The check valve discussion.

Discussion in 'Pumps and Tanks Well Forum & Blog' started by speedbump, Nov 28, 2005.

  1. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Shack,

    So they recommend putting it up 20 to 40 feet. That's weird. It would seem to me if you install a check valve above a pump 20, 40 feet, the pump shuts off, a vacuum is created by the water falling down to the water level or as far as it can. Then on comes the power and wham, the water column takes off at the speed of sound smacks the poppet and bang goes the water hammer. I'm not sure just how many of those whams the check valve poppet can take.

    bob...
  2. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    That’s not exactly what will happen though. I though that for a while, too. If the water level is above the check valve the hydrostatic pressure will keep the water from exiting the last two joints of pipe. The other common the pump supplier made was that they also recommend the check valve be placed at the SWL. I think this is less advisable. A small change in static water level would cause the effect you spoke of.

    Now that I think about it, I believe that Crown Pump (now Sulzer) has also recommended placing the check valve one to two joints above the pump.

    Normally this placement is a real pain the butt, especially since we are using certalok drop pipe a lot. However, I believe there are now checks that will replace a certalok coupler. It still isn’t as simple as thread the mpt x fpt check right into the discharge.

    Moderator: Can we move the other pertinent discussion to this thread?
  3. almostdone

    almostdone New Member

    Messages:
    8
    Speedbump,

    I have a question on your comment that a check valve by the bladder tank was not correct. I just moved into a house that has a xtrol pressure tank and just upstream from it before the plastic supply pipe enters the house - a flomatic check valve.

    I wondered about it because I know that the well pump is more than 100 ft down, so as you mentioned in your comment on this thread the check valve just creates a huge area of vacuum as the water level drops to the pump. But if I understand you and Shack correctly, submersible pumps are installed with a check valve directly above them.

    So, it this check valve needed. I understand that houses hooked up to municipal water need a check valve inside the house to prevent contamination if siphoning occurs. Should I take this one out?

    Thanks for your comments.

    DM
  4. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    It’s not a check valve on municipal systems. It’s a back flow preventer! LOL
  5. almostdone

    almostdone New Member

    Messages:
    8
    OK, so I'm not on town water, so do I need this backflow-preventing check valve? :) It does alert me that the pump is running by rattling nicely, but speedbump said "Having a check valve at a bladder tank is a no no anyway." I'm wondering why?

    DM
  6. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    In the Cincinnati/ Dayton area we use a Watts #7 double check valve on residences not a back flow preventer on municiple systems. Back flow preventers are required on Comercial/Industrial buildings. I have never seen a backflow preventer in a residential application.
  7. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    Sorry, it was a joke.

    Anyway we should get back to the check valve/bladder tank discussion. I could be wrong but I think that he meant on the tank inlet. One way the check would never let any water out of the tank and the other way it would never let any water in. Either way it would defeat the purpose of the tank.

    If you have a check in the main service between the pump and the tank tee, I don’t know that it would be all bad or entirely good either. The problem would be that you would not be able to have a hydrant or anything like that between the well and the check valve. When the hydrant was opened the pressure would not drop at the pressure switch and the pump would not receive an on command. You hydrant would not get any water.

    I don’t know if these are the correct answers, but they are my thoughts.
    ld get back to the check vavle/bladder tank discussion.
  8. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    Just for the sake of some lively argument see the following link:

    watts #7

    Note the title of the page and the description of the product.
  9. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    Okay, I just got a phone call from our pump supplier. Part of the reason that they recommend placing the check valve up is the “that’s what daddy used to do and his daddy and his . . .†rational. They say that Layne recommended the check valves be placed in such a position and have continued to recommend that throughout the years.

    The other rational they used was from a friction and minor loss point of view. The claim is that if the water flow is allowed to straighten out in a couple of lengths of pipe there is less friction loss in the check valve. I suppose laminar flow through a check might indeed have less friction loss than the turbulent flow directly after the pump.

    I hope that I was able to explain this well enough.
  10. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Actually my reasoning for not having a check valve are all the ones above plus the fact that with or without a back flow preventer a leak in the pressure line could allow contaminated water into the supply lines anywhere from the pump to the house. By the way, all pumps I am aware of for domestic use up to 1.5hp have built in check valves.

