Accumulator Tank

I understand your dilemma about the fittings forcing you to be creative as you have.  I only wished something else could have worked for you to reduce pump vibration throughout your rig, as it did with my setup.

About 20 psi or 45 psi.....45 psi works for you and 20 psi works for me.  I might have actually set mine to 17 psi.  It would be interesting to try the water system at each setting to compare the behaviors.  I also wonder if set at 20 psi might reduce some additional vibration for me because that stores more water in my tank for more vibration cancellation.

Regarding 20 lbs, if your pump turns on at 45 like mine, I don't see how 20 lbs of pressure would work very well.  Seems like it would only use a little water out of the tank before the pressure dropped low enough for the pump to kick on again.  Just theorizing, but with the tank pressure set near the pump turn-on pressure, it should use nearly all of the 2 gallons in the tank before the pump kicks back on, which would maximize the value of having the tank. 

You nailed it. For those still wondering WHAT it all means..

The pressure the tank is at is set when the system is a '0' psi. Pressure up the system to 40 PSI, and you will find the tank pressure has increased also, up to your shutoff pressure. The water stored decreases the air volume in the accumulator, raisng the pressure on the trapped air.

My pump turns OFF at ~40 psi, (pretty sure... have yet to put a gauge on it, but thats stock setting) not 'on' as you state above. If yours turns on at 45, what is your 'off' pressure?!?

In my system, with 20 'on' and 40 psi 'off pressures, if I put the pre-pressure on the tank to 45 psi it would hold no water, as the pump would have to go above shut off to fill the accumulator.

 Likewise, should the pressure be set below turn on pressure, it will reduce the amount of water the accumulator dispenses before the pump cuts back on. It will be 'full' , sure, but not have the pressure in the bladder to deliver that water.

 Having the pressure set at slightly lower than shutoff delivers maximum volume from the tank, and minimum pump cycling.  Some may call this overthinking, others may call it understanding the operating concept to ensure peak efficiency.  Like the AC techs that charge the system to 'cold as a beer can' on the inlet side, no need to overthink it with all the wet bulb and temperature drop readings stuff...  they dont pay the electric bill on your house.    We have a name for those techs here- FORMER employees. 

Well, I'm not sure I understood all that, but whatever I did seems to work.  If I run the sink until it comes on, it runs for about another 2 minutes after I turn off the water, which I presume is the time it takes to fill a two gallon tank.  Then, if I turn the faucet back on, the water will run for about two minutes before the pump comes back on.  It would be interesting to see how much water that is, but I didn't think about measuring it when I had it all set up.  I bet it's two gallons, though.