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Thread: Irrigation vs domestic pressure pump

  1. #1
    Architect Spaceman Spiff's Avatar
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    Default Irrigation vs domestic pressure pump

    I have a well that fills an underground tank. The house pressure pump then draws water from that to fill a pressure tank. I want to add sprinklers now for the lawn and garden. Can I tee off the pressure side and use the same pump or is there a better setup? Is a different pump better for irrigation than the pump I have? What should I be looking for and where should I start? Thank you!!!
    Spaceman Spiff aka Mike

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    Moderator valveman's Avatar
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    When you say the house pressure pump “draws” from the underground tank, I assume you have an above the ground pump like a jet pump. Yes this pump can probably also handle your irrigation. Figure out the size of pump and how many GPM it pumps at say 40 PSI, if that is what you want on your sprinklers. Then you need to carefully engineer your sprinkler system to exactly match the output of the pump. If it is a 15 GPM pump, then every sprinkler zones needs to be exactly 15 GPM. Then carefully program it to only irrigate during off hours when you would not be needing water for the house, because there won’t be any pressure left.

    Or you can use something like a Cycle Stop Valve before the tank and tee to the irrigation. This way you can irrigate at any flow rate you want, as long as you don’t run more at one time than the pump can keep up with. The CSV will also allow you to set your irrigation zones for less than the pump can produce, so you would still have water in the house even when the irrigation is running. If it is a 15 GPM pump, use sprinkler zones of 10 GPM or less, and you will always have 5 GPM left for the house. In this way you can match your sprinkler system to the yard, not the pump. The trade off here is that you will be paying a little more for electricity by irrigating at 10 GPM if your pump will do 15 GPM. It might cost you 10% more at the most, which would make a $30.00 electric bill go up to $33.00. The convenience and peace of mind of being able to use the water anyway you want, and have constant pressure to boot, makes it more than worth it.

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    Moderator valveman's Avatar
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    "21.3 GPM at 30 psi
    18.3 GPM at 40 psi
    12.5 GPM at 50 psi
    6.6 GPM at 60 psi
    Shutoff (zero flow) at 70 psi."

    If these is the same as the size pump you have then every sprinklers zone would need to be exactly 18.3 GPM to maintain 40 PSI. A larger zone would cause the pressure to be lower and the sprinklers would not shoot far enough. A smaller zone would cause more pressure so the sprinklers would shoot too far. Even if you can make every zone 18.3 GPM, you can't use water in the house at the same time or the pressure will lower and your sprinklers will not get the coverage you need. Then of course, any use less than 6.6 GPM will cause the pump to cycle on and off repeatedly.

    I would use a 40 PSI Cycle Stop Valve and set my sprinkler zones anywhere from 1 GPM to 15 GPM. Then the pressure will stay exactly 40 PSI all the time and the sprinklers will give you perfect coverage. You can even use up 3.3 GPM in the house while a big 15 GPM zone is being used, and the pressure will stay at 40 PSI constant. It might take you a little longer to irrigate your lawn but, who cares. With the CSV you can be irrigating all the time if need be and still have enough pressure in the house that you don't know the sprinklers are even on. You will even have a constant 40 PSI pressure for a single shower which is much more enjoyable than the pressure constantly going up and down between 30 and 50 PSI while showering.

    There you have it; An irrigation system that allows you to water the lawn anyway you want and still have steady pressure in the house. Without the CSV even a rocket science engineer can't make the system work smoothly, keep the pump from cycling, deliver a perfect spray pattern, and still have constant pressure in the house.
    Last edited by Terry; 04-17-2007 at 12:02 PM.

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    Moderator valveman's Avatar
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    Make and model of pump would really help to keep us from guessing.

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    If it were me SS, I would try to set the sprinklers up to work with the submersible pump. If you have 12 gpm, I'm not sure why you have a cistern in the first place.

    Rather than try to use a jet pump to run sprinklers, the sub would do a better job and your 15 hundred gallons will get you through while the sub is watering. You should water at night anyway to prevent evaporation. Unlessyou live in Michigan where it's always overcast.

    bob...

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    Moderator valveman's Avatar
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    Missed that one. Speedbump is right. If your well will make 12 GPM continuously, you don't need the cistern or booster pump.

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    Architect Spaceman Spiff's Avatar
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    My well pump is a Goulds 13GS05412 (1/2HP). It pumps a little over 12 GPM at 120' head at almost 0 PSI. Pump is set at 280' in a 328' well. My well pump installer picked that pump to be able to run continously and not run the well dry. He knew that I was going into a tank when he set the pump. When I restrict the flow the rate drops quite a bit so I don't think I can rely on this for sprinklers... plus I'd rather put as mush of the wear on a pump I can replace in 30 min. The well driller pumped 16 GPM cont. for 24 HR at 10' drawdown.

    The pressure pump is a Jacuzzi Cyclone 7CYS (3/4HP) with 1-1/4" fittings. I have a 1" poly pipe from my tank and 1" copper to bladder tank and a ball valve stub for sprinklers. (It was easy to add the tee and valve when I did the house, so I just did it )

    I'll get flow rates this weekend.
    Spaceman Spiff aka Mike

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    Moderator valveman's Avatar
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    "The well driller pumped 16 GPM cont. for 24 HR at 10' drawdown."

    I do not understand why the driller did not put in a 13GS10 which is a 1 HP pump that would have pumped the same amount of water but, at a pressure that would work for the house and sprinklers. Then you would not have needed the storage tank and booster pump at all. Does the well get weak in certain times of the year or something?



    "plus I'd rather put as mush of the wear on a pump I can replace in 30 min."

    Pumps are made to run. Running sprinklers will put no more wear on the down hole pump than on an above the ground pump, as long as the pump does not cycle on and off too often. Cycling on and off can now put excess wear on both pumps.

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    Moderator valveman's Avatar
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    CSV or not, I still don't understand why the system does not work straight off the well. The only reason for a storage tank and booster pump, is if the well produces less than the peak demand.

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    Architect Spaceman Spiff's Avatar
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    I own a few acres and might put another house or two on the well and tank. Sorry, forgot that bit.
    Spaceman Spiff aka Mike

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    The well driller pumped 16 GPM cont. for 24 HR at 10' drawdown.
    That is a perfectly good well and should be fine without the tank and extra pump. I agree with Valveman, you don't need the other equipment.

    I would hook it up to the existing pressure tank, add a CSV and be done with it. Sell the cistern to someone who really needs one.

    bob...

  12. #12
    Architect Spaceman Spiff's Avatar
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    HA HA HA...

    it's a rubber lined concrete tank, probablly 3000# and buried in the ground about 6'.

    I think i'll leave it.

    Plus it's a good way to settle out any sand or fines.

    Thanks for the help!
    Spaceman Spiff aka Mike

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