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Thread: Pump short cycles

  1. #1
    DIY Junior Member jbfjr's Avatar
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    Default Pump short cycles

    I have a jet pump with an 80 gallon pressure tank, no bladder. The feedback device is all metal (at my other house it is clear plastic). It appears to have a slight leak on the feedback device since there is a lot of minerals and rust on it.

    The pump doesn't seem to be acting right, at least in comparison with the similar setup at our other house; when the water is turned on, in just a few seconds the pump kicks on but only runs for about 8 seconds. This repeats over and over until the usage is stopped. I tried to drain the tank (thinking it was waterlogged) but it didn't change anything. However, I'm not sure how much of the tank I was able to drain. The flow rate seems to be fine, of course the pressure rises and falls each time the pump cycles.

  2. #2
    DIYer, not in the trades LLigetfa's Avatar
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    I have no idea what you mean by a feedback device. How does air normally get added to the tank? Draining the tank is not how to add air. Even if you managed to drain it completely and got it to be full of air, it would not be enough air once compressed. Some folk use an air compressor to top up the air.

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    DIY Junior Member jbfjr's Avatar
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    I used the term "feedback device" because I don't know the plumbing term. It's mounted on the side of the tank and has a tube that goes back to the pump/motor assembly, so I assume it tells the motor/pump when to turn on or off.

    How is the best way to get air into the tank once I drain it? There's a plug on the top of the tank, could I put a fitting on there?

    Thanks for the help,
    John F.

  4. #4
    DIYer, not in the trades LLigetfa's Avatar
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    It sounds like an air volume control to me. Obviously it's not working.

    http://www.grainger.com/Grainger/ite...5&cm_vc=HPPVZ3
    Last edited by LLigetfa; 12-14-2011 at 08:41 PM.

  5. #5
    In the Trades Texas Wellman's Avatar
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    You have an air volume control, probably AV-80 or AV-45. When they work, they are great. When they don't work, they are a PITA.

  6. #6
    DIY Junior Member jbfjr's Avatar
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    Default Pump short cycles

    Thanks, guys. The volume control I have looks like the Brady AV100: http://store.waterpumpsupply.com/120galtaneca.html

    I'll try replacing it. The one I have at the other place is clear plastic with a float ball. It seems to work OK but is more susceptible to freezing and breaking.

    Thanks again,
    John F.
    Needville, TX

  7. #7
    Jack of all trades DonL's Avatar
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    I have found that the best way to fully drain that type of tank is to kill power to the pump and Remove the air volume control then open the output and let it drain until the water stops completely.

    I removed my AV100 because I got tired of it not working or lasting very long.

    I put a plug in its place, and just remove the plug and drain the tank every 4 months or so.
    That also lets me flush the tank. I do not add any air. The plug just needs to be installed before turning the pump back on.


    I found that the Air Volume controls do not work very well or long. They were a PITA for me.
    Theory only works perfect in a vacuum.

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  8. #8
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by DonL View Post
    I do not add any air.
    That under-utilizes the size of tank and will not give you the best drawdown. It is marginal at best and just gets worse over time.

    Many people will put a schrader valve in the place of the pressure gauge or Tee it in beside the gauge if there is one on the AVC. Then they just add air periodically.

    I have a composite WellMate precipitation tank for my iron filter so the tank gets its air from a miconizer. If/when I have to drain the tank, I will top up the air with my compressor rather than have the micronizer slowly add the needed air.

  9. #9
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by LLigetfa View Post
    Many people will put a schrader valve in the place of the pressure gauge or Tee it in beside the gauge if there is one on the AVC. Then they just add air periodically.

    I thought of that, But By draining the tank, I can flush it out also.

    The tank seems to fill about of the way with water and that leaves % air in the top of tank.

    About the same as the AVC provided IF and WHEN it worked.
    Theory only works perfect in a vacuum.

