I need help with low water pressure on Jet pump

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Old 05-07-18, 03:47 PM
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I need help with low water pressure on Jet pump

Hi,
I am having an issue with maintaining water pressure on my jet pump. Here is my setup:
I have a 1 HP Red Lion jet pump with a 30/50 pressure switch. My inlet line from the well is 1.25" pvc pipe, and the discharge line is 1" pvc. The irrigation lines are 3/4" poly pipe to the sprinkler heads. The Pressure tank is properly set 2 psi below the cut in pressure (set at 28 psi). I have confirmed that the pressure tank holds air at 28 psi. The pump and pressure switch is about a month old (purchased brand new) and the pressure tank is 2 years old. I only use the pump to irrigate the lawn.

Here's my problem/question:
When I run one of the zones, the pressure cut-in switch will properly kick on at 28-30 psi, but then starts to drop in pressure after a minute or two. The pressure will fluctuates and stays on around 20-25 psi, and runs constantly at that pressure until the time is completed (usually 10-15 mins per zone). Every once in awhile it will decrease quickly to 20 psi then fluctuate back up to 25psi. All my zones do this. I'm not sure why the pressure drops to 20-25 psi in the first place. I even put smaller nozzles on the sprinkler heads, thinking it would increase the pressure by reducing the gpm.

Is it supposed to drop below the cut-in pressure at 30 psi? When the zone is completed and the pumps turns off, the pressure switch properly cuts-off at 50 psi. However, as soon as it turns off at 50 psi and the pump is off, the pressure decreases to 45 psi and stays there until I run the pump again. Can anyone help diagnose my problem or help me come up with a solution?

There do not appear to be any leaks. The check valve is close to the pump and is a few weeks old. So not sure what else to check. Should I get a new pressure switch (40/60) or increase the cut in pressure on the current one? Will that increase my pressure? Just not sure why the psi drops below the cut-in pressure. Any assistance would be greatly appreciated!
 
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Old 05-08-18, 08:24 AM
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It sounds like your zones are flowing more water than your well and pump can provide. You can confirm this by capping off half the emitters in a zone. Then run that zone and see if the problem continues. If the pump is able to keep up and goes up in pressure then you know you simply have too many emitters in each zone.
 
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Old 05-08-18, 09:06 AM
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Are you trying to simultaneously satisfy all five " outlets with water from the well's single 1" inlet ?

Maybe you need a timer to sequence the distribution so that they're not all drawing at once ?
 
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Old 05-08-18, 10:49 AM
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Pilot Dane, I'm sorry for not understanding, but not sure what you mean by capping off emitters in a zone. I have 3 heads on each zone. Each rotor head has 2.5 nozzles.

Vermont, I do have a timer, and each zone runs by itself at a designated time. No zones run together.

Thank you both for your replies.
 
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Old 05-08-18, 11:50 AM
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Remove the emitters/head completely and cap it off it so no water comes out. Basically cut a irrigation zone down so it can only spray 30-50% of what it used to. If the pump keeps up and can build pressure then you have a simple problem of too much irrigation and not enough supply.
 
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Old 05-08-18, 05:59 PM
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I even put smaller nozzles on the sprinkler heads, thinking it would increase the pressure by reducing the gpm.
That's basically what Dane is recommending.
Did the running pressure go up any when you tried this ?
 
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Old 05-09-18, 05:09 AM
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I think you still have too much irrigation outflow for your pumping system. Reducing the size of your emitters may have reduced the overage from 200% to 150% but it's possibly still too much. Most sprinklers with replaceable nozzles and especially those with multiple nozzles are more geared to commercial use and high flow.

---
One of the irrigation systems at my house uses a 5 hp pump to feed two impact sprinklers and each sprinkler has two emitters. At the lower elevations they run strong but at the higher areas of the lawn there's a noticeable reduction in pressure and performance so I'm at the maximum the pump can support. So, it is very possible that your sprinklers could be too much for your 1 hp system especially when you include the friction loss through the piping, 90 degree bends and valves.
 
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Old 05-10-18, 07:57 AM
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I understand what you are asking now. I will try that this weekend. But is the pressure supposed to drop below the cut-in pressure? For example, I have a 30/50 switch, and tank is set for 28 psi. But when I run a zone, it will start off at 30 for a minute or two, then starts to drop pressure to 20-25 psi consistently. Is it even supposed to do that?

Also, after the zone is completed and the pump shuts off at 50 psi (cut-off pressure), after a minute or two, the pressure reduces down to 45 psi and stays there. So I know there can't be any leaks because it holds at 45 psi in the off position. But what could cause it to go from 50 psi down to 45 psi and stop?
 
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