I've upgraded the jet pump and pressure tank for my water system.  This larger tank improves the pressure between pump cycles and reduces the amount of cycles to maybe once every 10 minutes with the water running.

This is a Drummond 1 HP 1100 GPH well pump.  Harbor Freight was having a sale on this already well-priced pump, and I was planning to upgrade to a 20 gallon pressure tank.  The pressure tank is designed for well and cistern systems where you have a pump pull x amount of water out at a time and store it in a pressurized tank.   This avoids having a pump cycle on every time you open a faucet, with a constant stream of pressure being created by the air and water chambers in the tank.

The tank is filled with air through a tire pressure stem to 2 psi below when the water pump is set to turn on.  This gives it a baseline of pressure when it is emptied of water, which is meant to be slightly below the pressure switch's cut-in (on) pressure so that the water dips just below pressure and the adjustable spring mechanism in the switch flips to have the pump refill the tank.  

I was very pleased with the experience using PEX piping and cinch-style fasteners.  The crimp tool ratchets to the necessary pressure before it lets you release, and all of these connections were water-tight, whereas I had to keep working several of the larger threaded connections to get a seal.  I would even be interested to see these pumps and tanks sold with PEX barbed fittings for direct installation.  It's that good.

The built-in pressure switch and gauge on the pump is nice, but I was not able to get the switch working with my cistern setup without it hammering on and off once at the cut-off pressure; this was both before and after installing a check-valve at the discharge.  I installed the same ordinary water pressure switch after the check-valve, with a 40/60 psi pressure range, and it worked perfectly.  I will continue adjusting the pressure range to get it right.  This does mean using all of the water in the tank, adding air to it (to 2 psi below the new desired cut-in) and then adjusting the pressure switch accordingly.  Additionally, you can see a 75 psi relief valve installed in-line with the tank, which would open at a hard cut-off, should the pump fail-on somehow.

You can see that it's relatively simple to set up a pump and pressure tank with a fixed water supply.  You can even find these pumps with the pressure tanks built-in.  They're super compact, which is great for RV and food truck setups.  This is going into a Rinnai tankless water heater, which is also compact, hanging right against the wall.

Too many reducing connectors required for all of these threaded connections, but you can set water up 100% with fittings and components found at big-box hardware stores.

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