Constant Pressure for Well System

Discussion in 'Pumps and Tanks Well Forum & Blog' started by gojoe3, Aug 4, 2007.

  1. gojoe3

    gojoe3 New Member

    Messages:
    68
    Hello,


    I have been researching how to best control consistent water pressure and flow in relation to my current home water purification system, but more importantly for a projected irrigation system at my home.

    Consistent pressure and flow is satisfactory until I use a sprinkler to water my lawn. I have a similar situation on a current project I am working on, with a new irrigation system and a master bath which will require good pressure and a high flow rate.
    I will be installing an automatic irrigation system in the near future and want to upgrade my current system. This all began when I decided that I should replace my amtrol 44 gallon pressure tank because it is the only original component in my system. While researching pressure tanks I came across products which claim to deliver constant pressure over a broad range of flows. The Flexcon Smart Tank with storage capacity and the CP Water MonoDrive by Franklin were my initial choices.
    I was then directed to review The Davey and Grundfos pressure boosting pumps after contacting a couple of local water professionals.

    I designed and installed my own water purification system aproximately five years ago. After hundreds of hours of research, a few upgrades and modifications, annual testing and maintenance, I have a system which performs its functions adequately.

    The water used for my projected irrigation system need only be filtered and will not be processed through my purification system.

    Preliminary water test results provided the necessary component choices. I needed to reduce the iron (.95-1.76 mg/L) and sodium (30-50 mg/L) from my groundwater and deal with color, turbidity (11-16 NTU) and pH (6.0-6.5 SU).

    My current configuration (in order): 1/3 hp submersible pump with 1" pipe (aprox 4.5 gpm pre-system output), Clack pvc venturi-type air injector, Amtrol WX250 pressure tank (40/60 low/high), all piping is now 3/4", off-air tank w/pressure release valve, pH neutralizer with auto backwash control valve (calcite/corosex, 50/50 mix), water softner with fleck 7000 valve, 4 stage r/o with permeate pump and 90% shutoff at kitchen sink. Lawn and garden water is separate from this system and is filtered for sediment only.

    I would like to ask if anyone could suggest an appropriate component to compensate for the pressure drop when the well pump calls for more psi. The simplest application seems to be the Franklin MonoDrive, but it is made for 3/4 to 1 hp pumps and I only have a 1/3 hp and need a new pressure tank anyway. The Flexcon Smart Tank seems ideal but I don't know how to compare it to the booster pumps for my needs. Also, I would like to ask for opinions on whether or not to use a high flow rate filter prior to the pressure tank to limit the amount of iron now introduced. Would a prefilter negate the impact of the air injector? Would it lower overall performance because of flow restriction or would it assist in keeping all components cleaner?

    Thank you for your time, best regards
  2. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    " . . . ask if anyone could suggest an appropriate component to compensate for the pressure drop when the well pump calls for more psi. "

    The well pump isn't calling for more psi; the system is letting more water flow out as more valves are opened. The characteristic of the pump is to deliver lower pressure when it is delivering more flow. Get a copy of your pump curve and you will see that if the flow is greater than about 150% of nominal capacity then the pressure will drop off quickly.

    If you want more flow at the same pressure that you now get at the nominal capacity of the pump, then you will need a bigger pump with more horsepower. You might be able to put a bigger motor on your pump with a variable speed drive. You would get more pressure but not much more flow.

    Before you add a bigger pump and an irrigation system you must determine the recharge rate of the well. You can usually pump a well for a few minutes at greater than its recharge rate, but you should never try to run an irrigation system at greater than the recharge rate.

    Pressure booster pumps don't increase the capacity of the well. They only provide increased pressure and flow for a short time while there is water in the casing. After that you are limited to the recharge rate of the well.

    From what I have seen of the Davey booster pump it is not likely to give good service. Others would be more direct and tell you that it is a piece of junk. Grundfos is a good name but they tend to be expensive for what they do.

    You have done a lot of work to set up your system, and I would suggest that you consider the following to manage your irrigation and household supply.

    1. Set up the irrigation controller along with the household system so that the household system has priority and the irrigation controller shuts down the valves when the pump is unable to maintain household pressure and flow demand.

