Water Pressure Tank question

[Shimon]

I had a new submersible well pump and 80 gal vertical pressure tank put in a couple of months ago. I was in the pumphouse this weekend and noticed that the condensation on the pressure tank was only about 10" from the bottom (the tank is about 5' tall). I was able to wobble the tank back and forth easily as if it was mostly empty. Assuming the condensation line showed how much water was in the tank and judging by how easy it was to wobble the tank I came to the conclusion that the tank was just about mostly empty. I called the company who installed it and they said as long as the pressure gauge is reading ok (it has been showing around 50 psi) then it's ok.

I thought with the tank being 80 gal that it would hold more water. I know there is a bladder in there which creates the pressure but I would expect it to hold more water. How much water should be in an 80 gal press tank? Assuming it holds 40 gals of water...that's about 275 lbs and it sure didn't feel like there was 275 lbs in that tank.

Am I off base here? Thanks.

 

[Willl]

Sorry, but I'm afraid you are.

They will run close to empty, maybe 10-15 gals before the pump kicks in and refills.

 

[GaryQWA]

Perfectly normal with a captive air precharged type pressure tank. The "bladder" is between the water and compressed air above it, the compressed air provides the power to move water when the pump is off, and takes up 90% of the space in the tank. You work with drawn down gallons out of the tank, not the 'rating' gallons of the tank; which is very misleading but... the draw down gallons are dictated by the pressure switch setting the pump is operated at. The higher the pressures, the less gallons.

Gary
Quality Water Associates

 

[gotrocks]

I'm no expert but my pressure tank instructions say something like this.
To recharge (charge) the tank let water run out. There is a valve stem on top of the tank. It should be charged with air pressure up to ??(30?) PSI. Don't recall at the moment...too rushed to go look.
Then turn the pump back on and see what happpens. Hope this is clearer than mud.

 

[Shimon]

Thanks for setting me straight.

 

[Highbeam]

Wait until the pump kicks on and refills the blue tank and try and rock it again. You will find it is then "full" or more full. Your condensation check must have been at the low end of the cycle not long before the pump kicked on. The blue tank fills and empties between pump cycles but the tank will never fill very full.

 

[KYErik]

The air pressure in the tank must be set according to the kick on pressure of your well pump. If your well pump kicks on at 50 psi, then about 50 psi in the tank is fine. My pump kicks on at 35 psi and off at 50 psi. So I filled the empty tank with 35 psi of air. If there is always more air pressure in the tank than there is water pressure below the bladder, then that big tank isn't doing any good because it will never fill up with water.

 

[turnkey4099]

You should have the tank documents and somewhere in there it should have a chart showing the drawdown (# gallons that can be used from 'cut-off' to 'cut-on' pressure) at various pressure switch settings. The tank will never fill with water, there will always be an air bubble of some size at the top.

Normal settings are:
20-40 - not common and poor impulse sprinkler operation.
30-50 - common. That is my setting and I have had some sprinkler problems at the low end of the range.
40-60 - very good for irrigation, needle showers etc.

Pressures over 60 psi are not recommended for residential use - they cause excess wear on plumbing fixtures.

To set proper air pressure

Turn pump off, empty tank fully, add air to 2 psi below the cut-in pressure.

That optimizes pump run-time for any given switch settings, i.e., the pump will have the fewest starts. Starting is the major cause of wear on pump motors.

Harry K