Adding a water storage tank to existing well

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by gwrace, Aug 27, 2008.

  1. gwrace

    gwrace New Member

    Aug 27, 2008
    I have a 20GPM submersible pump down approximately 260-300 feet. It feeds into an 86 gallon Well Xtrol pressure tank with a 30-50 PSI switch. That feeds into a Davey booster pump that supply's water to the house and a irrigation system. We are located in South Texas.

    I would like to add a 2500 gallon black Poly/Plastic water storage tank to the system. During the summer the irrigation system is able to pull more water than the pump can deliver.

    I was hoping someone could validate what I plan to do.

    20GPM Well Pump-->Storage Tank with manual inlet flow valve-->pressure tank-->booster pump

    Storage tank would be located approximately 20 feet from pressure tank.

    I have several questions:

    1. I'm wondering if I'll have enough pressure to feed the pressure tank without another pump in the system. There is a current rise of about 6 feet from pump switch to pressure tank. (Well Installer mounted tank up on a work bench and pump output comes in through wall at ground level)

    2. Does the manual float switch in the storage tank have an electrical connection back to the pump switch or controller. I'm just trying to figure out what switches off the well pump when the 2500 gallon tank is full.

    3. Any special plumbing considerations? I've seen some sites recommending flex plumbing, flow valves.etc? The tank is a Norwesco model D40631 with 1.5" intake and 2" drain fittings.

    4. We don't get very much below freezing temperatures but I plan to bury the water lines under ground and insulate the lines above ground. Any issues with this?

    5. Should I be concerned with filtering the water before and after it goes into the storage tank? Our water contains a lot of iron that I currently remove with a softener and whole house filter.

    6. Do they make devices for sanitizing the water with Chlorine? We probably will turn the water over frequently during the summer but it will also be used in the house.

    Sorry for the long post but just want to do this right the first time. Thanks for any assistance.

    Last edited: Aug 27, 2008
  2. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    You would need a float switch in the 2500 gallon tank. You don't need a valve in the tank. The float switch will control the pump, probably through a contactor or relay.

    I would want to look at the curve for the pump, and know the depth to water in the well, to determine if the increased flow you would get to the 2500 gallon tank would overload the pump.

    You should probably have a Pumptec or other device in the well pump circuit to protect the pump if the well from being pumped down too far.

    You would need a pump from the 2500 gallon tank to the pressure tank. I suspect that the Davey pump might be inadequate. I would have to see the curve for the pump.

    There would be another float switch in the tank to protect the Davey pump (or another) if the 2500 gallon tank runs out of water. I will refer to the Davey pump but it may not be adequate for the service.

    Your pressure tank would be supplied by the Davey pump or its replacement.

    You can connect a chlorinator to the well-pump circuit to add chlorine (diluted bleach) to the tank. That is a good idea because those tanks can be contaminated.

    The hydraulics would be:

    Well pump => 2500 gal tank => Davey pump => Pressure tank
    with the pressure switch on the pressure tank controlling the Davey pump.

    No valve between well pump and 2500 gallon tank. You will need a check valve on suction or discharge side of Davey pump to prevent backflow from the pressure tank.

    You already have a filter for the potable water. I would not add another. The iron will probably be oxidized in the black tank and you may get more iron precipitate in the filter.
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  4. Southern Man

    Southern Man DIY Hillbilly

    Jun 27, 2008
    North Carolina
    I recommend keeping the big tank vented (no pressure), filled after the pressure tank through the top and with an air gap, and kept hydraulically separate from the potable system. Turn the well pump on-off with a float switch (you’ll have to figure out how to coordinate this with the pressure switch – maybe an electric valve). Use a separate pump to get water out of the big tank.

    This way you don’t have to worry about contaminating your potable system or using chlorine, which can’t be good for your crops. Iron removal is also not recommended because you’re just trading salt for iron and that’s not good for crops, while iron is.

    The other advantage is that you could plumb the roof leaders into the tank along with an appropriate sized overflow and maybe take some load off your well. Of course you’d have to develop a strategy to keep the tank near empty so maybe that would defeat the purpose of having it in the first place. :eek:
  5. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    I should have included that the 2500 gallon plastic tank can't be pressurized. They are vented and must be vented.

    If you want to pump from the well to the pressure tank and put excess water into the large tank you could use a back-pressure regulator off the pressurized system and a float valve in the big tank. You still must manage the distribution of water to the two systems so you don't run yourself out of household water.
  6. valveman

    valveman Cary Austin Staff Member

    Mar 15, 2006
    Pump Controls Technician
    Lubbock, Texas
    First, you wouldn't need a booster pump if your well pump was sized properly.

    Second, a Davey Booster pump uses a so called "Hydroscan", which is an on demand system, (flow off and pressure on), not a pressure switch.

    Third, a storage tank will not help unless your booster pump is large enough to supply more flow.

    What is the model number and well depth for the submersible pump?

    What is the capacity of the Davey pump?

    What is the requirement of the irrigation system?
  7. gwrace

    gwrace New Member

    Aug 27, 2008
    The well pump is a 3 wire 1.5 HP Aeromotor A+20 series rated at 20GPM. It's down about 260 feet.

    Here is the link to the Davey Pump. It's a model BT20-30. Pump curve indicates max flow at 27GPM at 10PSI or 20GPM at 30PSI. It is an "on demand" pump and has worked well for us for over a year with the irrigation system.
    Last edited: Aug 29, 2008
  8. Gary Slusser

    Gary Slusser That's all folks!

    Aug 31, 2004
    Wherever I park the motorhome.
    If the well pump was sized correctly, and the pressure tank set up correctly, you wouldn't need the booster pump or anymore storage than the pressure tank. Especially if you used a CSV.