    2. Because the household demand is usually small you can probably ingnore the quantity lost to the irrigation system. If the household diversion is too much to ignore, then let the irrigation controller keep track of the flow or time and deliver the correct amount of water to each zone.

    The result is that you don't need a larger pump and it won't affect you treatment system.

    I would figure out how to divert all of the irrigation flow before it goes to the irrigation system. There should be no need to even filter it if you are getting water from a deep well.

    I am rather surprised at the high turbidity that you report. Most drilled wells have a turbidity less than 1.0 NTU. Anything as high as 10 to 16 NTU is very turbid water. You will use a lot of filter cartridges if you filter your irrigation water to potable quality.
  3. valveman

    valveman Moderator Staff Member

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    4,369
    Location:
    Lubbock, Texas
    Last edited by a moderator: Aug 7, 2007
  4. Mr_Pike

    Mr_Pike New Member

    Messages:
    136
    Location:
    Nebraska
    When I saw 4.5 GPM it throws up a huge RED FLAG for Irrigation.

    What type of irrigation are you planning on installing, because you only have enough supply GPM to run about 2 heads at a time. If you are looking to install a standard turf irrigation system with rotor and spray heads, you are going to need a lot more storage capacity than your standard household pressure tank is going to supply.

    This can be done, but it is going to require a lot of design and extra materials not normally needed with a municipal water supply or well with a better output.

    As a side note, you might want to evaluate your overall need for irrigation VS your personal needs for water. I have seen people water themselves out of drinking water because they "needed" green grass.
  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    A cycle stop valve will not do anything to increase the flow or pressure. If you are losing pressure when the irrigation system comes on, and your well produces 4.5 GPM, the cycle stop valve will do nothing to solve that problem.
  6. valveman

    valveman Moderator Staff Member

    Messages:
    4,369
    Location:
    Lubbock, Texas
    The only thing that will keep the pressure up when you are using more than 4.5 GPM, is a larger pump. And this will only help if your well will produce more water. Then with a larger pump to solve you low pressure problem, you need a CSV to make it work like the old small pump when a little water is all you need.
  7. Mr_Pike

    Mr_Pike New Member

    Messages:
    136
    Location:
    Nebraska
    I have to say here that normally, a well pump is sized to match the available Gallons per minute. It is not a good idea to even suggest adding a larger pump to a well without also suggesting they first contacting someone who is qualified to test pump the well to determine the available water.
  8. valveman

    valveman Moderator Staff Member

    Messages:
    4,369
    Location:
    Lubbock, Texas
    As I said;

    "And this will only help if your well will produce more water."

    I agree. Can't use a larger pump if the well won't handle it.
  9. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    If the well is already producing at or near it's maximum, there is another method to connect a sprinkler system to it, and that is through a secondary collection tank, or set of tanks. These are not pressurized. They are just huge tubs of water. The small submersible pump runs to fill the collection tank(s), and the tank water is pumped by a jet pump to feed the sprinkler system.

    It isn't a really elegant solution, but it works in instances where a larger (than the original submersible pump can provide) volume of water has to be pumped onto a lawn in a certain time window, even if the original submersible pump is almost running 24/7
  10. Gary Slusser

    Gary Slusser That's all folks!

    Everyone seems to be going on about the 4.5 gpm. Yet we don't know the diameter or depth of the well. We do know a 1/3 hp pump.... so he may be seeing the 4.5 gpm because of the pump and not the recovery rate of the well.

    As to this:
    ***********
    Preliminary water test results provided the necessary component choices. I needed to reduce the iron (.95-1.76 mg/L) and sodium (30-50 mg/L) from my groundwater and deal with color, turbidity (11-16 NTU) and pH (6.0-6.5 SU).

    My current configuration (in order): 1/3 hp submersible pump with 1" pipe (aprox 4.5 gpm pre-system output), Clack pvc venturi-type air injector, Amtrol WX250 pressure tank (40/60 low/high), all piping is now 3/4", off-air tank w/pressure release valve, pH neutralizer with auto backwash control valve (calcite/corosex, 50/50 mix), water softner with fleck 7000 valve, 4 stage r/o with permeate pump and 90% shutoff at kitchen sink. Lawn and garden water is separate from this system and is filtered for sediment only.
    ***************

    Since you are only getting 4.5 gpm out of a 1" line, you probably have a serious flow problem, or pump problem or... a water leak.

