Well pump and City water

Discussion in 'Irrigation' started by Ground Master, Jul 19, 2002.

  1. Ground Master

    Ground Master LawnSite Senior Member
    Messages: 505

    Bid a fairly large system (58 rotors, 24 sprays) that will run off a well.

    Homeowner now wants system to be able to run off well OR city water.

    The easy way is to turn the city side off at the back flow and the pump side on , or vice versa. By "on" I mean physically turning a ball valve so as not to mix water supplies.

    Was trying to figure out a way to totally automate this with just a "flip of a switch". Could these manual valves be electric control valves? i.e. could I install electric valves after the pump and after the backflow that are either open or closed depending on desired water supply? I'm thinking that an electric valve used in this manner may not hold up? For instance if the well is being used, the electric valve after the city water backflow would be closed of course but water pressure from the pump side would be exerting pressure against the outlet side of this electric valve. Comments? Ideas? thanks, Tom
  2. DanaMac

    DanaMac LawnSite Fanatic
    Messages: 13,226

    My brain hurts thinking about it. Sorry no help.
  3. Ground Master

    Ground Master LawnSite Senior Member
    Messages: 505

    Mine too, Danamac. I think I'll stick with ball valves.
  4. DanaMac

    DanaMac LawnSite Fanatic
    Messages: 13,226

    One thought. With most systems off a well, a pump relay is installed between the pump and timer. If you are using city water but the same time, the relay will still come on and kick the pump on. Doesn't sound like a good idea.
  5. Planter

    Planter LawnSite Member
    from Utah
    Messages: 214

    Don't know what your laws are, but here we need a physical disconnect. We manually unplug one and plug in another.
  6. Tony Harrell

    Tony Harrell LawnSite Senior Member
    Messages: 739

    I just got city water last year. The well cannot be connected to the city water in any way. I guess they're afraid of backflushing and contamination.
  7. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    I don't think National Plumbing Code will allow cross connection. Why would anyone want to run a large system on city water?
  8. JasperStorm

    JasperStorm LawnSite Member
    from WA
    Messages: 71

    I have a large system in the city run off a well and I am not allowed to have the well line and domestic line hooked to the system simultaneously, regardless of having backflow devices. One can be hooked in, and the other must be physically cut and stubbed.
  9. gusbuster

    gusbuster LawnSite Bronze Member
    Messages: 1,932

    Our county is supplying to our residential customer(only selected areas) recycled water to use. A flat fee of $300 a year. One of the conditions is your irrigation has to be inspected and certified to make sure it is disconnected from city or county water lines.
  10. MikeK

    MikeK LawnSite Member
    Messages: 145

    Be careful here.
    First of all, does the well really have enough flow and pressure to accomplish watering this much ground.
    If it's like mose residential wells, the pump is just large enough to run the house and not to irrigate the entire lawn.
    With 58 Rotors, I'm gessing you have about 1.5 acres to water.
    Let's look at this from a different angle for a moment.
    It's best to have at least 10 GPM at 40 PSI to run an irrigation system. Using 1 1/4" main line, you will probably have about 30psi at the head when it's all said and done, not the best but workable.
    I would check the well to make sure it is putting at least this much out, Hook your flowmeter to an outside spigot and let the water fly until you hear ( or feel through the spigot) the pump kicking on, now back down on the flowmeter until you get to 40psi and take the flow reading. My guess is that it will not be as much as you think.
    Now, IF you have 10 GPM and IF the lot is 1.5 Acres... There is 27,152 gallons in an acre inch of water. Most lawns need at least 1 inch of water a week ( minus whatever mother nature gives).
    In the dryest part of the year, that means that the lawn would need 40,728 gallons a week. At 10gpm, you will have to run the system 67 hours a week or about 9 hours a DAY. Not too good.

    I would pick the water source with the best flow and pressure and use that.
    Also, using 2 different sources could present many problems with scheduling, ect. I don't think this is a path you want to go down.
    Let us know how it turns out

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