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Thread: Is my well pressure tank damaged, undersized or WAD?

  1. #1
    DIY Junior Member
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    Default Is my well pressure tank damaged, undersized or WAD?

    I did some testing on my well tank system and the results were interesting. Heres some info :

    80 ft well, submersible pump, pump control box says 220v, 1/2 hp
    Pressure tank blue Structural Fiber w/bladder, 15" diameter x 26" tall. Charged to 38 lbs.
    40/60 well pressure switch
    4 bdrm, 2.5 bath house. 2 full baths on 2nd floor

    And my testing #s :

    Pumps fills tank from 38 lb to 58 lb in 11 seconds.
    Drawdown on tank from 58->38 lbs is 1.75 gallons
    Drawdown on tank from 58->0 lbs is 11.8 gallons

    Flow : Basement sink flow (thru filters/softener, 20 ft of 3/4" pipe and 8 ft of 1/2") = 4g in 45seconds
    Flow : 2nd floor bathtub flow = 4g in 1:11

    As I fully emptied the tank, the water got progressively dirty - red iron 'sand'. I then filled to 20 lbs and flushed many times and the water was cleaner, but still dirty. Water straight from the pump is pretty clean. I guess my tank has quite a bit of iron/sediment buildup. Is it recommended to flush out these tanks periodically?

    So... is my system working properly? 1.75g drawdown is not a lot - is the tank damaged or undersized? Since my pump is shortcycling, maybe I should put in a cycle-stop valve?

    Any comments are appreciated. Thanks

    CJ

  2. #2
    Moderator valveman's Avatar
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    The size of your tank means it should have a number WM6 on the tag. This means you should be getting almost 6 gallons of drawdown. Your tank is probably no longer charged to 38 PSI with air. Because your pump starts at 38 PSI, you should only have 36 PSI of air in the tank. However, if you have 36 or 38 PSI air in the tank, the bladder should hit the bottom at that point and you should get no more water out below 36 PSI.. When letting water out with the pump off, the pressure should drop slowly from 58 to 38 as about 5 or 6 gallons comes out. Then the gauge should drop from 36 to 0 almost instantly, as the bladder bottoms out at 36.

    Either your tank is out of air, the bladder is busted, or both. You have to air it up to 36 PSI while the pump is off and the faucet is open. If air keeps coming out of the faucet and the tank won't stay charged, then the bladder is busted. The tank could also take an air charge but weigh 160 pounds if the bladder is busted and is stopping up the discharge hole. That tank should only weigh about 10 pounds when empty.

    What busted the bladder was too much cycling on and off because that is a very small tank. It is the perfect size to use with a Cycle Stop Valve but, without a CSV your pump could have been cycling a lot with the small tank.

    Sorry I missed your email earlier. Hope this answers your question.

  3. #3
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    Thanks for the reply. My tank only says Duracell II Model DP-42-2. Very (very) rough estimate given height and diameter says its 20g size. But thats neglecting the air cell (which is replaceable).

    I did remove the tank about 5 yrs ago, and checked/adjusted the 38 lbs. The pump pressure switch does seem to come on at 38 to 58, but maybe the pressure gauge is off by 2 lbs? After it shuts off, it shakes and settles to about 55 lbs - maybe thats another sign that my tank is not 'right.'

    So you're saying the air cell takes up the entire volume in the tank when it hits the lower pressure, so the tank is completely empty of water? Wow, that is so NOT the case here. It must be broken and now is making my pump work even harder - not good. I'll have to test it. Since the aircell is replaceable is it worth tracking down a replacement?

    Funny that the few professional plumper/water ppl I had in here never said it was a small tank, even though I suggested it.

    Last, what CSV would work for me, being in the basement with 'irony' water?