    That 50/50 mix is way high/wrong and with a pH of 6.0, you didn't need a mixed bed to start with. Your pH should be sky high. Aeration increases pH too.

    The 4.5 gpm is insufficient to backwash most filters.... especially an AN filter.

    I'm not a fan of the Fleck 7000 after selling 25 of them and having more problems with them than with 442 Clack WS-1s at the time. Currently roughly 880 Clacks and so far only 18 problems. BTW, the 7000 programmed for variable brining uses many times the volume of water than the same size softener with the Clack WS-1.

    Describe the well; dia, depth, static water level, pump depth.
  11. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    You have set up your own system so I assume that you can figure out what I desecribe here.

    Let's assume that your current system is satisfactory without the irrigation load. Also, you have a known pump characteristic (4.5 GPM at the desirable pressure range) that is operating on a hydropneumatic tank with a pressure switch. It also assumes that operating at your current pressure range is satisfactory for household purposes.

    The first thing is to set up the irrigation system so it uses all of the water that the pump will deliver at somewhere in the range of about 48 to 58 psi. The precise number isn't critical but you want to aim for the mid to high side of the operating range.

    Now for the control system.

    1. When you want the system to irrigate, you operate the IRRIGATION controller to turn on the pump. As long as there is no household demand the pump will run and deliver irrigation water at a rate determined by the characteristics of the pump and the sprinkler system.

    2. When there is significant household demand the pump will not be able to keep up. At some point the pressure will quickly drop to the start pressure (40 psi). At that point your control system TURNS OFF the sprinklers but DOESN'T TURN OFF THE PUMP.

    3. The pump is now delivering only household water so the pressure switch will keep the pump running until the pressure reaches the PUMP OFF pressure.

    4A. If the irrigation system is demanding water when the PUMP OFF pressure is reached, then the valves open and the pump stays on.

    4B. If the irrigation system is not demanding water then PUMP OFF pressure is reached then the pump shuts off.

    To keep the system simple, I would ignore the reduction of total irrigation delivery when household uses are demanding water. That is probably an insignificant fraction of the irrigation demand. If it is significant then you could use a controller that would compensate for the time the valves are off.

    If the existing pump is big enough for your needs you should be able to manage the irrigation problem and save $1000 to $2000.
  12. Gary Slusser

    Gary Slusser That's all folks!

    2. When there is significant household demand the pump will not be able to keep up. At some point the pressure will quickly drop to the start pressure (40 psi). At that point your control system TURNS OFF the sprinklers but DOESN'T TURN OFF THE PUMP.

    The pressure tank is providing water until the pump comes on.

    A CSV and small pressure tank, they are nonelectric, is a much better solution and will cost much less than electronic controllers and electrical wires etc..

    Plus the CSV gives constant pressure for all water uses once the pump comes on.
    Last edited: Aug 10, 2007
  13. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    The point of the system that I described is that it allows using the full 4.5 GPM capacity of the pump to supply the irrigation system, and to also supply the household demand by setting up the system with "household priority".

    One could indeed put in a system with a larger pump and a CSV, but that would require a larger pump with larger motor.

    One solution requires only a relay control setup with the existing pump system; probably $50 worth of relays.

    The other requires a new submersible pump with bigger motor, probably a new down pipe and larger wires, a CSV, and the installation of all of that equipment.

    The owner can decide what he wants to do.

    Based on the original post, this IS NOT one of the cases where it might be said that the owner wouldn't know how to deal with such a system.
  14. Gary Slusser

    Gary Slusser That's all folks!

    The problem is he doesn't have enough water for the house let alone the irrigation.... He said: My current configuration (in order): 1/3 hp submersible pump with 1" pipe (aprox 4.5 gpm pre-system output),

    So he needs to fix his low flow problem, and if he doesn't have a leak, he needs a larger pump. Relays etc. don't fix the problem. Also, a garden hose uses more water than 4.5 gpm, so IMO he won't get irrigation to work with that low flow either.
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