Goulds: Check valve below the pitless not at tank?

Discussion in 'Pumps and Tanks Well Forum & Blog' started by craftech, Sep 5, 2008.

  1. craftech

    craftech New Member

    Messages:
    52
    I will be installing a new pump and I noticed that Goulds says that for installations with a captive air tank:

    "On installations with a pitless adapter the top check valve should be below the pitless adapter, not at the tank, as the discharge line should be pressurized back to the pitless."

    See page 6:

    http://www.goulds.com/pdf/IM096.pdf

    I have never heard that. Anyone know the reason for this?

    Thanks,

    John
    Last edited: Sep 5, 2008
  2. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    The only check valve you should have on a submersible pump system is the one on the pump itself. Another check valve anywhere else can cause a vacuum or negative pressure before the second check valve. If that second check valve is above ground, the potential of drawing in contaminates because of the vacuum conditions is probable. If the second check valve is below the pitless, on anywhere on the drop pipe, the potential of a water hammer event happening at each pump start is very real.

    Using a second check valve just in case the one on the pump fails is never a good idea. If the check on the pump fails, it must be replaced. Having a second check valve will only mask the problem of the first check valve, and cause water hammer and possible contamination in the process.

    Cycling the pump on and off is what destroys check valves and most other equipment in a pump system. The check valve slamming shut from a full open position when the pump is cycling repeatedly is the main cause of check valve failure. Using a Cycle Stop Valve on your pump system dramatically reduces the number of times your pump cycles, which will increase the life of the check valve and all other components in the system. The Cycle Stop Valve is also in the 1 GPM position, not fully open, when the pump shuts off. This means that the check valve is also only open to 1 GPM, which is only the width of a piece of paper, not fully open, when the pump shuts off. This means that the few times that the Cycle Stop Valve allows the pump to cycle, the check valve does a nice gentle close, which eliminates water hammer and check valve failure.
  3. Leaky Boot

    Leaky Boot New Member

    Messages:
    31
    line

    The line from the pitless to the tank runs underground in most cases. In case of a small leak in the pipes in your well and a small leak in the underground pipe and while the pump is not running you have a suction condition on the pipe underground and draw whatever cruddy water it's buried in right into the pipe leak spot. Then the pump kicks on and it goes into the tank.

    Not said very well----but that's one reason for keeping the buried pipe under pressure at all times. LB
  4. craftech

    craftech New Member

    Messages:
    52
    Thank you so much for the long response.

    Will that tell me (as Leaky Boot points out) if there is an underground leak between the pitless and the tank?

    With a CSV, is the system pressure in the Captive Air tank pressurized from the house out to the well and all 400 feet? IE: 420 feet of pressurized water between the pump and the tank each time it cycles? Not sure I get it yet?

    John
  5. craftech

    craftech New Member

    Messages:
    52
    I see. What about Valveman's post regarding using only the check valve on the top of the pump and no other check valves, but using a Cycle Stop Valve instead. Not sure I get it, but do you agree with that suggestion. I am good for roughly 4 GPM at 60 psi with the new pump I will install.

    Much appreciated:

    John
  6. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I agree, only one check valve. The one in the pump. Any other check valves is only asking for more problems. And like LB said, one in the house can allow contaminated water into the system.

    The CSV will reduce or eliminate water hammer which has nothing to do with check valves per say.

    bob...
  7. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    The CSV does not work like a check valve. It will let water go backwards through it as well as forwards. So when your pump shuts off, you will have the same pressure that is in the pressure tank, back through the CSV, all the way to the check valve on the pump. This keeps the underground line and the drop pipe pressurized at all times and prevents a vacuum or negative pressure in the line.

    If you close off a valve in the line going to the house, when the pump shuts off, you can tell if the pressure drops over time. If it does, then you have a leak before the pressure tank. It could be underground before the pitless, or in the well somewhere.

    A CSV would only reduce the flow to 1 GPM before the pump shuts off, making it easier on the check valve than if it slammed closed from a fully open position. Although, if you only have a 4 GPM pump, the check valve will not be fully open like it would be with a 20 GPM pump. So a CSV would not make much difference on how far the check valve is open when the pump shuts off, it would only reduce the number of times that this happens.

    Reducing or eliminating the water hammer does have to do with the check valve. It is the slamming of the check valve that causes water hammer, and also wears out the check valve.
  8. craftech

    craftech New Member

    Messages:
    52

    I see, so that would be a CSV150 for my application. Is that right? 4GPM at 60 psi. 40/60 system with no check valves in the line and a CSV before the tank somewhere.

