New system question

Discussion in 'Irrigation / Sprinkler Forum' started by jcheil, May 28, 2009.

  1. jcheil

    jcheil New Member

    Messages:
    1
    Ok, I have read almost every post in the archives but would still like clarification on the system I am attempting to install (brand new).

    I have 6 zones layed out. One zone requires 9.6GPM, 4 require 12.6 GPM and the last requires 13.1 GPM. Now these requirements are based on the labels on the sprinkler heads; most of which are pop-ups, 3 of them (1 in each of 3 of the zones) are popup impact heads. The pop-ups state 25PSI and the impac state 40-60PSI.

    All of the piping is 1" CL200 PVC pipe, with 1/2 risers (except the 3 impacts which are 3/4" risers).

    So, I am going to be using my old well (since the house is now on city water) and it will be dedicated to this irrigation project. It is a 2" well but T's off at the top of the well head to a 1" pipe and a check valve. (I am thinking this 1" reduction in size may become a problem?).

    This 1" pipe from the well head T goes to the 1-1/4" inlet (with a reducer) of a 1/2hp pump (about 45' away horizontally) connected to a 40 gallon pressure tank to which the pump is mounted on top. Not sure of the model number of the pump, but the brand name is a Red Jacket and I am 99% sure it is a Jet Pump just by comparing the looks of it vs centrifugal pumps on their website. It is the most typical well pump you see doen here in South Florida. I am also pretty sure the well is no deeper than 20'. The outlet on the pump is 1" also and as I said before, EVERYTHING is 1" CL200 PVC pipe after the pump.

    Ok, so I hope I painted a good picture of what I have.

    It is important to note that this is a new system and has never been used/tested. I have all of the pipe in the ground, washed out and the heads on but it is not connected to the pump and valves yet. I know that the pump/tank works because it was used for the house for several years (although not sure what the pressure switch is or should be set at now that it is being used for irrigation).

    My concerns (that I am aware of) are:

    1) Is the 2" to 1" conversion at the well head an issue. SHould I remove it, put a 2" T/cap on the well head and run 2" to the pump. I am not afraid to dig AND I want to drop the well head below ground level anyway because I am tired of tripping on it.

    2) Will the 1/2 pump stated above be enough to run what I have designed. I have no problem buying a new (correct pump) if needed.

    3) Would I still use the pressure tank (with either the existing or recommeneded new pump)? If so, what should the pressure switch be set at?

    4) Backflow - Since it is a dedicated well only for irrigation, is this needed?

    5) Check valve - Should it be at the well head or moved to the pump inlet or does it not matter.

    6) Anything else that I may not know of

    So anyone that could offer advice, I thank you in advance for the help, and since my speciality is computers, perhaps I can repay the favor for someone in the computers forum.

    Jay
  2. upper

    upper DIY Senior Member

    Messages:
    154
    Location:
    Fresno, CA
    zones

    How about this,turn the flow control down on the valve.Turn that valve on.Watch the pressure gauge as you turn the flow control lefty lucy.Check for coverage and that the pump stays running while the zone is on.What pressure does it run at?Is it enough?If not more zones are needed.If the pump cycles then bigger nozzels,or more nozzels are needed.Hope this helps Upper
  3. drick

    drick In the Trades

    Messages:
    392
    So you designed and installed a whole irrigation system without determining the GPM output of your well? It doesn't matter that you can go out and buy a 20 GPM pump if the well only produces 5 GPM.

    In any event.....

    1. One inch sounds small for an intake. What is the intake size at the pump? Go with that or larger.

    2. 1/2 sounds small for 13 GPM, but maybe its fine. Keep in mind though that the pump may be sized to the output of the well and installing a larger pump could run the well dry.

    3. I'd remove the pressure tank and pressure switch and use your irrigation controller to turn on the pump (you'll need to buy a pump start relay) UNLESS you want to add hydrants to use a garden hose. In that case you'll still need the pressure tank/switch. Set your pressure switch to 60/40 if you are leaving it in. I doubt 60 psi will cause you any problems even with the lower rated heads. I also doubt you'll be able to maintain 60psi on any zone with your current pump so I wouldn't worry about it too much. (They make inline pressure reducers as well as valves with built in pressure reducers if it comes to that)

    Leaving the pressure tank/switch can be an issue though. You do not want the pump to cycle on and off while the sprinkler system is running. Constant cycling will shorten the life of the pump. One approach may be to set the cutoff pressure high enough so that the pump cannot reach it as long as the irrigation system is running. Another would be to use a cycle stop valve.

    4. I'd remove it. Its costing you a couple of PSI your sprinklers might like to have.

    5. You should have a foot valve at the bottom of the intake for the pump. That is it. No other check valves.

    -rick
    Last edited: Jun 3, 2009
  4. upper

    upper DIY Senior Member

    Messages:
    154
    Location:
    Fresno, CA
    Boy my above post does not belong here,sorry.Precip rates for rotors and sprays are drasticllay different.Rotors need more minutes.A rotor on a spray head zone,needs to have all together different water needs..Upper
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