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Discussion in 'Irrigation' started by Bobcat s250 NY, Sep 11, 2005.

  1. Bobcat s250 NY

    Bobcat s250 NY Banned
    from texas
    Posts: 98

    Hey guys i have a question in reference to an upcoming job. It is a 6 acre plot that has some very tight planting areas in which the irrigation plan is calling for the use of Netafim Drip. My question is that the system will run off a well. According to the plan the system has been designed to have rotary zones operate at ~55 gpm @50 psi. In the to be drip zone which are not very big at all what can be done to prevent the well from cycling on and off when this zone is on. I have heard of issues of wells that cycle on and off allot run into problems.

    Thank you in advance for your time
  2. MikeK

    MikeK LawnSite Member
    Posts: 145

    This is a tough one.
    Could you run the drip zones at the same time that the rotary Zones are Running?
    With a Hunter ICC controller, you can run program D and another program at the same time. Put the drip on Program D and the Others on Program A.
    If this would not work out, you could install a pump start relay on the well pump and make it stay on all of the time. You would then have to install a pressure relief valve somoewhere so that if for some reason the zone valve does not open, the well pump would have some type of protection.
    The only problem with this is that you could build up higher pressures on the well pump which could cause a problem with the pressure tank or damage to the pump.
    What about running the drip off of city water?
    Another solution would be to install a Vairable frequency drive well pump. THis would probably be the best solution
  3. Mark B

    Mark B LawnSite Bronze Member
    Posts: 1,020

    You could tie the drip zone on to the house after the pressure tank let the tank regulate the pressure. This should solve the problem. The only downside is that you will have to tie in under the house. I have done that before. I hope this makes sense.
  4. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    55GPM from a domestic well? Thats pretty impressive. Out here the best I see is 20 gpm or so.

    I don't usually worry to much about a drip zone cycling the pump. They usually put out about as much water as a homeowner turning on the tap once every 20 minutes.
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    Pump cycling is only a serious problem if the interval between pump starts is too short. The pump horsepower and delivery, and pressure tank drawdown volume will tell you what that interval is.

    Pump cycling can shorten valve diaphragm life, too, and flow control valves should be used for all zones, and adjusted for minimal valve opening.

    The idea of concurrent running is probably the most practical, if you want to completely avoid pump cycling. It will make system setup a bit trickier, as you will want to open the drip zone when adjusting the heads on the zones that will run when the drip is on.

    I'm guessing the pump is a five horse, which would be appropriate for six acres.
  6. Bobcat s250 NY

    Bobcat s250 NY Banned
    from texas
    Posts: 98

    As far as i know its a 6 inch well and has a 10,000 gallon tank. This thing is crazy. It is the same set up that i worked with last week at a concrete crushing plant. Its amazing what people call you to water.

    The reason i was concerned about the cycling was 2 yrs ago i installed a big system on a well and the homeowner installed a hosebib on the system and used it to wash his cars and stuff and i believe when the well guy came he had to replace the pump. He told him that it was due to the pump cycling on and off in short times.

    Also another question as far as mains the plan calls for 1 1/2 sdr. Do you think that will be big enough? So far there were many problems with this plan so far. I have been looking at flow charts and friction loss and its seems like if will be ok. for some reason it just seems alil to small for the job.
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    No way would 1 1/2" poly (or PVC) be enough for 55 gpm on a 6 acre plot. Way too much pressure would get lost in that main. The water velocity would be into speeds that could be damaging, even if you could stand the pressure losses. Much better to go to at least 2 inch, and if the mainline distance exceeds 500 feet, use a design with a looped main (a mainline that makes a full circle route around the property, which effectively cuts the pressure loss in half)

    As for cycling of pumps, a 10,000 gallon pressure tank is a thing I've never heard of. (take a photo of it, will you?) Are there no ordinary pressure tanks with this installation?, the kind that are refrigerator-sized at largest? It's the pressure tanks that give you the standby (pump off) drawdown capacity of a well installation.
  8. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    Who did this design? Landscape Architects are very often very conservative and undersize everything.

    Make the recommendations necessary on paper and present them to the owner. That way you won't be trying to fix it later.

    If you do loop the Mainline, you could get away with 11/2" PVC but it would be in your best interest to bump it to 2" and loop it. Much better flow and available pressure at the furthest valves.

    Are you pumping out of a 10000 gal storage tank, or are you tying directly into a well and the storage tank is nearby?

    As for running the drip zones on city water, you would need another backflow preventor as you cannot legally connect the two water supplies.
  9. sheshovel

    sheshovel LawnSite Fanatic
    Posts: 5,112

    There shoulden't be a problem with the drip making the pump cycle on and off.It's just like if the homeowner went in and took a shower once a day,the same as if you run the drip once a day.Most drip you don't even need to run that much,but even if you did it shoulden't be a problem.I have installed drip on many well systems and have never had a problem like wearing out a well pump because the drip made it cycle on and off.I think mabey your other well pump problem was not from your drip installation but from some other reason.I mean...how old was that pump that needed replacing anyway?
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    If there aren't any pressure tanks, then stand-alone drip operation on well water is out of the picture. I do see a number of well-pump-tank mismatches that allow short-cycling, but it's often a case of a larger pump replacing an old one, without an increase in pressure tank capacity to go with it.

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