"harry k" wrote in message
...
On Sep 17, 5:38 pm, "Dimitrios Paskoudniakis"
wrote:
"Paul Franklin" wrote in message

...





On Thu, 17 Sep 2009 19:20:23 -0400, Tony
wrote:

My bladder type water tank is rated 20 gallons.

With no water I have 26.5 lbs of air pressure in tank.

The pump cuts in at about 28lbs. and out at about 51lbs.

With the tank full I only get 6.75 gallons of water before the pump runs
again. Is this right? If not, what's wrong?

Thanks

If you check pressure tank spec sheets, they will specify the "Draw
Down" rating for the different size tanks and pressure switch
settings. Draw down is the amount of water you will get between
cut-out and cut-in pressures.

A quick check of a brand or two on the web shows 20 gal tanks are
rated for about 6 gallons of draw down when using 30-50 settings.

So what you are seeing is about right for that tank with those
settings.

Switching to a larger tank will prevent the pump from cycling as
often, but you have to balance the capacity of your well and the run
time of the pump. A larger tank means the pump runs longer (although
less often). This can cause the water level in the well to fall below
the pump (low capacity well), and in extreme cases longer run time can
cause the pump to overheat.

Many of the tank and pump web sites have guidlines for sizing the tank
properly, but you need to know some details about your pump and well.
As tanks go, 20 gallons is pretty small.

HTH,

Paul F.

Get rid of the tank and go with a Grundfos variable speed pump and control
system. It pressurizes in a small two-gallon tank while it pumps and only
operates on demand. Variable speed means constant pressure. If you set it
to 70 psi, turn on the washing machine, flush a toilet at the same time
the
shower is on, the shower pressure is unaffected. Try that with a pressure
tank. I switched last year and I'm very happy.- Hide quoted text -

- Show quoted text -

Yes, but the drawback is sthat the pump runs _every_ time water is
drawn. It is the start cycle that is hardest on pumps.

Harry K

_______________________________________

The start cycle is a gradual spinup, not a sudden max speed, so incorrect
there. As for pump runs when water is on demand, so what? Ahhhhh, 70 psi.