Pressure Tank Air Precharge Reminder, Thoughts, and Notes.

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Reach4

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I had set my air precharge about 5 years ago to 35.84 (nice gauge). I think it had dropped about 1 psi in that 5 years . I have the actual precharge I used this time recorded but not handy.

Good advice is to check air precharge once per year. My Flexcon Challenger tank has an all-butyl diaphragm, and that loses air slower than many. So until you get experience, check yours annually. Air precharge is always set while the water pressure is zero. Checking and adjusting precharge is a good time for draining sediment from your drain valve at the pressure tank too. Cycle water on and off until no more sediment comes out at the end.

Normal precharge recommendations are to set the precharge to 2 psi lower than the cut-on pressure for a submersible pump and initially 5 psi below for a jet pump. If you notice a pressure stutter, go another psi lower. It is the pressure tank's job to supply water between when the pressure switch can get the pump turned on, and the pump is pumping water. The downside of precharge being too high is you can get a momentary drop (stutter) in pressure when the pump turns on. The downside of being too low is that the diaphragm stretches more, and may have reduced life. On some tanks, there is a "top dome". That is good,because it limits the stretching, but if that comes into play, the effective capacity of the tank gets reduced.

The momentary drop in pressure will cause no other problem, unless you have a pressure switch with a low-pressure cutout (has a lever).

Those normal pressure recommendations have some margin. For example, your water pressure gauge and air pressure gauges may have a little difference in calibration. The margin can cover a small variance. Somebody with a 44 gallon pressure tank doesn't really need as much precharge as somebody who draws water at the same rate but only has a 20 gallon pressure tank. If you have a bigger pressure tank you can experiment with raising your precharge a little higher than the usual.
 
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