What size booster pump??

Discussion in 'Irrigation' started by CRUZMISL, Jun 12, 2005.

  1. CRUZMISL

    CRUZMISL LawnSite Member
    from zone 6
    Posts: 186

    I have a system that has a static pressure of 43psi. I'd like to see 60psi or so on the system if possible. I'll need a little less than 10gpm and the supply is 3/4 copper. 110V is also preferable. Any suggestions on a good quality pump? I don't know how to figure it out.

    Thanks,
    J.
     
  2. Jason Rose

    Jason Rose LawnSite Fanatic
    Posts: 5,858

    your static pressure really dosn't mean anything. you really want to know what your pressure is when flowing at 10 gpm (or whatever your target output is)

    Yes it can be done.
    Is the irrigation hooked to the same water supply as your house?
    Is the irrigation hooked up to the mainline before it goes into the house?

    I have done the same thing at my house. I used a 3/4 hp centrifigual pump (110 volt) and hooked it up so that it boosts the pressure for my irrigation. My concern was that the pump would actually suck more water thru the waterline than the meter could deliever and would create a negative pressure situation on my house plumbing. Never had a problem with that though. Even with the pump running full flow (like thru a open garden hose) I still have some, not a lot, but some, water pressure in the house. Good enough for me. My pump is hooked up to a outside faucet and then feeds the sprinklers. It's pretty hokey I admit, but I needed to get water on my lawn and didn't have the money or te time to install a complete underground system.

    The pump may have very well actually sucked the water out of my house plumbing if it was hooked into the mainline directly. As it is now there is a lot of flow restriction so it actually works out fine.

    Hope this helps. I know its not at all technical and probably as confusing as hell, but it's my jerry rigged way and I think it works great, and it saved me $1,000 bucks for a well, 220 wiring, and submersible pump.
     
  3. CRUZMISL

    CRUZMISL LawnSite Member
    from zone 6
    Posts: 186

    Actual running pressure is about 32psi. The line comes into the house at the front and then out the rear which is where the irrigation hooks in. Any tips on size pump, custom made or off the shelf???
     
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,997

    I have seen negative household pressure with lawn sprinkler booster pumps. There is a ($$$) way to avoid the problem, by boosting pressure for the entire house, instead of just the sprinkler system, by locating the pump after the water meter, and feeding a large pressure tank. Don't forget a check valve (maybe a dual check) to prevent backflow into the water meter and supply line. Doing it this way maximizes your possible flow and pressure, and allows you to share household use with the sprinkler system, without any worries about too-low pressures.

    With the pipe sizes and pressures you describe, a 1/2 HP jet pump in the sprinkler supply line would be more than enough for boosting pressure, and it might even be enough to create that negative pressure - if that were to occur, you'd switch to a 1/3 HP pump. I'd forget about 60 psi for the sprinklers. 40 psi at the heads would be more realistic.
     
  5. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    I like wet boots's scenario, I think you could avoid the pressure tank if the irrigation controller called for water (by pass with swing check around pump for normal use). One issue might be backflow......depending on what part of the middle of no where, adding a pump means an RPZ and that might be an upgrade.
     
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,997

    A booster pump is an important variable in backflow preventer considerations. Since it creates a higher pressure than the supply line, you would be in a backpressure situation. For a whole-house booster design, I would employ a dual check before the pump (some regions might require a double check valve assembly) and a pressure tank large enough to ensure that the pump gets a couple of minutes of rest between running cycles. No bypass, please, as that could be a backflow problem, although you could set up a bypass to allow you to switch out a pump while leaving the household supply still running.
     
  7. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    A bypass around the pump allows for full flow w/o pushing water through the pump when it is not engaged. With booster pumps, I employ this a lot for systems w/ drip. Turn the mv/pump switch off for drip zones and let the pump call for water. Backflow preventer for the system goes before the pump and by pass. A check valve in the by pass line prevents you from pushing water into a loop around the pump. If the controller calls for water and things are set up properly, I don't find the need for a tank, just a high pressure cut off in case a valve doesn't open.
    Running a by pass around the pump causes no back flow issue.
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,997

    My previous comment was for the whole-house booster configuration, which does require a pressure tank, in order to maintain a minimum off time for the pump between cycles. Pump motors need this off-time to get their full life. Naturally, pump and pressure switch settings are selected to provide continuous running when the lawn sprinklers are on. It's the non-lawn-sprinkler water uses that make the pressure tank a necessity on this configuration. Drip irrigation would fall into this category.

    With a booster pump plumbed to only boost the lawn sprinkler supply, while leaving the rest of the house alone, the pressure tank isn't needed to protect the pump motor, because you have it running continuously when the lawn sprinklers are running. (a tiny expansion tank, like what you see on hot-water heating systems, is a nice frill, and allows you to run the pump by way of the usual pressure switch control - no pump relay needed, except for when you have drip irrigation and you don't want the pressure boosted) - Many controllers now have a pump-operation setting, that will allow certain zones to run without the pump being turned on, assuming you have a pump relay in the circuit. The water for the drip zone can safely run through an unpowered pump, so a bypass might not have a real function here, except for maintenance.

    Where plumbing codes require protection against toxic backflow, the booster pump complicates backflow prevention. A two-stage approach is what I use. A dual-check before the pump, as protection for the city water against the higher household pressure, then after the pump, whatever the site requires, be it PVB or RPZ (Double Check Valve Assemblies aren't designed or rated for toxic backflow)

    Now, I'm working in basements with room for the pump and pressure tank. If my job site was going to require an RPZ anyway, and I was boosting pressure only for the sprinkler system, I could do without any dual-check. But since the RPZ is located outdoors, the booster pump would have to be out there, as well, downstream from the RPZ as required by code, and I don't like that configuration, and the extra electrical work that involves. Better to buy the dual-check, eat the five psi loss, and keep the rest of it simple.

    Installers in Double Check Valve Assembly areas may smile now. ;)
     

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