The Pressure Tank of Mystery

Discussion in 'Pumps and Tanks Well Forum & Blog' started by LAM, Mar 3, 2010.

  1. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    I'm aware that Flotec isn't the tank of choice, but until I have the need to replace this tank it's what I have. It's an 85 gallon FP1730 and can be isolated from the well and the house plumbing with shutoff valves on either side of the tank tee. The pressure tank/switch is located in a conditioned space inside the house and the well is located 400 feet downhill (mountainside house). The well is 120 feet deep with a 3/4 hp Grundfos. The drop pipe is galvanized and the buried (5 feet) water line is 1.5" PVC. There is approximately 515 - 530 feet of total piping and probably 270 feet of head from pump to tank. The well, controller and pump are 15 years old and everything else is 6 years old. For the first 9 years of use the well was pumped with a generator for recreational use - no stopping and starting the pump, just run once or twice per week in spring/summer. With that in mind:

    Two weeks ago while doing annual maintenance I found the tank's precharge was only 10 PSI. Everything was working per usual but I brought the precharge back up to 2 PSI under cut-in, and I also rechecked cut-in/off settings. Ever since then then the tank has lost 5 PSI of water pressure overnight when it starts the night out at full capacity. For what it's worth the cut-in is 34 PSI, cutoff is 54 and precharge 32.

    For the past few nights I have allowed the tank to fill until the pump shuts off and then have closed the shutoff valves on either side of the tee ... and the tank water pressure gauge still shows a 5 PSI drop in the morning. There is no sign of a leak around the tank and everything operates normally: no air in the system, no water hammer, no short-cycling, no unusual loss of water pressure during use and during testing the tank refills and empties normally.

    The precharge is holding but yesterday I emptied the tank and pulled the schrader valve core to check for moisture. Rather than disconnect the tank from the plumbing and earthquake straps then tipping it over to check for water, I threaded a "mile" of yarn into the schrader valve and pulled it out to see if it was wet. No.

    Could the bladder still be bad? Could a worn foot or check valve in the Grunfos, even with the tank shutoff valve closed, cause some water to drain back to the well until a vacuum formed in the water pipe? Or for that matter a break in the water pipe?

    I'm stumped because I don't know how the tank can lose water pressure with the tee valves closed. I'd much rather have to replace a bad tank than pull the pump or install a new water line
  2. tuffy

    tuffy New Member

    Messages:
    8
    Location:
    British Columbia
    a leaky shut off valve and a leak in the system somewhere is most likeley. replace shut offs and test from there. that is the most economical starting point
  3. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    Thanks, Tuffy. I came to the same conclusion: a leak in the buried water line, drop pipe or pump valve ... in addition to leaky shutoff valves. I don't know what else makes sense. This morning I filled the pressure tank, closed both valves -- and 8 hours later I get the same tired result: a water pressure gauge showing a reduction of 5 pounds of water pressure in the tank. Even if the bladder is ruptured, the water should still be inside of the tank and weighing on the water pressure gauge, which is on the tee itself and isolated from the well and house lines when the valves are closed.
  4. Akpsdvan

    Akpsdvan In the Trades

    Messages:
    1,480
    Location:
    Alaska
    Is there a check valve between the pump in the well and the pressure tank?

    If there is no check valve there only the foot valve at the pump, that could be leaking or it could be a leak at the pitless or some place in the line from pump, pitless, house.

    Ground shift around the well head?

    One thing that a few people that I know have happen to them is that the ground over the pitless on the well casing has dropped down cracking the fitting at the pitless and pipe to house...

    or the guage could just not be working right any more...
  5. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    Thanks Akpsdvan. There are no check valves and I think the well goes through 30 feet of stiff clay with a 6" steel casing before entering rock. But I'll check the soil above the pitless adapter to see if it appears to have dropped.

    I don't believe the water pressure gauge is at fault but I'm willing to hope that's the problem.
  6. Akpsdvan

    Akpsdvan In the Trades

    Messages:
    1,480
    Location:
    Alaska
    When they dig to run the line, how ever deep it might be, here it is down 10', they will most of the time use gravel along with what ever they dug up so that the line could be placed..

    One thing that I have seen the well drillers do to check for pitless , foot valve leak is to in the house put a pressure gauge and a schrader valve, now they have some thing like that already put together,, then air pressure back to the pump with say 30lbs and wait......... see if there is a loss of pressure if there is, then it is check from the pitless to the pump.... if that is good then there is only one other place most likely to be the problem..

    This is not my normal field, but hang around drillers for awhile, ask questions keep the ears open.. then when one of my customers is having a challenge I can do some simple trouble shooting ,,, and then if the driller has to come in they have what I have found in trouble shooting thus saving time..
  7. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    I ran the water line... no prior experience but that's never stopped me. A neighbor crawled down the hill in his Case 580 and then we dropped in the line without rock. An air test makes a great deal of sense, pitless to tank.

    This is a very helpful website.
  8. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Pump it up to full pressure and close the valve from the tank feeding the house. Put in a top quality liquid filled pressure gauge [or tee in another one so you have 2] and try to let it sit with all the pressure on the down hill run for 48 hours, checking pressure often. If you still lose 5 pounds per 24 hours, you have a leak. Not a very serious one however. If not, run the test on the house side. Change in temperature may be giving the 5 pound variation in the isolated tank. And 5 pounds on an old gauge might be -1 or +10 pounds.

