Reduced drawdown from my pressure tank

[phils]

I have a Goulds V250 pressure tank that has a 40/60 drawdown of 4 gals. Not the 22 gals I got when it was new. Is there anything else I should check before putting in a new pressure tank?
A little history...
The system was installed 10/02 with a Goulds pump 1/2 HP #10GS05412 and a well-x-trol #302 pressure tank. The well is drilled to 50 feet with the pump set at 35 feet. The pressure tank is buried in ground with the top of the tank at ground level.
The Well-x-Trol tank failed in 03/08 (drawdown was 0) and was replaced with a Baron pressure tank #BN17002.
The Baron tank failed in 02/11 (cought this at 5 gals drawdown) and was replaced with the current Goulds V250. This one being inside the 5 year warranty was covered by the warranty.
Yes, this will be my 4th tank in 16+ years.
Both my neighbors had their wells drilled in 2002 at the same time mine was drilled. One of my neighbors well head is literally 30 feet from my well head and his pump is set at the exact same depth as my pump. Both of these neighbors are still using their original Well-X Trol #302 pressure tanks. All three were done by the same company (a highly respected driller in central Texas) and both neighbors have buried tanks like mine.

Back to my original question... Is there anything I should do/check before replacing my pressure tank yet again?
Any thoughts on why my tanks keep failing?
We have only had one incident/issue with the well, the well delivered dirty water (water with lots of sand), this occurred in 2014 (5 years ago). We flushed the well/tank/lines until the water ran clear again and have had no issues since. The drawdown at the time this happened was checked (after the water ran clear) at 20 gals +/-.

 

[Valveman]

The diaphragm or bladder in a pressure tank usually breaks from going up and down over and over as the pump cycles on and off. It is like bending a wire back and forth until it breaks. You are apparently using a lot more water than your neighbors. Or you could have a leak that is causing the pump to cycle more than your neighbors. With a 1/2HP 10GS05 all you need is a Cycle Stop Valve and a 4.5 gallon size tank.

 

[Sponsor]

 

[Reach4]

I have a Goulds V250 pressure tank that has a 40/60 drawdown of 4 gals. Not the 22 gals I got when it was new. Is there anything else I should check before putting in a new pressure tank?

Set the air precharge to 2 psi less than the cut-on pressure for your pressure switch. Precharge pressure is always set with the water pressure pretty much zero.

 

[phils]

Valveman... All three homes are second homes for retired couples. My neighbors on the left do significantly more entertaining than we do so I don't think we use more water than they do. I have checked for leaks by watching gauge pressure and have never seen a pressure drop with all outlets closed over a couple hour period. It just seems odd to me that I have had three tanks fail in such a short time. I will check for unknown water use (a leak) again. Yes, I am looking at using a CSV, but will likely also use a larger tank, with only two people in the house when the house is being used, small amount of water usage are common. On average the house is used about 2.5 days a week over a years time so very limited use. Thank you for your reply. I am sure we use a wide range of water demand over a days time. Anything from 1 to 4 faucets. We do not use the well for lawn watering. Do you have a recommendation for how to set the CSV as I understand from your posts in other threads the CSV pressure will vary with flow rate?

Reach4... I have watched the tank pressure gauge and it cycles from 40 to 60 as it should. I have not checked the schrader valve on the tank but will do so, and adjust if needed. With the tank buried, I am not sure I can empty the tank but will drain it and check. Thank you for your reply.

 

[Reach4]

Reach4... I have watched the tank pressure gauge and it cycles from 40 to 60 as it should. I have not checked the schrader valve on the tank but will do so, and adjust if needed. With the tank buried, I am not sure I can empty the tank but will drain it and check. Thank you for your reply.

If you turn off the pump, and release the water pressure at the house until the water stops, that is close enough to zero for purposes of setting and checking the air precharge.

 

[Valveman]

With only 2 people in the house and small amounts of water use a large tank is not needed, and apparently not helping so far.

A leak would also make the electric bill high. It could just be where the pressure switch is located according to the pressure tank. If the switch is too far or restricted from the tank it can cause pressure in the tank to surge before the switch shuts off the pump. This might be over-stretching the bladder. Other than that it is usually just the repeated ups and downs of the bladder from cycling that causes them to wear out.

 

[phils]

Update....
On Tues. 7/30 I drained the tank using the faucet at the well head. Power to the pump had already been turned off. A few gallons came out before I hit the 40 psi point. Most of the water came out after it went below the 40 psi point. My switch is set at 40/60. The pressure gauge in-line dropped slowly as the water left the tank. When the water quit coming out I checked the charge on the tank. The pre-charge was 0. The pressure gauge in-line also was at 0. I began charging the tank and yet more water came out, again a lot more water. There was the smallest amount of sand in the tank that came out at the very end. Light brown coloration in the last quart of water out of the tank. When the water finally quit coming out I recharged the tank to 38 psi. There was no noticeable air escaping from the open faucet after completing the 38 psi pre-charge. The drawdown returned to 20 gallons. I am measuring the drawdown with 5 gal. buckets, so 20 +/- (the tank is rated at 22 gals for a 40/60 setting).
On Thurs. 8/1 I checked the precharge and drawdown. Pre-charge is still 38 and drawdown is still 20+/-.
On Sat 8/3 I checked the precharge and drawdown. Pre-charge is still 38 and the drawdown is still 20+/-.
On both Thur. and Sat. the water runs out within a couple of gallons after the pressure hits 40 psi and the in-line gauge drops from 38 to 0 when the water is all out. The pre-charge holds at 38 psi.
I have checked the schrader valve on the tank, it is not leaking. I can only see the very top of the tank as it is buried so can't check the tank for leaks. If the tank is leaking, it is very very sloooow. I have seen 4 days with no pressure loss. I understand that is not much in pressure tank time so will keep watching it closely. There has to be a leak somewhere. Right? I have also learned I can gauge the drawdown by watching how long it takes the 10 gpm pump to recharge from 40 to 60.
Thanks to both for sharing your thoughts, it is much appreciated. The pressure switch is located within a few feet of the tank. Best guess within 6 feet of pvc pipe. When I need to replace the tank I will be moving it into a nearby shed and now know to move the pressure switch with it. I will not be burying another pressure tank.
I still can't get past the point that with my neighbors still being on their original tanks since 2002 when we all three had our wells drilled/installed by the same driller, there must be something different about my system that has been through 3 tanks, 3 high dollar tanks that should be good quality.

 

[Valveman]

Air doesn't usually get out of a bladder style tank unless there is a problem. May just take a while before you see it. When water starts getting on top of the diaphragm adding air won't help.