    Thanks again,

    CJ

  4. #4
    Moderator valveman's Avatar
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    The CSV1Z would probably be best. I am assuming you have about a 10 GPM ˝ HP. If your pump cycles, the CSV1Z would help. If you have a sprinkler zone or something that already completely maxes out the pump, then you have a small pump and can't afford any extra friction loss. In other words even though you have a 10 GPM pump, with the CSV1Z, you will only get about 8 GPM before you start losing some pressure. If you never use more than 8 GPM anyway, you will never even know any friction loss exist.

    Yes the bladder pushes ALL the water out of the tank at the precharge pressure. The bladder flexing while the pump cycles multiple times per day, is what causes failures of bladders as well as pumps and motors. Reduce the cycling, reduce the failures.

  5. #5
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    A 10 gpm pump sounds about right from the small test data I have. And right now, my pump cycles every 2 gallons! No sprinklers here - I let the grass fend for itself. I dont have anything that could take 8gpm, so you're saying I wont notice any impact from the CSV.

    Can I ask why you said CSV1Z? The CSV1 and CSV1W seem about the same. The website has lots of info but nothing really tells you which to use. And I cant get approved to ask on their forums either...

    One more thing - Diagrams I've seen (on CSV site and elsewhere) show a check valve near the well tank, but someone else said submersible pumps already have one and it bad to have another in the basement. Your take on this?

    Thanks,

    CJ

  6. #6
    Moderator valveman's Avatar
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    There has got to be something wrong with the tank if it is cycling every 2 gallons. You won't notice any loss with the CSV1Z or CSV1W if you never use more than 8 GPM anyway. You will notice and like the "constant pressure" in the shower.

    The CSV1W works similar to the CSV1Z. The 1W is just smaller so it can fit inside the well casing if needed, so the shortness makes it a little more touchy to set but, still works fine. The CSV1 could leak on the floor if you have iron in the water so, I did not recommend that one.

    We put a check valve in the drawing to show that you still need one. If you have one on the pump, which you should, that is the only check you need.

    I deleted your email before I checked, then I could not find where you tried to register. Sorry, my bad.

  7. #7
    Moderator valveman's Avatar
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    Yes but I don't see where you tried to register. An extra check valve can cause you troubles, and if the one down hole is not working properly, it will have to be replaced anyway.

  8. #8
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    OK, I tried to register again. Maybe this one will go through.

    Regarding the check valve. Just thinking about it, I guess I must have one near the pump. If the submersible pump is open to the water, then without a check valve (or with a malfunctioning one), as soon as pressure in my tank built up, it would push the water right back down the well pipe, wouldnt it? The only way to maintain pressure in the tank is to shut off the other end with a checkvalve.

    I guess I wont bother with another until I know I have a problem with whats already there...

  9. #9
    Moderator valveman's Avatar
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    The water won’t actually come back out the pump if you have a check valve above ground. It is like holding your finger over a stray of water. Stray stays full but, it is at a negative pressure. This can draw contamination into you water if you have a small leak or loose thread anywhere. It also causes the pressure to go from negative to positive the instant the pump starts, which causes a water hammer, usually heard as a loud thump. To prevent this, the check valve at the pump must work perfectly anyway, and additional check valves are not needed.

    Some areas or states have it in their code or rules, that an additional check valve must be placed before the pressure tank, to prevent the underground line from ever being exposed to a vacuum. It is this additional check vale that causes the underground line to be exposed to a vacuum and draws in contamination. Otherwise the pressure tank could make sure the underground line always stays pressurized.

    Other states, whose engineers better understand hydraulics, make it illegal to use an additional check valve.

    When two or more check valves are used in a system, the bottom check must close first and hold completely drip tight, to help prevent these problems. This is impossible to determine, and even if 2 checks seem to work OK when new, conditions could change at any time.

    When one check valve is all you have, a leak in the check will cause the pump to cycle but, the line will never be under vacuum.

  10. #10
    DIY Junior Member pahunter's Avatar
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    cnrhome: Are you still using the DP-42 pressure tank?

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