    To explain what I mean, let's say there is a pinhole in the pipe from the well to the house. It has been raining and the gardener (like we all have Gardner's) has just put some pretty heavy fertilizer on the grass. The well driller that installed the sub, wasn't feeling real good the day he installed the system and didn't tighten the joints in the pipe the pump is hanging from. So there is a minor leak in the droppipe. While that water is oozing from the loose joints in the droppipe, water and fertilizer is being sucked into the horizontal underground pipe that has the pinhole. You turn the water on to bathe little Suzie and the pump has to come on to keep up with demand, the fertilizer and rain water are now pushed into the house because that check valve at the tank wouldn't let that line stay pressurized like it should be. Little Suzie is now a mutant living with Godzilla. Well you get the idea.

    bob...
  11. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    Not only is little Susie a mutant, but the neighbors will be after the contaminated water starts to leak into the aquifer from the loose drop pipe joints. Now even the neighbors have a five legged dog.
  12. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    OK you got me for a second :) Watts #7 U2-2 not 007

    is listed a backflow preventer by Watts but is a check valve as opposed to the typical type of back flow shown in the Watts #7 photo above. In our jurisdiction they differentiate between the two. The #7 U2-2 is considered a check valve and never referred to as a backflow preventer. Technically it can stop backflow.
    Last edited: Nov 29, 2005
  13. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    Six one way, half a dozen the other?

    I really don’t know the difference. Do back flow preventers have two checks and checks are just checks?
  14. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I'm no expert on backflow, but I think it's a bunch of false security IMO.

    The backflows are non spring loaded if I'm not mistaken and it takes pressure to hold them closed.

    Here in Florida they are required for all county water hookups, they put them near sidewalks, in front yards, just about anywhere you wouldn't want them. They have to be installed on all irrigation wells and I imagine soon enough on all domestic wells. They look like crap and for my money probably don't work anyway. Ever seen 10 feet of water over what used to be a subdivision. It's called a hurricane and backflow preventers don't stop hurricanes. If they aren't above the water line, they don't do a bit of good.

    Ask the people in New Orleans if their water was kept safe by backflow preventers.

    bob...
  15. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    I am no expert on this but a check valve closes when the flow of water stops. I am not sure about typical back flow preventers. I do know they trip under the right circumstances and need to be reset and they do have springs. I have installed them and rebuilt them but am not certified to do backflow testing and am not sure exactly how they work. I once had one bad right out of the box. It wouldn't stop dripping. It ended up being a brass shaving caught under one of the seats/seals. Here they are required to be tested once a year.
  16. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I believe testing is a requirement here too. Good racket for someone.

    The irrigation back flow preventers I'm familiar with don't have springs. When water flow and pressure stops, the poppet drops breaking the vacuum. When water flow starts the poppet is slammed shut for the duration. The other ones, I have to go with your experience because I have none other than I know they hurt when you hit one with your shin bone.

    bob...
  17. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    Here they get anywhere from $125.00-$175.00 for about 15 min. work. More if something needs to be replaced.
  18. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Where does an old fart get a certification to check and repair these brass wonders????
  19. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    Location:
    Cave Creek, Arizona
    check valve

    One of the first things to clear up is that when the pump stops the water does not "drop down to the water level in the well", at least not unless you have a leak or vacuum breaker on it that would allow air to enter the pipe and thus permit the water to drop. (If it did that then everytime the pump started you would have to expel the air in the pipe when you opened a faucet.) Otherwise the pipe stays full of water and the pressure increases linearly as the pump spools up to full speed and pressure. Therefore there is no "bang" when the check valve opens. In fact it will not open until the pressure in the pump pipe exceeds the system's pressure and then it will merely swing open, "gently".
  20. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I disagree HJ, if the droppipe has no leaks what so ever, there is no check valve in the pump or anywhere in the droppipe but there is one at the top of the well to hold the pressurized side of the system there. The water level is lets say 100 feet. The pump shuts off, what is going to hold that water up in that column of droppipe. I say there will be a vacuum created from the top of the pipe down to around the theoretical 32 feet. If the water level in the well is say 15 feet, then the water can drop to that depth or somewhere in between depending on the physics that I can not explain.

    Make sense?

    bob...
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