    You say pressure but it's not pressure you need, you need more gpm/volume. Or to cut back on the irrigation gpm used and stagger use IF the water in the well is being pulled down too far reducing pressure (keeping the pump running at much less pressure).

    You aren't very clear on the actual problem, or how many gpm the irrigation is using or for how long and how frequently.... etc.. So what exactly is happening that you install the Davey and how is it failing to solve the problems?

    The Davey can only move the gpm/volume of water that is delivered by the well pump. And as we see, it ain't working well and now you want 2500 gallons of stagnant water sitting in TX and to use it in the house too. Have you thought of any needed water treatment with that set up?
  9. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    I looked up the curve on the Aermotor A20+ 1.5 HP pump. Its suitability would depend on depth to water in your well. If you are pumping down to anywhere near the pump at 260 ft then the head is inadequate for good pressure service without the booster pump.

    With the booster pump you can pull 20 GPM from the well because you will be reducing the pressure at the top of the well to nearly zero. If the water is significantly above the pump you can get 25 GPM. Those are also the flows that you can put into the plastic tank.

    If the water in the well is 50 ft or so above the pump, then pumping from the tank with the Davey pump will give you WORSE performance than you are getting with the two pumps in series. That is because you will be losing some of the head available from the submersible pump.

    If you don't understand and analyze the details of the system you are trying to build you will be very disappointed in the performance.

    I'm an engineer and there is a process that engineers use to get it right the first time.

    The first step is to think about and establish the requirements. That is as simple as thinking about and writing down exactly what you want to accomplish. How much flow in GPM, and how much pressure. One of the requirements is the constraint of how much water the well will produce, from what depth of water in the well.

    The engineer then creates an idea of a how to accomplish that; and then analyzes how that concept will work. Will it really meet your requirements?

    I'm sure I don't know exactly what your concept is, but from my understanding of your description it appears that you are on the way to making it work less well than it does now.

    That is not to say that something like it can't be made to work. However, you would probably need a different booster pump to get satisfactory pressure from the water in the plastic tank. On the other hand, you could use your existing system and store "excess" water in the plastic tank. Then you would need another pump, with more capability than the Davey, to deliver that water to your irrigation system.

    The process is:
    Requirements=> Design=> Analysis=> Redesign if necessary=> Analysis to confirm dedsign=> Build.

    If you do that you will have a system that meets your requirements.

    If you skip those steps you are on the way to disappointment and $$expense$$ to make it right.
  10. gwrace

    gwrace New Member

    Aug 27, 2008
    Understand the process

    Believe me when I say I understand the planning process. I have degrees and certifications in Network Engineering and project mgmt and it's my full time job.

    I simply want to store excess water in the plastic tank to pick up the slack from the well. The Davey pump is currently out pumping the well while the irrigation system is running. Household water flow and pressure is fine.

    Since we are in south Texas we get the occasional drought. The tank would be a backup reserve to a dry or reduced capacity well. And yes I've thought about sanitation. The water flows from the well to a whole house filter that feeds a softener that feeds a whole house distiller.

    I had planed on using chlorine to sanitize the tank water.

    If it were up to me I'd choose to dump the well and septic system as both have been problematic. But the city refuses to run services to our neighborhood even though we are only just a few yards away from subdivisions that have full city services.
  11. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    Let's look at how it is working now.

    Well pump => Davey pump =>pressure tank.

    Pressure tank and Davey pump feed the irrigation.

    If you have a gauge on the suction side of the Davey pump, what is the pressure? I suspect that it is greater than ZERO pressure.

    If you don't have a reliable pressure gauge on the suction side of the Davey pump then you have no way of knowing what will happen if you try to pump out of plastic tank with the Davey pump.

    The table for the Davey pump says it will only do 10 GPM at 40 psi at zero lift. Zero lift is the condition that will exist when pumping from the plastic tank. Ten GPM is a lot less than you are saying you get now; so the well pump is giving you more pressure. I suspect that you are getting 10 to 20 psi at the suction of the Davey pump when it is connected to the well, compared to ZERO that you will get from the plastic tank.

    That is why I said you are likely to get WORSE performance pumping out of the tank than you are getting when the suction of the Davey is connected to the pipe directly from the well.

    If you are going to use water from the tank in your system then you need a pump that will raise it to the pressure you need for your system.

    You said you are using a 30/50 pressure switch setting. I suspect that is the maximum pressure for the Davey pump. You can't operate a system when the maximum pressure capability of the pump is the same as the shutoff pressure of the switch.

    If the Davey doesn't give you satisfactory pressure in the pressure tank when the pressure on the suction side of the pump is zero psi then the system won't work if the Davey is pumping from the plastic tank.

    You can store excess water in the 2500 gallon tank. You can disinfect it. But you can't use it unless you have a pump that will deliver adequate flow and pressure from a tank that provides ZERO pressure on the suction side of the pump.
  12. gwrace

    gwrace New Member

    Aug 27, 2008
    Thank you

    Thanks for all the replies. I have done some additonal research on pumps and the following have been recommended to me by a couple of different well pump contractors.

    This pump would be placed right next to the 3000 gallon water tank with zero lift and a flooded suction.

    The first recommendation was for a Jacuzzi now Franklin Electric RM2 series.
    1 HP model 1RM2-S. Cast Iron with Brass Impeller.

    The 2nd recommendation was for a Goulds J10S or J15S. Similar pump curves but Nylor impeller. Not sure about casing. (Cast Iron>)

    About $3-400 price difference between these models. Both should be able to deliver the required 20+gpm per the pump curves.

    All recommendations appreciated.

    Stephen Nordyke likes this.
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