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  10. #10
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by DonL View Post
    The tank seems to fill about of the way with water and that leaves % air in the top of tank.
    I thought you were an engineer. Simple math then says you must be running awefully low pressure if the volume of air only compresses to 1/4 of its original volume.

    http://www.engineeringtoolbox.com/co...ume-d_843.html

    The ideal volume of air would have the tank nearly empty of water at the kick-in pressure. I have personally never witnessed an AVC regulate the volume to just 25%. Most float type AVCs are about midway up the side of the tank. Whatever engineer designed your tank should not be allowed to wear his pinky ring.

  11. #11
    Jack of all trades DonL's Avatar
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    I am not even taking theory as a consideration, as to if that is the correct amount of air.

    It may be 1/3 of the water Volume, I am looking at the Condensation level on the tank for a guesstimate.

    Seems to me if you are only using half the Tank Volume to hold the water then, You are wasting large amounts of tank space.

    I am just Stating FACT and Experience, and was approximating.

    I am near Sea Level and that does change the equation. We can get into Math if You would like too.

    The type of AVC that the original poster has does not have a float.


    P.S.

    "The ideal volume of air would have the tank nearly empty of water at the kick-in pressure"
    My guesstimate was kick-off and not kick-in.

    "ideal" only happens in a Vacuum"...
    Last edited by DonL; 12-15-2011 at 08:02 AM.
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  12. #12
    DIY Junior Member jbfjr's Avatar
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    One more question, if I remove the AVC do I have to take any precautions so as not to lose prime on the pump?

  13. #13
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by jbfjr View Post
    One more question, if I remove the AVC do I have to take any precautions so as not to lose prime on the pump?
    If Your Tank input is above(Higher) than your pump outlet, Normally NO. As long as Your foot valve holds.

    Fill some Jugs of water, If You do loose prime you will have the water.


    P.S. Connecting the Small line from the pump that goes to the Air Volume Control
    First will help to keep the Pump Full of water.
    Last edited by DonL; 12-15-2011 at 08:32 AM.
    Theory only works perfect in a vacuum.

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  14. #14
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by DonL View Post
    Seems to me if you are only using half the Tank Volume to hold the water then, You are wasting large amounts of tank space.
    Huh? The amount of water that is in the tank at kick-in pressure is wasted space since the only way you will ever get to use it is to open the drain cock and capture it in a pail.

    The only useful water is that which is between the kick-in and kick-out pressures. Look at how a bladder tank works. It is nearly empty at kick-in. Some of the newer hydropnuematic tanks that claim to have near the same drawdown as bladder tanks do so by having more air and less water in them.

    People still want to buy those huge hydropnuematic tanks thinking they have more water in storage. Pfft! Ja, dead storage.

  15. #15
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by LLigetfa View Post
    Huh? The amount of water that is in the tank at kick-in pressure is wasted space since the only way you will ever get to use it is to open the drain cock and capture it in a pail.

    The only useful water is that which is between the kick-in and kick-out pressures. Look at how a bladder tank works. It is nearly empty at kick-in. Some of the newer hydropnuematic tanks that claim to have near the same drawdown as bladder tanks do so by having more air and less water in them.

    People still want to buy those huge hydropnuematic tanks thinking they have more water in storage. Pfft! Ja, dead storage.
    BIG Difference in a Bladder Tank.

    This type of tank does not have a Bladder, That is why a AVC is used.

    I am no expert on Water Well Systems, Only Rocket. I just believe what I see.

    Sorry that I even commented, There is no reason to get John Confused.


    Keep up the Good Work.



    Quote Originally Posted by LLigetfa View Post
    Huh? The amount of water that is in the tank at kick-in pressure is wasted space since the only way you will ever get to use it is to open the drain cock and capture it in a pail.
    When the Power goes off it is better to have a pail full of water than nothing at all...
    Water to Re-Prime the pump when power is restored is Nice to have.
    Last edited by DonL; 12-15-2011 at 09:14 AM.
    Theory only works perfect in a vacuum.

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