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Water pressure strong at tank, week out of all faucets.

I have a 19 foot shallow well using a stainless well point. Atop the 1.25" well pipe is an above-ground check valve, then a fitting where a plastic line goes to a Flowtec 3/4 hp jet pump, then going to a 20 gallon stand Amtrol Well-X-Troll well tank, then to the main line that supplies the house.
Plumber just left my house after installing a new check valve from atop the well pipe. Just a NOTE: With the Check Valve off, I noticed a lot of rust along the inner walls of my metal piping...yeesh. Anyway, the plumber left with very good water pressure. I decided to open up each faucet to get the rusty water out of the system. Kitchen - done, bathtub - done, bathroom faucet...solid pressure for 5 seconds then a loss of about 80% pressure. I heard the pump turn on/off 5 times within 10 seconds (never experienced that before), and it remained on for a normal cycle. Turned the faucet back on, still low pressure. Every faucet is low pressure. Gauge on the pipe exiting the well tank reads 68 PSI, the pressure from the schrader value atop the well take is 50 PSI. I've pulled all screens from the faucets and confirmed they are clear of any debris. Do I have a blockage somewhere beyond the my pressure gauge and well tank? Thoughts

Re: Water pressure strong at tank, week out of all faucets.

A few observations:

  • The dial pressure gauge on the pipe and the measurement at the Schrader valve should read the same or within a couple of PSI (accounting for inaccuracies in the gauges) with no water flowing. Either the dial gauge or your tire gauge is faulty. Compare with another gauge; you can either get another tire gauge or a dial pressure gauge that hooks onto a hose faucet.
  • When the system is depressurized, the pressure tank (if it's a "captive" type with a water bladder) should be precharged to 2 PSI lower than the "cut in" pressure of the pump -- the pressure where the pump turns on.
  • The problem of "I heard the pump turn on/off 5 times within 10 seconds (never experienced that before), and it remained on for a normal cycle" is due to the pressure switch being too far from the tank. I'm guessing it's mounted on the water pump itself. What's happening is that when the pump first turns on, there's a surge of pressure at the switch before the pump is able to overcome the inertia of the water sitting in the pipe. This causes the pressure at the switch to quickly exceed the cutout (turn off) pressure, so the pump shuts off... but since the pressure in the system is still low, the water that just started moving has enough inertia to pull the pressure below the cut-in pressure, starting the pump again, and the cycle repeats until the water gains enough speed to even out the surges. Moving the switch closer to the tank reduces the severity of the surge so the short-cycling doesn't happen. The short-cycling can severely shorten the life of the switch, as every time it turns off or on, there is an electric arc that burns the contacts. So if it's cycling 5 times every time the pump starts, it will last only 1/5 as long as it should.
  • There is probably a restriction in the pipe between the tank and the faucets in your house. If there is any galvanized steel (or worse, black iron) pipe in the system, corrosion will build up at the fittings where there is exposed raw (ungalvanized) steel at the internal threads of the fittings. I've seen a 3/4" pipe plugged down to a hole thinner than a pencil. If at all possible, replace steel pipe and fittings with other materials such as brass, copper, or an appropriate plastic. Old "globe" valves and be restrictive; while the nominal size may be 3/4", the hole in the valve seat can be less than 1/2" diameter. I've also seen faulty gate valves where the actuator screw has broken or stripped, so the gate doesn't open completely.

If the dial gauge and the tire gauge truly were accurate, with no water flowing, there would need to be 42 feet vertical elevation difference between the dial gauge and the top of the water in the tank, because gravity is the only way to account for a difference in static water pressure!

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