diaphram pressure tank

**jendend** · 03-14-2012, 05:45 PM

I just replaced my well water diaphram tank with a 20 gallon diaphram pressure tank. I set the pressure at 2 psi below the cut off pressure of the pressure switch. My question is how do you bleed off the air when filling it up with water in side the tank? Is this even necessary?

**LLigetfa** · 03-14-2012, 06:14 PM

It should be 2 PSI below the cut-on pressure, not the cut-off. What air do you need to bleed off? Do you have a bleeder/snifter that you didn't remove?

**jendend** · 03-14-2012, 06:27 PM

We did set it right--said it wrong cut on. I don't know what that this...a bleeder/snifter. It's just a regular blue standard tank. I'm thinking I don't need to bleed it but I don't understand why, doesn't air trap inside the bladder when the tank fills up?

During water usage the pump is cycling off about every two minutes, so in other words 20 pounds of pressure is lost within a two minute period during water usage when the pump has to turn on again. Is this normal, or is this too frequent? Thanks!

**LLigetfa** · 03-14-2012, 07:25 PM

Again, I'll ask, where do you think air is coming from that would need to be bled off?

How fast the tank empties is dependent on how much water you use. A 20 gallon bladder tank should have about 6 gallons of drawdown so if it empties in 2 minutes, you are drawing around 3 GPM. If you drew at 12 GPM, it would empty in 30 seconds.

How fast the tank fills back up depends on how much water the pump moves. A 10 GPM pump might not run long enough for the motor to cool down from the heat of current on the start windings. A pump should run for at least one minute and longer is better.

If you are concerned about cycling, put in a Cycle Stop Valve.

**jendend** · 03-14-2012, 07:43 PM

Thanks so much for the reply! My husband is dictating all of this to me to write, and he went to bed, but I will relay this info to him.

**Texas Wellman** · 03-14-2012, 09:26 PM

How long does the pump run once it comes on? It should be at least a minute.

**jendend** · 03-15-2012, 02:11 PM

While running the water at about 3 gal/min it takes the pump 47 seconds to cycle back off (less time - 35 sec during a normal shower). The old tank I removed was one of those 45 maybe 50 gallon galvinized tanks where you had to "charge it" prior to turing the pump on. I replaced this tank (due to leaks) with a 20 gal diaphram tank. A day day later my well pump went out (ouch!). I was not sure this was coincidence since the pump is over 15 yrs old. I replaced the old 1/2 hp 3 wire 230 Volt pump with a 2 wire 3/4 hp 230 volt pump. The pump is rated for 10 GPM & good for 175 ft well. The depth of my well is 160'.
After reading the comments about the 1 minute time span & since my Old well pump burned up, I am concerned I have an undersize diaphram tank since it takes less then 1 minute to refill when runnning the water at 3 GPM. Do you recommend a larger tank ? What is the rule of thumb for sizeing this tank? What size would you install?