Shared Well - Multiple Tanks - Inconsistant Pressure

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by SDSolutions, Jun 20, 2019.

  1. SDSolutions

    SDSolutions New Member

    Joined:
    Jun 20, 2019
    Location:
    Minnesota
    I have a situation and I am trying to reverse engineer and understand it. I have talked to some local plumbers (who are not well experts) and have received differing answers. Reading these forums, I have learned so much, I wanted your collective expertise. Thank you for listening, and I am trying to share the whole picture.

    I have been in my home just a few years. I am on a shared well, and recently had our Pressure Tank Replaced due to a leak. The plumber who came out wasn't the most knowledgable on wells, but could connect pipes just fine. After he left I started analzying this shared well and talked to the neighbors. We all experience sediment in the water, relatively low pressure, and low volume (when trying to run pressure washers, etc). If I had my own well, I'd be able to fix that. On this shared well, I'm inexperienced Here's the situation I am observing:

    We have a well 160' deep with a pump less than 10 years old (fully replaced entire well housing in 2009, not just the pump). It is a 5 house shared well in parallel with 3/4 mains to every house, and every house has a 32 gallon bladder pressure tank. We also believe there is a 600 gallon buried water tank that was likely installed in the 80's (according to hearsay from previous owners) Of the 5 pressure tanks, 3 are 10-20 years old, 2 are less than a year old (including mine). The well pump has a single pressure switch at the pump itself, and there are no check valves in any houses, only on the well pump

    The plumber could not find the curb stop shutoff valve to my house (I later found it buried), and the house main shutoff inside is installed after the pressure tank. Therefore the plumbers shut off the well and we drained the entire system to replace the tank. They shutoff a valve that they thought may go to my house, but I now believe that valve shutoff the 600 gallon buried tank. That draining process only took about 20 minutes to flush out the 3/4 garden hose with alot of air and sediment coming out at the end.

    The Pressure switch is set 30-50, and the plumber left my pressure tank set at 42, which resulted in no water being filled into my tank. the plumber was smart enough to install an in-house shutoff before the pressure tank so I could Isolate and drain just my house (or shut it off in the case of a future leak in the tank). I proceeded to drain the house pressure and set the pressure tank to 28psi empty. I then re-pressurized the house and confirmed the tank was now providing me pressure and volume (isolated).

    I went to the well with my garden hose (3/4 pipe from the main to the garden hose, 3/4 hose), a 5 Galon bucket, and a stopwatch to test the system. I first ran the hose until the well pump kicked it (30psi). The pump ran for 30 seconds, pressurizing up to 50psi, then shutting off. The pressure then proceeded to drop from 50psi to 40psi slowly, in less than a minute. It then stabilized at 40psi and stayed there constantly (monitored for about 30 minutes with no neighbors home and no one running water). I then turned on the garden hose and filled the bucket. Flow rate was about 5GPM, and I drained about 25 Gallons of water out of my hose before it hit 30 PSI and the pump kicked in. Same sequence followed, pressurize to 50, shut off, drop to 40, stabalize.

    I spoke to the neighbor who recently also got a new pressure tank, and sure enough the plumber failed to set his pressure to the proper 28psi for our well, so we adjusted his pressure as well. I repeated the test above and had everything the same, but got another 7-8 gallons of water usage before the pump kicked in. I expected this based on his pressure tank now helping the system. I am going to be working with the other neighbors to ensure their pressure tanks are not waterlogged, but I wanted to better understand the system before I do.

    My observations have lead me to some conclusions. Please tell me if I am wrong.
    1) The Buried tank is either disconnected, doing nothing, or completely useless. 5 Parallel pressure tanks at 32 gallons each should supply us with 30-40 gallons of water before the pump has to kick in.
    2) Possibly one of the other 3 pressure tanks is water logged or over pressurized. We should be getting 40 gallons with 5 heathy tanks, and we are only at 32.
    3) we all would benefit from the pressure switch increased to 40-60, but I want to ensure all pressure tanks are healthy before I do that. I also am worried about the immediate drop to 40psi and causing a constant short cycle. Don't want my idea to be blamed for a neighbors tank leaking/bursting, or skyrocketing electrical costs, or a failed pump.

    What I don't know that I would appreciate your expertise...
    1) Why is the system dropping from 50 to 40 PSI immediately. A bad check valve in the well and I would expect it to constantly cycle.
    2) The well pump only takes 30 seconds to re-pressurize the system with 30 gallons+ of water. Does that mean our well is pumping at about 60 gallons per minute? With that rate, we should not have a volume problem unless there is something else happening, or if the 3/4 pipe to the houses is impeded somehow.
    3) What else to I need to test to get better answers?

    Thanks!
     
  2. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    This is a good example of why you shouldn't put additional pressure tank a distance away from the pressure switch. There is apparently 10 PSI of friction loss between the well head and the multiple pressure tanks. When the pump is running there is 10 PSI more pressure at the well head than at the tanks. So, when the pump shuts off at 50, the pressure will equalize with the pressure in the tanks down to 40. The only tank(s) in the system need to be close to the pressure switch at the well head.

    This means you are not getting the draw down from the distant tanks as you think you are. It also probably means your buried tank is still working somewhat to get the draw down you are measuring. So there is really no way to tell if it is a 60 GPM pump or what, until you figure out for sure how much draw down the tanks are holding, or until you do a bucket test from a large open line from the well.

    The pump only running 30 seconds is not good. The pressure fluctuations from all the unequal tanks would be aggravating.

    Adding a Cycle Stop Valve to the pump would have many advantages. The homeowners would love the strong constant pressure compared to the wide pressure variations you are seeing now. The CSV would be filling the tanks at 1 GPM instead of full pump volume. This will eliminate the friction loss in the lines, and all the tanks would fill at the same rate. You also would not need so many tanks as one 86 gallon size tank would take care of all the houses. But you could leave the tanks at all the houses if you want, and the combined total would only need to be 80 gallons or so. The problem with too large or too many tanks is that you have to wait for them to drain as the pressure decreases from 50 all the way to 30 before the pump comes on. Once the pump comes on the CSV will start providing a constant 45 PSI to all the houses. The constant 45 will be so much stronger pressure that you will hate waiting on those tanks to drain and the pump to start.

    Here is a graphic of multiple houses you can play with.
    https://cyclestopvalves.com/pages/municipal-one-well-system
     
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  4. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Your first need might be to find a lawyer to make sure that your good intentions and hard work don't get punished due to some negative outcome.

    With remote pressure tanks, I think they would do better with a spring-loaded check valve in the line to them. Where the pressure switch is should not have a check valve between it and the tank. The remote tanks would cut out sudden pressure changes due to usage at other houses. The check valves would cost about 1 or 2 PSI however.

    I would consider upsizing the pressure tank at the pressure switch unless you decide to use a CSV.

    Is your pump able to work with a higher pressure pressure switch? You can test for that. You could measure the dead head presure, and subtract a margin... maybe 10 psi. You want to make darned sure that there is margin so that the pump is able to shut off reliably.

    I am not a pro.
     
  5. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    I wouldn't add any more check valves. Just make sure the one on the pump is good.
     
    Reach4 likes this.
  6. SDSolutions

    SDSolutions New Member

    Joined:
    Jun 20, 2019
    Location:
    Minnesota
    Note: we are in Minnesota. Frost line goes down almost 3 feet. All pressure tanks are either buried deep or are in people's houses. Can you easily install a CSV undeground? Or would we install a CSV in every home at every pressure tank?
     
  7. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    CSV would go before the pressure switch and before the pipe branches to any other houses.

    I expect the frostline is deeper than that, even in the tropics of MN.
     
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