Home>Discussions>PLUMBING>Well pump short cycles
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goldhiller
Re: Well pump short cycles

My bad on my previous post, folks. Hence an alternative definition for the term "post haste", I guess.

Drawdown on a "passively" charged tank will be approx. 10% of total tank capacity. (*if* the total tank volume is available for pre-charging)

Drawdown on a pre-charged tank will be approx. 30% of total tank capacity. (*if* the total tank volume is available for pre-charging)

(Also assuming conventional points of tank connection to the water piping)

These can be calculated more closely using Boyle's law, but the rough percentages should be close enough for all "normal" applications.

Exact drawdown in either situation will vary some depending upon the pressure settings and spread of the pressure switch kick-in/kick-out settings, where the input and output pipes are connected to the tank, etc.

The difference between a passively charged tank and properly pre-charged tank is dramatic and well worth the time and effort with a single compartment galvy tank.......even though (on the average system) the water inside a single compartment galvy tank will eventually absorb the air...requiring recharge.

An exception is a well or well system which injects "excess" air into the tank each time the pump runs. You shouldn't try using a bladder type tank on such a well system as that air will be trapped inside the bladder and will then frequently come ejecting out of your fixtures in the house. A galvy tank is the better option here. However, even a galvy tank can/will actually become air-logged over time. While installing a common (cheapy) air-water volume control is better than nothing in these cases, it relegates the airhead "charge" to that of atmospheric pressure because it will open the tank to atmosphere when the float drops. This means less drawdown than with a higher precharge on the airhead, of course.

The better option if an excess air-injection situation exists is to install an Ametek US Gauge WJ type control as it is pressure-release adjustable. IOW, once properly adjusted in relation to the kick-in pressure of your particular pressure switch and then precharging the tank.....it will only release excess airhead from the tank when the water volume drops below the float level *AND* if the airhead pressure is too high. Nice device for only around $20 - 25. (As with any air-water volume control, it will only operate properly if its float remains operable & its orifice does not become clogged with "goop" .......such as iron algae, calcium deposits, etc.) You won't likely find one at a big-box, but rather at your local plumbing supply house or perhaps from a local well-driller.

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