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Cycling Well Pump- Odd Findings

I actually got to start work on my GF's pump cycling problem. You will recall I expected to find a waterlogged pressure tank, which I had planned to replace. Here's what I found: (1) The pressure in the tank was precisely 40 lbs. With one full-open faucet: (2) The gauge exhibited normal performance- 30 lbs cut in, 60 lbs cut out- indicating normal switch operation. (3) Time 30-60: LT one minute. (4) Time 60-30: LT two minutes. This is an old Well-X-Trol Tank that appears to be about 35 gals which should be about an 80 gal standard tank equivalent. As you can see, with just one faucet running, the drawdown time seems *much* too short for a tank of this size *yet* the tank seems pressurized properly. I will admit I just started paying attention to this recently. It is possible that this has been going on for awhile and I never did see things behaving any other way. Is it possible that this has always been this way and is normal? If so, I have never seen a pressurized tank of this size behave this way. I defer to you experts... Frank

Reply to
frank1492
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I have the same size tank, maybe newer. The only odd thing I see is the settings:

Normal setting on tanks is with a 20psi differential; i.e., 40-60 or

30-50 most common.

You can only check what the pre-charge pressure is with the tank empty and pump off.

I have never measured my pump-up/drawdown times but they seem longer than a minute.

Water-logging begins with a bit of loss of the air bubble and procedes until there is only a little air left. Thus there will be _some_ air in the tank right to the end where the pump begins "hammering". Usually takes an appreciable amount of time, in my case a month or more from beginning until it becomes obvious it is short cycling.

Loss of air only has two causes, leak, sometimes at the schrader valve, or normally due to absorption into the water That is the reason for the bladder - to keep the air from being absorbed.

Harry K

Reply to
Harry K

OK, let's do the math. This is how it works if your tank was properly precharged, and is not waterlogged.

Cut-on pressure 30 psig = 45 psia, which should be the pressure in a completely empty tank. Cut-off pressure is 60 psig = 75 psia, thus at cutoff the air occupies 45/75 = 60% of the tank, so obviously 40% of the tank volume is water. 40% of 35 gallons is 14 gallons; if you draw that down in two minutes, you're getting a flow of 7 gpm.

That seems pretty unrealistic to me.

Now let's assume that you're seeing a more realistic water flow of 1.5gpm, and run the calculation the other direction, i.e. determine how much air must be in the tank to show that pressure differential at 1.5gpm for two minutes. (You can measure the actual flow rate easily enough by timing how long it takes to fill a gallon jug; then substitute that figure into this calculation.)

Obviously 1.5gpm for two minutes is a total drawdown of three gallons. If three gallons drawdown is enough to change the pressure from 75 psia to 45 psia, the air bubble has increased to 75/45 = 167% of its original size. And we know it's three gallons bigger than it was before. If 167% of the original size = 3 gallons, then the bubble at cut-off was (3 gal / 167%) = 1.8 gallons.

It _should be_ 14 gallons.

Conclusion: your tank is badly waterlogged.

Drain it completely, and pre-charge it to 28-30 psi. (The pre-charge pressure should be at, or just slightly below, the pump cut-in pressure.) Then refill with water.

Reply to
Doug Miller

My sincere thanks to Harry, and especially to Doug for his very detailed and easy to understand answer. I had forgotten that the pressure needs to be measured with the tank empty! This tank is easy to isolate and drain so I should be able to verify the actual pressure easily. As the tank is so old, I would suspect a slow leak but I will re-pressurize and watch it for awhile.

*IMPORTANT* Can I bring the pressure up with a bicycle pump? Again thank you! Frank
Reply to
frank1492

Some people can. In your case, it depends on your strength, coordination, sobriety, and stamina. And, if you have a lot of patience. And, how the system is set up. Is the expansion tank close enough to the floor, you can hook the hose on, and operate the pump?

Me, I'd rather use my 12 volt pump that travels with me in the car. Bring in the battery jumper pack to supply 12 volt power.

Or, I'd use the 3 galon pancake compressor (oilless) that I got from Harbor Freight last year.

Reply to
Stormin Mormon

Yes, you *can*, but you won't want to. Bicycle pumps are designed for bike tires which hold a small volume of air. You will be pumping for a very very long time to fill your tank.

Reply to
greenpjs

Several of us told you that in the first thread... :(

Certainly if you have the time, depending on how much volume you really need...

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Reply to
dpb

You can. But it's going to be a LOT of pumping. Do you have a friend with a portable compressor?

Reply to
Bob F

Not realistically. You are talking about a _lot_ of air. If you don't have a friend with a portable compressor, check with your local plumber for a loaner or a rental outlet.

Harry K

Reply to
Harry K

Plumbers loan tools? I hope you are kidding?

You live in Mayberry GA?

Reply to
Stormin Mormon

Sorry guess I needed to re-read.

Reply to
frank1492

Thanks all. Actually it shouldn't have made sense that it would have been any easier than doing a car tire with a bike pump!

Reply to
frank1492

Much more difficult, actually, than doing a car tire: pressure's about the same, but the volume is a *lot* higher.

Reply to
Doug Miller

I'll use my boat batttery and tire inflator.

Reply to
frank1492

Let us know how things work out!!!!

Reply to
hrhofmann

Well, it works for _me_ but then I have done one whale of a lot of business with them over the years. No, 'average Joe' isn't going to get a loan.

Harry K

Reply to
Harry K

And remember: Tank empty.

Harry K

Reply to
Harry K

How could I forget this time?........:))

Reply to
frank1492

You guys have been so generous with your time I can't thank you enough, but I have a couple more quick questions; (1) If I need a new tank, I am planning to by-pass HD and Lowes and get a Well-X-Trol (Amtrol) exactly the same as she has now. I had a Flotec pump once and was not pleased. I'd like your opinions about Flotec vs Amtrol. Do you think there is a significant quality difference? (2) Looking at the precautions on the Well-X-Trol installation sheet, am I a dead man if I try to re-inflate the old bladder? (Being facetious of course.) One would have to have a rusted shell of a tank for there to be any danger I would think, but has anyone ever heard of a plumber being impaled by metal fragments? (I feel really stupid asking because I know that's just in there for the lawyers.) ...but has anyone? Frank

Reply to
frank1492

The tank is pressurized by the well pump to however much PSI the cut off allows. So, if you pressurize to the same PSI with the hand pump, should not be any more dangerous. If the tank was going to go boom, it could explode as easily on water pressure. I'd expect it to leak at some point here or there, and then refuse to pressurize.

Reply to
Stormin Mormon

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