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How to charge a well tank....

Posted by pete_p_ny (My Page) on
Fri, Feb 16, 07 at 12:57

I have a well and a tank in my basement set at 60 and 40 psi and the cut out/in pressures. It is an OLD tank from 1963 when the house was built...no bladder. Over time, I need to recharge it. I completely drain the tank of water and usually hook up the compressor to the nipple shrader valve to assist with draining.And then I add 20 psi of air pressure with an air compressor. Than turn the well pump switch back on. Can someone confirm this is the correct procedure. I read somewhere that the air pressure added should be the same as the cut in pressure. Should I be adding 40psi of air then?


Follow-Up Postings:

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RE: How to charge a well tank....

on my tank with a bladder it says 2-3 psi less than the cut on pressure. not sure if that applies to bladderless or not.


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RE: How to charge a well tank....

With no bladder in the tank, air is slowly absorbed into the water. As this happens, the amount of drawdown from the tank is decreased. If left unchecked, the tank becomes waterlogged. When that happens, the pump cycles on and off non-stop. But you probably knew all of that anyway.

In your case, it really doesn't matter all that much as to the charge air pressure. If you just empty the tank and allow air to take the place of the water, the incoming water will compress the air inside the tank. Let's say you have an eighty-gallon tank. The water will fill up that tank until the air is compressed to 60 PSI and then the pump will shut down. So, let's say that you now have 60 gallons of water in the tank because the air is occupying the other 20 gallon space.

If you were to put 20 psi of air pressure in the empty tank, then there would be less water in the tank at the shut-off point (60 PSI) then if you hadn't charge the tank with air. The drawdown would remain the same. In other words, if you could draw 12 gallons of water before the pressure dropped to 40 psi by not pre-charging the tank with 20 PSI, then you would still get 12 gallons of water with the tank pre-charged. The only difference in my opinion, would be the amount of time it would take for the tank to become water-logged again. In my opinion, pre-charging the tank would increase that time but I cannot say by how much. A lot of that has to do with how much water is being used in the house.

As it happens, I have a bladderless 80 gallon pressure tank. I open the drain and I remove the plug at the top of the tank to let air in during the draining procedure. Once it is drained, I put the plug back into the top and turn the pump back on. I don't bother pre-charging my tank. I get a good year or so before the need arises again.


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RE: How to charge a well tank....

Last time I dealt with a tank like that, it had instructions to the effect that you drained the tank at least partially by means of a little valve that was part of the pressure gauge assembly, then I think you ran the pump with the valve open until water came out, which was 2/3 or 3/4 from the top of the tank - so your air/water ratio was set that way.

If there's no provision for compressed air and no instructions for it, I doubt you need it. You need a mixture of air and water, the water being pumped into the tank takes care of the pressure.


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RE: How to charge a well tank....

My pump has been surging for a few weeks now and just yesterday has lost much pressure and takes a long time to come on. In checking the well tank in the basement I see that it has only 1/4 or less air to 3/4+ water. I'm thinking that I need to drain/recharge it, but don't know if it is has a blader or not. Does the procedure for draining change?


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RE: How to charge a well tank....

Quick and easy way to add air to a waterlogged bladderless tank is to catch it when the pressure is almost at the cut-in pressure. Simply add air up to the cut-out pressure. Use the water normally. Doing this a few times will bring the air charge to the proper level and no water wasted. Faster and easier too.


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