    Shutoff where the Check Valve is now installed (right where the water line enters the house)?

    John
  9. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    Yes that would be the right valve but, again the CSV will not help much with a 4 GPM pump.

    The cut off to check for a leak needs to be after the pressure tank and before the house.
  10. craftech

    craftech New Member

    Messages:
    52
    I have several of them. One after the pressure tank and one after the Whole House Filter that follows it.

    I thought you meant a shutoff entering the house between the pitless and the pressure tank.

    It seems that when I pull up the pump and replace it, I should just

    1. Remove all the check valves on the poly pipe.

    2. Re-couple the poly pipe where the check valves were.

    3. Get rid of the check valve where the line enters the house, and be done with it.


    Really appreciate this kind of help Valveman.

    Regards,

    John
    Last edited: Sep 5, 2008
  11. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,260
    Location:
    Land of Cheese
    Why

    If this is such a problem why is is normal for drillers and pump installers to install a check valves every so many feet along the drop pipe?

    Even a recent article in Well Driller Magazine prescribed using multiple check valves as a correct installation!
  12. Gary Slusser

    Gary Slusser That's all folks!

    Because they like selling things that aren't needed and can cause other problems that they are called out to fix? I think so.
  13. masterpumpman

    masterpumpman New Member

    Messages:
    729
    Location:
    Virginia Beach, VA
    OK, valveman?

    cacher_chick
    Why
    If this is such a problem why is it normal for drillers and pump installers to install a check valves every so many feet along the drop pipe?

    Even a recent article in Well Driller Magazine prescribed using multiple check valves as a correct installation!

    Please answer cacher_chick's "Why" question.

    I need that explanied to me as well.
  14. craftech

    craftech New Member

    Messages:
    52
    Could they have been talking about wells with plenty of output and plenty of water pressure instead of the low yield wells that a lot of people like myself have?

    John
  15. Gary Slusser

    Gary Slusser That's all folks!

    Your pump creates pressure, not the well.

    Each check valve usually needs 5 psi to open it. All submersible pumps have a check valve in the outlet or an external one on the outlet. I don't know of any good reason for another one anywhere and I have read all about adding one every hundred feet etc.. To add one, you need two fittings and they also have a pressure loss. And all submersible pumps have no problem with only its check valve; and that's to 500' deep.

    Because they like selling things that aren't needed and can cause other problems that they are called out to fix.
  16. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    I think it is just one of those things that works on paper, and not so good in reality. You don't want water to go backwards when the pump shuts off, so if one check valve is a good thing, then a hundred check valves would be better.

    However, the more check valves you have the more friction loss you have, just as Gary described. A bigger pump is needed if you have much friction loss. Other than that, you would still think an extra check valve or two would still be a good idea for backup.

    Many times, multiple check valves do work OK when everything is new and working perfectly. The problem comes when any check valve leaks a little bit, or doesn't close quite as fast as the check valve above it. Then a negative pressure is created below the top check valve.

    If the top check valve is above ground, the vacuum can draw contaminates into the line. No matter if the top check valve is above ground or in the drop pipe, the negative pressure will allow the pump to start to the right of it's curve. (In other words "wide open") The pressure above the pump will change from negative pressure to positive pressure in a fraction of a second. The effect is, the column of water below the top check will "punch" the top check. This is much like a Boxer "punching" you in the face. It creates a shock wave that travels throughout the water lines. At every outlet valve, elbow, tee, and dead end in the pipe, the shock wave turns into water hammer. Water hammer causes everything in the pipe system to experience pressure 10 times what you see on the gauge. On larger pumps it usually causes the pressure switch to bounce on and off like a telegraph.

    You can remove the upper check valve when they start causing problems, or you can install only one check valve at the pump and not have the problems.

    I have installed systems as deep as 2200' with only one check valve. You just need a good check valve, and to start and stop the pump at almost deadhead pressure conditions.
  17. craftech

    craftech New Member

    Messages:
    52
    That's a really clear and detailed explanation. Thank you (and the others) for taking the time to help me with these problems. Very much appreciated.

    John
  18. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I think it's a reason that some people should not be allowed to write these books, or instruction manuals when they really don't have a clue as to what goes on in the real world.

    bob...
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