well pressure tank - 19.2 psi = 44 psi ???

The bladder in a 1988 vintage pressure tank for home well is shot. Pump itself is 325 feet down at bottom of the well. I will probably replace the tank with one suggested from local plumbing supply wholesaler but curious on a statement seen on Filtrol brand tank seen at Home Depot the other day while picking up painting supplies.
The box for the unit claimed that this 19.2 PSI tank was equivalent to a 44 PSI unit.
What black magic are they doing to make this happen or has technology in this field improved to some great point?
Steve
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On 5/27/2012 6:33 AM, Steve Stone wrote:

It relies on the stretched rubber bladder to supply the missing pressure.
Paul
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Submersible pumps the ones at bottom of the well usually use either 30-50 or 40-60 switches this tank is set up for 20-40 or 24-44 as cut in 2-4 lbs less 19.2 PSI is empty no water in tank 44 cut off and has a 60 max Its easier to get Correct pressure by letting air to about 16-18 lbs if needed as This would be a ball park setting look for one that has 100 max and adjust the air PSI empty to 2-4 lbs less then your pressure switch before turning on the pump Don't worry about the factory precharge pressure
Robert
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The precharge is set normally to 2pis below cut-in. thus if the cut- in is 40 psi, pre-charge is set to 38.
I think the OP is misreading what he saw as that makes no sense.
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IDK what they are saying when they say a 19.2 PSI tank is equivalent to a 44psi unit, unless they mean that by using a pressurized bladder they get the same performance as a 44 psi unit....the bladder keeps the pressure at a minimum level up to the point where the tank completely empties. So if you have the bladder pressure at 19.2psi, then the tank pressure will not drop below 19.2 psi until it totally empties, at which point it plummets immediately to zero.
Without the bladder, tank pressure slowly drops to zero as the tank empties, and the last dozen gallons can trickle out at 5psi or less, which is for the most part unusable.
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Wrong. Tanks will always have a minimum pressure of whatever the cut- in is. Gauge _may_ go to zero but only if the bladder blocks off the tank outlet. In normal operation the guage will read the cut-in pressure when the pump starts, e.g., set for 30-50 with precharge of 28 the guage will never read less than 30 if everything is working correctly.
That is true whether the tank is bladderless or has a bladder.
Harry K
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I think what he is talking about is if the pump is turned off. Then the tanks do behave as he describes. The pressure goes down slowly until all the water is gone, then it suddenly plummets to zero. With a tank without the bladder at the point that occurs, you'd start having air come out and that would continue as the pressure continued a steady decline to zero as all the air came out.
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wrote:

I reread it again and still don't see that he is saying that. He sounds like he means when the pump is on.
Then

True. The bladder tank would go to zero when the bladder collapses enough to block the tank outlet. Gauge would read zero but there would still be a bit of pressure in the tank.
Harry K
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wrote:

Contact the manufacturer of the tank and ask them. What you posted makes no sense at all. Either you are reading something wrong, or this is another advertising gimmick which means little of nothing. Ads are often deceiving. Kind of like saying "our cereal contains twice the amount of vitamins as brand X." What they dont tell you is that the contents of their cereal box, is twice the weight of "brand X". (and costs 3x as much). So, yea, 40oz of cereal really does contain twice the vitamins of a 20oz box......
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On 5/29/2012 9:47 AM, snipped-for-privacy@toyotamail.com wrote:

My mistake. Company name is flotec.
http://www.homedepot.com/Plumbing-Pressure-Tanks/h_d1/N-5yc1vZbudt/R-100049233/h_d2/ProductDisplay?catalogId053&langId=-1&storeId051
Description: Featuring an appliance-like finish for a long life, the Flotec 19-Gallon Pre-Charged Pressure Tank with 42-Gallon Equivalent Rating is pre-charged to 40 psi. The tank features heavy-gauge steel construction, and the metal parts of this durable tank do not touch water. Conveniently sized, this tank is ideal for lawn sprinkling and has an air/water separator that can be replaced.
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On 5/30/2012 11:31 AM, Steve Stone wrote:

...
OK, from there can get the actual tank model and look at the manufacturer's site for it--
<http://www.flotecpump.com/ResidentialProduct_fl_hw_tk_FP7110T.aspx
It's pretty lame, but the "explanation" is on the FAQ page...
<http://www.flotecpump.com/residentialpage_resource_faq_tanks.aspx
They're claiming it's an equivalent to the volume required for equal water volume capacity to a nonpressurized air-over-water tank is what the 42 gal number represents.
--
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Thanks for pointing me in the right direction.
One design item I found of interest was their claim that the bladders in their tanks are replaceable. Does that mean it's a good design or their air bladders have short life spans???
Steve
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