well water, underground plastic tank...can it be pressurized?

Discussion in 'Pumps and Tanks Well Forum & Blog' started by Dolphin, Dec 31, 2012.

  1. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    Hi all, great forum... I have just taken over a property with a new well system. It services 4 residential properties, just being finished. I have general plumbing knowledge, but never worked on a well system...
    I was trying to grasp the well design...I think its improperly controlled and plumbed. Here is the set-up...
    Well pump feeds above ground in well house via 2" PVC pipe.... it feeds four 60 gallon pressurized bladder tanks (which are plumbed to act a single unit)....
    in addition, this 2" PVC feed goes down into the underground storage tank, about 1700 gallons, it appeared a poly tank when I saw it installed. Surely not metal.
    There is an additional water pump, which pulls water up from the under ground storage tank and discharges into the bladder tank loop, which in turn, pressurizes the underground storage tank. The check valves all seem to be in the right place.

    A few questions....

    1) Assuming I do not run the above ground pump (it could be there for fast fill of water trucks).....the way the system is controlled now, the well pump is controlled by a pressure switch on the bladder tank loop....set at about 50 lbs. However, this well water feed also fills the underground poly storage tank.... so the underground storage tank will have the same pressure as the bladder tank loop. Which forces the underground storage tanks "overflow" to release water by the well house. My initial question is... are underground poly tanks meant to be pressurized ? I would think, NO! ??

    2) Assuming I have the above correct.... I would think the most sensible control scheme would be..... the well pump should be controlled by a float switch in the underground storage tank. (there is a wire coming up from the storage tank which must be a float switch) The well pumps sole purpose should be to keep the underground storage tank full, till the float switch engages, but never under pressure. I would have to re plumb to accomplish this.

    3) The above ground pump near the bladder tanks should be controlled by a pressure switch on the bladder tank loop. It's sole purpose should be to pressurize the bladder tanks with water up to 50 lbs. of pressure.

    In other words, two separate control loops, which function independent of each other. Is this the "ideal" control scenario? Or can a single well pump pressurize the bladder tank, as well as the underground storage tank? As I see no way the underground poly storage tank won't constantly be pressurized every time the well pump comes on. Which is creating a lot of overflow, and some some water percolating up through the earth above the storage tank, as the overflow drain pipe size was undersized vs. the well pumps capacity. I am confused why it was plumbed and controlled by this method, seems bizarre to me... this was an experienced well driller which is why I am thinking I am missing something.

    Any input would be greatly appreciated, TYIA
  2. valveman

    valveman Moderator Staff Member

    Messages:
    4,459
    Location:
    Lubbock, Texas
    The 1700 gallon storage tank cannot be pressurized. There is an additional pump in the storage tank that pressurizes the water in to the bladder tank loop. With the well pump working from a pressure switch, there should be a float valve or a float switch operating an electric valve to fill the storage tank. If the storage tank is overflowing, then the float valve or float switch is not working or not set at the proper level.

    There are several ways to set up the control scenario for a system like this. I would probably set the pressure switch on the well pump to operate at a higher pressure than the booster pump. Ie; well pump at 40/60 and the booster pump at 30/50. I would also have the electric tank fill valve tied into the pressure switch for the booster pump. When the well pump cannot satisfy the demand by itself, the booster pump comes on at 30 PSI. I would tie the booster pump in with the float switch for the electric valve, so the storage tank stops filling while the booster pump is running. This will give you the combined total volume of the well pump plus the booster pump for peak demands.

    When the peak demand is satisfied, the well pump will be able to increase the pressure to 50 PSI, which shuts off the booster pump and opens the electric valve to refill the storage tank. When the storage tank is full the float switch closes the electric valve. Then when there is no more demand, the well pump increases the pressure to 60, and the well pump is also shut off.
  3. VAWellDriller

    VAWellDriller Member

    Messages:
    171
    Location:
    Richmond, VA
    What is the capacity of the well pump? Since it's only 4 houses, if your well yield and pump is good for anything over 15 - 20 gallons / minute, you can easily just do away with the 1700 gallon tank totally; install 1 pressure tank and a cycle stop valve. I build a lot of systems like this for anywhere between 2 and 100 houses. On just a few houses, I use the well pump, small pressure tank, and a CSV. When I get over 12 connections, they are considered public water systems governed by our state health department. There are more regs on water storage, peak flow, etc. Normally systems are engineered to pump directly to nonpressurized storage with the well pump and then have two centrifugal pumps (with two seperate pressure switches), drawing from the storage to pressurize a tank and the system. The well pump is controlled by BW liquid level controls, and but it is also plumbed and valved so that if there is a problem with either the booster pumps or the storage tank, you can open a valve and turn a switch and have the well pump pressurize the system and run off one of the pressure switches. If you have the capacity of the well, I would just simplify the whole system. If you have to use the underground tank, you need to re-plumb it so it's not pressurized.
  4. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    thanks guys for sharing your knowledge and thoughts.... Yes, the water demand is very low, it will prob. remain that way for the foreseeable future.... as VAWD suggests in his post...the four 60 gallon pressurized tanks is more than sufficient for the next several years. I do NOT have any specs on the well pump, the installer left NOTHING. However, it seems the well pump builds up pressure in the four tanks sufficiently...I will confirm this.

