Can I use a Large Pressure Tank with a CSV?

[MutantMonk]

OK... I have installed my CSV1A.

I have installed a 60/80 pressure switch and a 6 gallon pressure tank pre-charged at 55psi.

The CSV1A is installed on the main line coming from the well pump, which is a 1.5hp/18gpm unit.

The well has a static head of about 45 ft.   The well has a tremendous recovery rate so the low static head is not a limiting factor.

The pressure switch is installed in one of the side ports on the CSV1A.

The pressure tank is installed downstream about 5 feet from CSV1A.

Starting pressure is 84psi.

When I turn on a bathtub, the pressure drops from the 84psi to about 62psi where the pump turns on.

The pressure slowly builds back up to about 70psi and holds there.

If I add a sink faucet the pressure holds at about 68psi and holds.

If I add an exterior hose bib to the mix the pressure immediately drops to about 3 psi.

Is this what I should expect from the system or I am doing something wrong?

Is my pressure tank too far from my pressure switch?

The instructions say to “adjust your demand to 2-3 gpm”… do I control the demand by modulating the main valve downstream from the pressure switch?

The reason I have installed the 60/80 pressure switch and the CSV1A is to try to overcome the pressure drop through the tandem Big Blue sediment filters (a five micron followed by a 1 micron at 20” x 4.5” each). The pressure drop across the filters is about 30 psi so it really plays havoc with the system pressure.

I still don’t seem to be getting the pressure and flow that I had hoped for and would appreciate any input on this matter.

[Cary Austin]

Sorry I missed this in September?  The 30 PSI loss across the filter is your biggest problem.  Even with the CSV holding a steady 68 PSI, you are only getting 38 PSI through the filter.

I am also assuming the outside faucet is a frost free type?  Those hydrants can let out 20+ GPM, which is why your pressure drops to 3 PSI as you only have an 18 GPM pump.

[Lbear]

So would there be any harm if I installed a 40-60 gallon pressure tank with a CSV?

I have the room and the cost is not a factor.

[Cary Austin]

You can use as large a pressure tank as you want with a CSV.  However, when you are using water the CSV makes it go right past the tank, straight to the faucets.  It doesn't matter if it is a 1 gallon or a million gallon size tank.  The only time the water in the tank is used is when the pump is off and you are using something small like washing a toothbrush or filling an icemaker.  When you tank a shower or use any large amount of water the CSV just keeps the pump running steady with water going right past the tank.

Pressure tanks are not a reliable way to store water for power outages.  A 40 gallon tank only holds 10 gallons to start with, if it happens to be full when the power goes off.  Murphy's Law says the pressure gauge will always be at about 41 PSI when the power goes off, so there will not be any water in the pressure tank.

A couple of 5 gallon jugs of water in the closet is the best way to make sure you have some stored for emergencies.