Undersized well pump - Looking for 2nd opinion/confirmation

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dsg

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I recently installed an irrigation system at a house I moved into last fall. I ran into a problem the first time I tried to run the sprinklers for an extended period and I'm hoping the experts here can weigh in on the diagnosis I received before I make a (possibly expensive) decision.

Here is the situation:

The house was built last summer, and the well was drilled 13 months ago. It was a spec build that I purchased after it was completed. I was not involved in the construction. About a month ago I started working on putting in a lawn. As part of that I put in an irrigation system. I have done this once before (successfully) at my last house with a well and similar sized yard. I used Rain Bird's design service for the design and installed everything myself. I'm not a pro, but I've read everything I can on irrigation systems and like to think I know what I'm doing. That being said, I know it is totally possible I made a mistake that has contributed to this problem.

The problem I'm experiencing is this: When I run the sprinklers they will work fine for anywhere from 7-10 minutes. At a certain point the pressure will start to drop to a point where the sprinkler heads go down and the gauge near my pressure tank will drop to nearly zero.

The irrigation system has a 11 zones all at 9 GPM. (I got about 9.5 GPM when testing the flow rate of the pump.) The main line is 1" PVC and it wraps around the far end of the house, probably 60-70 feet, gaining about 12 feet elevation at the far end. Laterals are 1 1/4" poly pipe. I have a RPZ backflow preventer at the POC, the heads at the other end of the yard are higher in elevation.

If I turn the system on and sit in the basement and watch the pressure gauge, it will deplete the tank, pump comes on at 40 PSI. It takes 5 or 6 minutes to slowly climb to 60, turn off, depletes the tank in 30 seconds or so, pump comes on again and it starts rebuilding pressure. At around 7-10 minutes total run time the pressure starts dropping and then eventually drops dramatically. At this point I usually shut down the sprinklers. Pressure rebuilds very slowly. I am not getting any air in the plumbing as far as I can tell.

The well 365' deep, static water level of 302'. The pump is an AquaDuty 10fv15 1.5 HP 10 GPM, 2-wire, 230 volt. (Screenshot of well record attached)

I talked to a local well driller and he looked at the stats on my well and pump and said the pump is too small. He said they would have used a more powerful 3-wire pump at that depth. I should not have problems running the well dry at the depth in the area I live.

My questions are:

- Does replacing the well pump sound like the correct solution? I have never had a problem with pressure loss in the house, but I imagine if it is undersized it will fail prematurely even without an irrigation system.

- Has anyone ever seen symptoms like this where it was not the fault of a well pump? I'm pretty confident there are no leaks and seems like that would cause consistently low pressure.

Any insight would be greatly appreciated, thanks in advance.
 

Reach4

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Your symptoms seem to be compatible with running out of water in the well. Monitor the current through one of the wires carrying power through the pressure switch. If the current drops when the pressure drops, that would tend to indicate you run out of water.

If the current rises, that would indicate another alternative.

Replacing the well pump does not seem like a reasonable solution based on your description.

I am not a pro.
 

Valveman

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Your pump builds up and cycles once while the sprinklers are running, which means the pump is putting out more than the sprinklers are using. So the fact that it falls off after 7-10 minutes is most likely pumping the well dry. You said you tested the well at 9.5 GPM, but for how long?
 

dsg

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Your pump builds up and cycles once while the sprinklers are running, which means the pump is putting out more than the sprinklers are using. So the fact that it falls off after 7-10 minutes is most likely pumping the well dry. You said you tested the well at 9.5 GPM, but for how long?

Not long. I did the bucket test a few times, timing how long it took to refill the pressure tank.

Is this a defect in the well that can be repaired? I have neighbors with houses built by the same contractor, same well setup who run irrigation systems with no problem. Also, wouldn't I be getting air in the plumbing if it were going dry?

Another piece of information - when we first moved in the water was cloudy for 2 or 3 weeks.
 

Valveman

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Use a ball valve and squeeze off the flow until the well can keep up. You need to find out how much the well can make when running 24/7. It is possible that the well can make 8 GPM, but your 9 GPM zones are drawing the well down. Once you know the recovery or production rate of the well, you can match the zones to that amount.
 

dsg

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Thanks, I'll try that. Also, test the current as Reach4 suggested.

Another question - In the well report, under Yield Test it says "Pumping level 330.00 ft. after 6.00 hrs. at 15 GPM". What exactly does that mean? That they pumped the well for 6 hours at 15 GPM and the water dropped to 330 feet?
 

Valveman

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Yes it should mean your well will make 15 GPM from 330' depth. If it is not doing that anymore the screen or filter pack could be clogged up, or the well has lost some production.
 
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