    1) What is an acceptable period of time for these tanks to reach pressure? 5-10 minutes?

    2) I can close a manual valve feeding the underground storage tank. Now the well pumps role will be to ONLY pressurize the four 60 gallon bladder tanks, which feed the properties. This raises one other question.....
    With the pressurized tanks fully charged, I assume there needs to be a check valve to PREVENT water from back feeding down the well. I don't see a check valve above ground to prevent this... or maybe a check valve system is built into the well pump below ground?

    3) That underground storage tank is full... is that OK? Should I install a valve that can gravity pour some bleach down into storage tank occasionally? The summers get HOT, and while the tank is underground, it only takes a small amount of growth in the above ground piping to turn the storage tank full of growth, I would think......or should I attempt to drain the storage tank?

    Valveman, your strategy makes perfect sense. And currently, there is NO electric valve that shuts off flow to the storage tank via a flow switch..... this represents the overflow condition. thx for sharing that.... makes perfect sense. For now, if the well pump + pressurized tanks is more than sufficient, it makes sense to remove the storage tank from the equation. In the future, when demand increases, I can install an electric valve to prevent storage tank overfill and add a 2nd pressure switch to control the booster pump. Its nice to know the future control strategy.... much appreciated.
    TYIA
  5. valveman

    valveman Moderator Staff Member

    Messages:
    4,459
    Location:
    Lubbock, Texas
    It all depends on the size of the well pump. If the well pump will produce the volume and pressure needed, then I would drain and disconnect the storage tank and booster pump.
  6. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    Valveman, I fully agree.... I am pretty confident the well pump is sufficient... I will investigate that in the next day or two...

    Assuming it is, should there be a check valve on the outlet side of the well pump, to prevent pressurized water going back down the well, when the well pump is off of course.... or do all modern well pumps have back flow prevention built into them?
  7. valveman

    valveman Moderator Staff Member

    Messages:
    4,459
    Location:
    Lubbock, Texas
    There has to be a check valve down the well on the pump, and that is the only check valve needed.
  8. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    OK, I assumed so, but u know what happens when one ASSumes :)
    been burnt too many times with assumptions
    Thx for confirmation...
  9. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    Spent some time at the well house..... a few more questions ...
    The well pump pressurizes the 4 bladder tanks in about 5 minutes.... more than acceptable. I think for now, that will represent the "total system" in use....
    Now, the problems...
    As suggested above, its prob. best to empty the underground 1700 gallon storage tank and poor some bleach down the tank, as I am sure I can't remove 100% of the water....
    I fill the underground storage tank....it starts to overflow.... I know its full... (as mentioned above, the installer has no auto cut-off on the tank fill line)
    I turn on the booster pump, which pulls from the underground storage tank. It produces about the same water flow as the well pump...is this normal? My guess, 12-15 gpm.
    The pump runs for about 10 minutes, and then water flow stops, the pump starts pulling air..... the underground storage is 1700 gallons.... ??
    The only logical conclusion I have for this is..... there are two pipes coming up from the storage tank....
    I would think, the fill pipe should run just below the top of the tank, and the suction pipe (to booster pump) should run close to the bottom of the tank.... I am assuming this is how the storage tanks are normally plumbed?.
    If so, I think the installer mistakenly connected the "tank fill" pipe to the booster pump, hence why the pump runs dry long before the storage tank is empty. make sense??
    TYIA for all your assistance....
    Last edited: Jan 6, 2013
  10. valveman

    valveman Moderator Staff Member

    Messages:
    4,459
    Location:
    Lubbock, Texas
    That would make sense. What doesn't make sense is why the booster pump would pump into the same line that feeds the storage tank from the well pump.
  11. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    Valveman.... agreed.... my guess is.... the booster pump was a means to increase flow rate to a large fill hose, 3" diameter, that filled a water truck. (no longer used) But its so under-sized, it does not serve much benefit even for that purpose.

