I have an old galvanized holding tank with a air valve like a tire has. I had a plummer come and repressurize it about 6 months ago, he told me I would have to do it about 2x a year until I replaced it. My question is..
How much pressure do I add? ( 65psi ) I think? And do I empty the tank, and how?

The simplest way is to turn off the breaker, then drain the tank through a low level faucet. Then charge the tank with ten or fifteen pounds of air with a air compressor.

Even easier would be to replace the tank with a bladder type tank. Do you know how large the tank is?

I do plan to replace the tank, but not at this time.
Not sure how large tank is, its about 5` tall if that helps
I thought the plumber told me to add 35lbs, that's where I am mixed up

Hold the phone! Back the truck up! We're not dealing with a bladder tank. This is a pressure tank and the pump itself charges the tank by compression 6tyhe air as it pumps water into it. The air valve is there to test for a water logged tank. We had a pressure tank for years until county water came in, So why do you figure you have to add pressure? Back to you. Tom

That looks exactly like the tank with one exception, It has an air valve in the side near the top. The well guy came out about 6 months ago and added air to it, and told me I would have do do it about every 6 month or so. My question is..
How much pressure do I add? ( 65psi or 35psi ) I think? And do I empty the tank, and how?

By the way what size of a replacement tank would you recommend when I do have the money to replace it?

I'm no pump expert but I go back before bladder tanks when all we had was 40 gallon galvanized pressure tanks. I can see no advantage to adding air pressure to a pressure tank. The pump compresses the air as the tank fills, I can , however, se the disadvantage.
By adding air to a pressure tank you decrease the amount of water the tank will hold.
For instance. If you precharged the tank with 20PSI and the control box cuts off at 65PSI then your pump would shut down at 45 PSI because the control box would think you've already reached 65PSI. If I'm in error and things have changed since I was out in the field perhaps another expert will chime in and educate me. But I still can't see the sense in reducing the volume of water a pressure tank will hold. That's why we have pressure tanks. Regards, Tom

Galvanized tanks are supposed to be charged with air from the wellpipe. However, for that to happen, there is a second air valve somewhere around the wellhead which allows air to enter the wellpipe when the pump shuts down. The water in the wellpipe runs completely out and is replaced by air. When the pump cuts back on, that air is pump into the tank. To keep the tank from filling completely with air, there is a valve about halfway up which releases excess air. I'm going to guess your tank does not work that way. Might have done so at one time, but from your description, it no longer does. So, the air in your tank is gradually absorbed into the water over a period of a few months. Once it is largely gone, it must be replaced. It doesn't matter how much air you put in the tank so long as you don't go overboard. The main thing is to first drain the tank. Then I would add twenty pounds or so of air pressure. When you turn the system back on, then the water will compress the air until you get to the cut off pressure, whatever that is. It will work fine for a few months, at which point you will have to recharge the tank.

The site below has a pretty good description of this:

http://www.pumpsandtanks.com/faq_page.htm#galvanized

By precharging the tank by 20 pounds your decrease the volume of water entering the tank as it will shut the pump down sooner. Is that a good thing? You precharge a bladder tank but back in Wisconsin before moving to Florida, all our pumps had 40 gallon pressure tanks. Nobody ever had to precharge them back them. What's changed and what's the advantage of reducing the water volume in the tank? Comer on guys! I'm ready to learn. Tom

I would precharge a galv tank just to increase the time before I have to recharge it again. More air = longer interval. The amount of water entering the tank is not the issue as much as drawdown is the issue. I don't see it impacting drawdown at all. Could be wrong.

I guess I just see it as the easiest way to do a job that is not on a level of placing a man on the moon. You need air. Well, drawdown as much water as you can, then add air through the air valve. Job done. Go in and watch football.

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I would precharge a galv tank just to increase the time before I have to recharge it again.

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My point exactly, Why recharge in the first place?

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More air = longer interval.

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Using that as a guide then why not charge 75 or 100 pounds?

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The amount of water entering the tank is not the issue as much as drawdown is the issue.

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Silly me! And here I always thought pressure tanks were designed to store water.
What , exactly. Do you call a "drawdown"?
Seems to me with more air and less water in the tank you wouldn't have that much less to draw on. If you have a 20/40 control box that pump''s going to shut down when the psi reaches 40 PSI If you charge the tank with 20 pounds then the pump will shut down at 20PSI because you already have 20Pounds of air in the tank.

Now I'll go back to my oroginal question. Where I grew up all we had were shallow well pumps and 40 gallon pressure tanks. The pump itself charged the tank. We didn't find it necessary to charge a pressure tank then and our water sy7stems ran just fine.
The same set up as we have today, What's changed since then? Or are you guys so used to charging bladder tanks you thin it's better to charge up a pressure tank? Cheers, Tom

You wouldn't charge 75# for the simple reason that the switch would never cut the pump on. The same thing would be true if you charge a bladder tank to 75#.

You recharge a galv tank because it is waterlogged... out of air.

Drawdown is the amount of water a person can "draw" from a tank before the pump cuts back on. Putting more water in a tank does no good by itself unless it increases the amount of water the tank can deliver before the pump cuts back on. Following your logic, a waterlogged tank, which is FULL of water, should be the ideal situation. We know, of course, that it is not.

