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Old 09-28-2012, 04:25 AM   #1
s0394387
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Default Sand point well pressure

I have a new sand point well that that I have driven for an underground sprinkler system and have some questions. I am down about 32 feet and hit water at about 20 to 25 feet. I put a check valve right above the point (this might have been a bad idea). It is running off a 1HP shallow well jet pump and getting about 11 GPM straight out of the pump. I know that this will drop once I restrict the flow to get enough pressure. I am concerned about getting good pressure and not sure the best way to go about testing this. I am thinking that I can hook up a few above ground sprinklers with a pressure gauge attached but I don’t know if this will be an accurate method. I fear that I will find that I am unable to get the required flow at the required pressure to run the system. The zones are not laid out yet so I am trying to get this info to design my system.



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Old 09-28-2012, 12:50 PM   #2
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I am amazed you are getting 11 GPM. A single pipe jet pump can only lift from 24' max. Just put a tee with a pressure gauge before a ball valve. Then restrict the ball valve to hold back 40 PSI, and measure how much flow you are getting.



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Old 09-28-2012, 01:50 PM   #3
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I'm not sure how you got that point down with a check valve on top of it, apparently you didn't beat on it too much. Eleven gpm is pretty good, depending on what kind of screen you used. There is a large difference in types and brands.

The tee, gauge and ball valve is the easiest method to check your flow and pressure. Once you determine the flow, don't forget about friction loss through fittings, pipe etc. The pipe size and number of fittings can really drop pressure if you don't design it carefully.

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Old 09-28-2012, 09:08 PM   #4
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I'm confused about putting the pressure gauge before the valve. Isn't there different pressure before and after the valve?

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Old 09-29-2012, 07:00 PM   #5
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It doesn't matter, close the valve off until the gauge reads the pressure you need at the sprinklers then check the flow.

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Old 09-29-2012, 09:44 PM   #6
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Thanks for all the feedback
I did this and here are my results from my bucket test

@40 PSI = 11.11 GPM, @45 PSI = 7.89 GPM, @ 50 PSI = 3.13 GPM

I did about 3 or 4 time at each pressure and I think the 7.89 GPM is the one that might work the best. I have a small lot with about 1/8 acre (5575 ft^2) of grass to water. Any suggestions on the best pressure and flow to design to? From the info I've gathered 40 PSI is as lowest pressure I can work with but I could have pressure issues. With 8 GPM I would have more zones but it would work and 3 to 4 GPM will not work. I am not sure if I am on the right track so feel free to give me an ear full.

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Old 09-29-2012, 09:55 PM   #7
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As far as driving the pipe, I must have got lucky to not break the check valve and to get that good of flow. I am in Kansas and the soil in my area is pretty sandy for the first few feet but gets pretty hard around 8". At the hardest spot I was getting about 1/10" each blow with a 60lb post driver.

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Old 09-30-2012, 01:56 PM   #8
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Wow, I don't know how you didn't drive the pipe right through the threads on the valve.

Use the 40 psi reading and go a couple of gallons less for safety sake. Make sure your friction losses are very minimal and you should be good to go.



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