate to get the pump to start well before the bladder hits the bottom of the tank. If the pump cannot keep up to the demand, there is no point in letting air out.

Jet pumps use pressure to make more pressure. If the pressure is let to dive too low, it can have problems to recover. Some jet pumps use a regulator to ensure the jet gets first dibs at the pressure. Other models have a manual diverter to help when starting from zero.

I will test today...
 

Mrk3cobra

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The deep jet motor says on it 1/2 HP manufactured by GE. This is an old pump maybe 20 years old.
The new injector I bought came with 3 nozzles I think a 51,52,53 I used the 52 and the venture that went with the nozzle per the instructions. I can pull the injector back out and change the combination would I use the nozzle with a larger diameter or smaller. The water table is high the injector is only 25' deep.
 

DonL

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That pump may not be up to the job. GE made the motor, not the pump. Sounds like a one stage.

Does it have a regulator ? Close to where the gauge is ?

Did it work good before ?
 
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Mrk3cobra

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That pump may not be up to the job. GE made the motor, not the pump. Sounds like a one stage.

Does it have a regulator ? Close to where the gauge is ?

Did it work good before ?

the pump has no label on it. The regulator (the part that controls the cut in and cut out)is on the motor, and the gauge is on the pump.It has worked fine for me for the last 15 years.
 

DonL

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the pump has no label on it. The regulator (the part that controls the cut in and cut out)is on the motor, and the gauge is on the pump.It has worked fine for me for the last 15 years.

OK. The switch does not regulate the jet pressure. Some people use a ball valve, if the pump does not have a regulator.

You should look at your old venture / nozzle, and match it up with the one you install.

You could have other problems.

It is hard to tell from here.


Good Luck, You can make it work.
 
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Mrk3cobra

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There is no regulator the two pipes that go down the well are connected directly to the pump, which is only 1' from the well casing. Should I install the bigger or smaller nozzle to get more volume, I do not have the old injector anymore.
 

DonL

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You should check your tank to see if it has the correct pre-charge first, if you have not yet. Did you do that ?

If you are not pumping against a pressurized tank, with some back pressure, the jet may not get enough water to get it working properly, because the output is wide open.

I think you would want to go bigger, but I am no expert.


Good Luck.
 
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Mrk3cobra

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I will check the tank pressure when I get home today. I will also run a test with the pump running and the pressure at 40 psi I will turn on the sprinklers and see if the pump can maintain close to the 40 PSI or if it drops immediately to 10 PSI like it does when the pump cuts in at 30 PSI. I think this should tell me if the pump and injector are sized correctly. Does this sound like a reasonable test.
 
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