Other sites recommend that the owner remove the plug from the top of the tank, allow all of the water to drain out (which allows the tank to fill with air), replace the plug, and turn the power back on. I'm sure that would work, but I could miss the first quarter by the time I finish that.

If a galv tank is being charged by air from the wellpipe every time the pump kicks on, then you don't ever need to recharge the tank. Evidently that is not happening in this guy's case, as is apparent from the fact that a plumber came out, recharged the tank, and told him he would have to do that again himself in a few months. Could be a lying, money-grubbing plumber, but I doubt. I think it is what it is. A bladder tank would solve his problem.

I was in that very situation a few years ago after I had my pump and wellpipe replaced. The well guy, for whatever reason, took out the bleeder valve and told me to just add some air to the tank from time to time. I just got in the habit of every couple of months, I would cut off the power, open a spigot, and just keep adding air as needed to keep the pressure at whatever level it was as water continued to drain out. I'd drain ten or fifteen gallons, and then just cut the power back on. That way I didn't run the risk of short-cycling with a waterlogged tank. I finally just put in a bladder tank. My tank is outside in a pumphouse, so doing anything is a pain, but having to completely drain the tank and then opening a plug to allow air in would have been a mess.

Might add that it was that experience that caused me to look around and find this site. Have enjoyed it a great deal and learned a lot from you guys.

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If a galv tank is being charged by air from the well pipe every time the pump kicks on, then you don't ever need to recharge the tank.

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This is correct only if you have an AAC (Automatic Air Control) valve and its associated sniffer valve. If you have an AAC valve and the tank is becoming water logged, either replace the AAC valve (after checking the associated sniffer valve), or periodically charge the tank (empty) to two pounds less than the cut in pressure of the pump, just as you would as if it were a bladder tank.

If you do not have a tank drain valve, open the closest, lowest faucet and drain the tank. With the faucet open, add air to the tank until you get air out of the faucet. Close the faucet and pressurize the tank to # 2 lbs below the cut in pressure.

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You recharge a galv tank because it is waterlogged... out of air.

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No you don't! You shut the pump off and drain the tank, As the pump pumps up to pressure it recharges the tank,

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Drawdown is the amount of water a person can "draw" from a tank before the pump cuts back on.

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OK, and air is better then water because?

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Other sites recommend that the owner remove the plug from the top of the tank, allow all of the water to drain out (which allows the tank to fill with air), replace the plug, and turn the power back on.

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That's the way we always have don it. ONE MORE TIME! Same pump, same 40 gallon pressure tank. What's changed between then and now? Like I said, I'm ready to learn. Regards, Tom

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OK, and air is better then water because?

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Air and water are both essential. No air... no pressure. No water... no drawdown.

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That's the way we always have don it. ONE MORE TIME! Same pump, same 40 gallon pressure tank. What's changed between then and now? Like I said, I'm ready to learn. Regards, Tom

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As I said earlier, I had to do that as a homeowner for a couple of years. To me, if you do it your way, you start with zero pressure in the tank at the point when you turn the power back on. That, to me, is the problem. From day one, you start losing air in a galv tank that is not being recharged from the wellpipe. So it's just a matter of time before you have to do this again. If you put a low charge of air in the tank, you have more air and the charge will last longer. I'm quite sure the way you have described will work. I am convinced that what I have described is a better way. As I said, air is what you are going to start losing from day one. More air = a longer interval before you have to do it all again. I see positives, but no negatives.

If the tank is being recharged from the wellpipe, and as HK noted has an AAC valve about halfway up the tank to control the amount of air in the tank, then you don't have to do any of this. It's only if you are not setup in that fashion that you would have to recharge the tank.

Honestly, its not a big deal to me. If you would rather I not advise people on this site to handle it in the way I've described, I can simply advise they do it your way as I know it will work. Having gone through it myself, I also know my method will work, is much easier to do, and will provide a longer-lasting charge of air. But I'm OK with it one way or the other. I come to this site to have a little fun, learn a lot, and provide what assistance I can. It's the best plumbing site I know of and I've recommended it to several people and will continue to do so. No big deal.

Have a great Thanksgiving. We all have much to be thankful for. Amen?

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From day one, you start losing air in a galv tank that is not being recharged from the wellpipe. So it's just a matter of time before you have to do this again. If you put a low charge of air in the tank, you have more air

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Can't buy that! Just how do you figure you loos air out of a watertight tank? And every time the pump kicks on it recharges the tank. It don't need your help. It does just fine for itself.
How many times do I ask this before I get a answer? Same pump, same 40 gallon pressure tank. What's changed between then and now? I'm waiting, Tom

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Can't buy that! Just how do you figure you loos air out of a watertight tank?

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Tom,
Try this logic.
Air, especially air under pressure, is absorbed by the water. Hence, the reason that tanks become "water logged", also the reason bladder tanks were invented to keep the air and water masses separated.

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I had a plummer come and repressurize it about 6 months ago, he told me I would have to do it about 2x a year until I replaced it.

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That is the testimony of the OP. Was his plumber a scumbag liar, or was he doing what needed to be done? It just seems obvious to me that this galv tank is, for whatever reason, not being recharged with air from the wellpipe. That being the case, it will eventually waterlog. Are you seeing it differently?