    If your flotec [blow-tek] was at ten pounds for a long time, it is very likely blown out, no matter the yarn test. Broken bladders do some very weird things hydraulically.
    Last edited: Mar 4, 2010
  9. valveman

    valveman Moderator Staff Member

    Messages:
    4,383
    Location:
    Lubbock, Texas
    I think the temperature change is your only problem. As the air and water cool down at night, the pressure will drop slightly. Just let it sit like that all day until it warms up again. See if your 5 PSI doesn't come back by itself.
  10. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    I also suspect temperature change. 5lbs is not a whole lot
  11. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    It's not temperature change. The tank is in a finished, conditioned basement room that stays exactly 65 degrees 24/7, Oct-April, and doesn't exceed 69 the rest of the year. The house is ICF construction and the temp doesn't fluctuate. The tank appears to lose about 1 PSI per hour when full and something less than that when the pressure is lower. This happens with the shutoff valves opened or closed.

    I suspect a leak down by or in the well. The difference in the house elevation and the pump is at least 270 feet - not a big deal by deep well / long water line standards but maybe enough to draw water past a closed tank valve. When I open the Merrill hydrant down by the well, and with the pump off, the water comes rushing down the water line and shoots out 100 feet at high volume... like a fire hose.

    There is a similar hydrant 100 feet downhill of the house. I think I'll fill the tank, kill power to the pump, close the tank's well-side shutoff valve and then open the hydrant. Atmosphere and gravity should allow the water in the line to at least trickle out of the hydrant. After a few hours I'll turn on the pump: if water shoots out of the hydrant within a couple seconds it should mean there is no leak in the system between the hydrant and the pump. If there is a notable lag time before water shoots out it should indicate that water had drain farther down, toward the well, meaning a leak between the hydrant and pump.

    Anyway, that's where I'll start.
  12. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    That didn't take long. Filled the tank, shut off power to the pump, closed the well-side valve opened the hydrant and allowed the water in the line to run out. It came out at about 1 gpm and didn't stop - i.e., the tank was draining even with the shutoff valve closed.

    So the 6-year-old valve is shot. And while I have described it as a tank tee valve it is actually the main shutoff for the house. The water line comes through the slab into a stud wall where the valve body is located - the outlet runs about 1 foot to the tank tee. I'll have to tear into the wall to change out the valve. But that means I still have a leak somewhere between the faulty valve and the pump.

    It might be time to call in a well guy.
  13. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    I think your test is faulty. I would leave all shut offs open, tank at 50 psi or so,shut off pump, shut off ALL water use taps. Watch pressure gauge for as long as you can.

    dont need to tear into a wall to change a valve. leave it open and install another valve in an easy spot.
  14. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    ballvalve, shutting off the individual valves is on the list for tonight, before I hit the sack. That way the system can sit for 6- 8 hours. I'd bet there isn't an internal leak but that would be preferable to a buried pipe leak. I'm not too concerned about the failed shutoff valve other than 6 years isn't long for a valve that has been turned on and off maybe 6 times. I did a little bit of the rough in plumbing and all of the finish. In fact I did much of the entire house rough in did all of the finishing, period. But I didn't install the cutoff. It's not leaking externally, so it's just not seating I guess. Maybe it was defective out of the box. Since the pump breaker is in the same room as the tank I don't really need the shutoff valve.

    You're right. As long as it doesn't impede water flow I should leave the bad valve open and install another, where the 3/4 copper comes out of the wall, before the tee.
  15. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    Closing the individual valves overnight resulted in the same 5 PSI loss - in fact now it's 7 PSI. I'll run pressure tests on the two legs of the underground line; and since the well has an in-ground shutoff at the pitless adapter, just before a hydrant, it should assist in determining if the leak is in the well components. It appears I do not have the Pressure Tank of Mystery.
  16. LAM

    LAM New Member

    Messages:
    10
    Location:
    Blewett Pass
    Mystery solved?

    It appears I have the Merrill C-1000 Frost-Free Hydrant of Mystery, rather than a tank problem. Yesterday I slapped a pressure gauge on the hydrant, located 100 feet downhill from the house, and let the system sit most of the day. Rather than the usual 5 PSI loss, the loss, measured at both the hydrant and tank, was 2 PSI. The only difference with this test being that the hydrant's handle was in the "on" position, I turned the rod/plunger adjusting nut counterclockwise (reportedly lowers the plunger in the off position), shut the hydrant, removed the gauge and let the system sit overnight at full pressure. The result was zero pressure loss this morning.

    I know little about frost-free hydrants, but when shut off it appears they can leak from the drain-down hole in the valve body, which in this case is 5 feet under grade on a steep grassy slope; such a leak wouldn't be evident on the ground. The leak might be fixed or slowed to a crawl - however, now I have a "less than satisfying" flow from the hydrant.
  17. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    They leak from the rubber seal on the end of the long rod, the water exits the drain hole [hopefully] you can pull the rod and inspect the sealing parts from the surface. Probably not a priority item if you dont use it much.
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