    Although my game plan is worked out, thx to help on this list.... I still have one mystery, I have not solved .... (always hard to solve these mysteries when part of the system is buried, i.e. not visible!) .....

    the two pipes come up from the underground storage into the well house...... obviously one is the fill, the other is discharge....in addition, there is one 110v two conductor cable coming up with the pipes..... the obvious thought is, this is the float switch wire. He has this wired into the pressure switch. I have no wiring diagram on the pressure switch...it has two sets of terminals, 230V and 110V. of course the 2 pumps are on the 230V circuit (with the booster pump having a toggle switch near it for final control) But why is the 110V wire into this switch? I assume the pressure switch completes the circuit on the two terminals when pressure goes below 40lbs, and opens the circuits above 60lbs (from testing this is where the pressure on/off values).... unless the 110V terminals act as control source, which they must be hot for this to occur..... (which I doubt), then this 110V line (most likely the a float switch) should NEVER be wired into this pressure switch. Am I missing something? Don't need to use it now, but would sure like some confirmation on my thoughts..... TYIA again....
  12. valveman

    valveman Moderator Staff Member

    Messages:
    4,459
    Location:
    Lubbock, Texas
    The two wires needed to start a pump can be connected to a pressure switch or a float switch. This depends on if they are filling a pressure tank or a ground storage tank.
  13. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    OK, worked all day re plumbing, and yes, the installer reversed the "fill" and "suction" pipes in the well house.... emptied all 1700 gallons in the underground storage tank, into water truck.... my suspicion was right about that ridiculous error.....
    So the two wires coming up from the underground storage tank ..... I would think, these MUST be a float switch, as what would electrical cable be doing in the tank, other than a float switch? I think this too is mistakenly wired to the pressure switch.... the pressure switch "appears" to only "makes" the connection on the 110V and 230V terminals. When pressure falls below a certain level, it closes both circuits? So why would you "switch" a non powered float cable? No harm being done, but it serves no purpose either. ?? Its so bizzare anyone could do this....but this job has not stop surprising me....


    any input would be helpful..... on that cable....

    here is my prelim. game plan on this.... I would appreciate any input, advising me if this is the prudent course .....

    remove the 110V wires from the pressure switch (switch is located on the bladder tank loop)...... The system works fine with the booster pump "out of play".... i.e. well pump charges all 4 bladder tanks, and turns on and off based on the pressure in the loop. I am sure the 110 V cable coming up from the storage tank, are NOT live...cause there is no power going under ground. With the cable removed from the pressure switch, put a continuity meter on the two conductors when the tank is empty.... hopefully there will be no continuity, float switch is open, which makes sense, as tank is empty.... then, fill the underground storage tank, as the tank fills, if continuity meter goes "off".... confirming these two conductors are from a float switch, which are of course, not powered. If this is the case (I am hoping).... I remove the 110V cable from the pressure switch, introduce 110V power on one leg, and have it engage a "tank fill" valve on the 1 1/4" PVC tank fill pipe. This will assure no one will ever again pressurize that underground tank, which occurs easily if you have the wrong valves open. This should be there regardless if and when we plan to fill the storage tank in the future.... for now, that vavle will be open as the storage tank is empty, so we use the manual valve next to it, to prevent the pressurized bladder loop from filling the underground storage.... and for now, the booster pump remains "out of play" till the time comes when we need the underground storage, then we dedicate the booster pump to the pressurized bladder loop, and the well pump will only turn on/off based on the float switch...

    any thoughts or comments would be appreciated....
    TYIA guys.... much appreciated.....
  14. valveman

    valveman Moderator Staff Member

    Messages:
    4,459
    Location:
    Lubbock, Texas
    I would think the two wires coming up in the storage tank are to control the well pump. So I would also think these are the wires that need to be attached to the pressure switch, as you are now using the well pump directly into the bladder tanks and house line.

    Just take the handle off any manual valve you don’t want someone messing with.
  15. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    Maybe I am confused on the role of the pressure switch..... the Press switch is on the bladder loop..... it turns the well pump on/off...the well pump (as currently valved) pressurizes this bladder loop. All works well.

    Currently, as mentioned, the underground storage will remain empty, no need for that capacity. The objective of the well pump is to pressurize the bladder loop, which is exactly what the pressure switch is doing.

    Lets assume the black cable coming from the storage tank is from a float switch. Why would I want a pressure switch to open / close a float circuit? Can you explain how these pressure switches work? I assume they close both the 230V and 110V terminals below 40psi and open both terminals over 60 psi... right?
  16. cableguy

    cableguy New Member

    Messages:
    3
    Location:
    Northern Idaho
    Gentlemen:
    I have seen more than one buried plastic tank float out of the ground with high groundwater.
    Also, they may have a tendency to collapse if left empty.
    My 2 cents.
  17. Dolphin

    Dolphin New Member

    Messages:
    19
    Location:
    NV
    Yikes! I did not think about the tank collapsing..... would you leave an underground tank empty?
    I hear ya on the float, I have can't be sure till I test it.... would you agree with my test procedure....also, typically, what type of floats are used in these underground storage tanks?
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