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Thread: Pressure tank

  1. #61
    General Engineering Contractor ballvalve's Avatar
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    I have 4500 feet of 1.5" pvc running up a mountain to a static tank servicing a few lots. No pressure tank, on a timer.

    I get the classic shockwave pulse at pump shutoff, but I am letting a pressure relief valve for the moment blow off the wave.
    Such is a case where a spring loaded ball cone check valve every 500 feet would kill the spikes, and divide them up into much smaller and less damaging spikes. As you know, the pump Mfgr's. want a check valve every 400 feet or so. Its an old fight.

    Yes, I know - reduce the flow rate at shut off and the spike goes away, mostly - csv anyone? But in my case I cannot do that. And I dont want the burden of 5 check valves hidden in the forest either. I suppose a bag in a can is in my future.

  2. #62
    Moderator valveman's Avatar
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    Water in motion wants to stay in motion, and water at rest wants to stay at rest. Anytime you start water moving from a dead standstill or stop water moving too quickly you will have a water hammer spike. Adding multiple check valves along the pipeline “might” help with the shock wave on pump shut down, but will make the shock wave worse on pump start.

    You could use a solenoid valve with an opening and closing speed control after a pressure tank/pressure switch. Use the timer to open and close the solenoid, and let the pressure switch start and stop the pump. Opening and closing the solenoid slowly will eliminate the water hammer or shock wave.

  3. #63
    Porky Cutter,MGWC Porky's Avatar
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    How often should pump cycle? I have a 63 ft well,44 gal. pressure tank,pressure switch at 45/65,air in tank set at 43 lbs. How often should pump cycle with faucet open?
    Proper simple answer: Never!
    Porky Cutter, MGWC
    (Master Ground Water Consultant)

  4. #64
    In the Trades Plumber111's Avatar
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    Quote Originally Posted by valveman View Post
    The gauge is close to the tank, which does cushion the hammer. This is why a pressure switch must always be close to the pressure tank. Place the pressure switch too far from the tank and it will bounce on and off like a telegraph machine from the water hammer that happens when the pump starts and stops.

    If you get a cheap gauge (not liquid filled) you can see water hammer if you place the gauge at the check valve or at the faucet or maybe a dead end in the line. But it wonít show the peak of the spike and you have to look quick because water hammer only last a fraction of a second. The transient wave that happens travels down the pipes at an average 5,000 feet per second. Even if you had a thousand feet of pipe in your house, a transient pressure wave will travel the entire length of the house plumbing in 1/5th of a second. So the whole thing happens in about a 1/10th of a second. I think they make gauges that record peaks, but you can really see it in a computer generated simulation of water hammer.

    Most pumps canít even build enough pressure to pop off an insert or push loose a glued fitting. The extreme pressure from numerous little water hammer spikes each time the pump starts or stops is usually what causes damage to pipe and fittings.
    Thanks. While I believe you possibly have the test data to prove these high spikes with hammer in a traditional system, thousands of installations with millions of joints having low fail rates (when properly installed) show that they are not an issue. Yes, I have seen this fitting blow off and that fitting break etc. just as many others have seen that hammer may have contributed too. Overall though, the system is stable enough to say that the hammer and spikes in pressure are not a problem.

    Now, as a plumber that has worked on most types of pipes with varying pressures, I can say that 150 psi static pressure is a real concern and liability issue.

    For those that are using CSV's or other type pressure control valves with high pressures on the inlet side and using Black Roll PE pipe, have you had any problems or are you doing anything different for those connections?

    Thanks.

  5. #65
    General Engineering Contractor ballvalve's Avatar
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    I use 160 poly in wells and 150 psi + is common in a few of mine at the pump head. Never had a break. Use long barb fittings and 3 rated hose clamps, warm the pipe with hot water and retorque the next day, or a few hours after.

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