No, doing so could cause an air leak at each pipe joint, packing gland and valve seal. Remember that the water is inside the bag. Unlike the old, plain-steel type tanks, the CA tank doesn't need to be drained.

Isolate the tank from the system and break the connection to it so that any fluid inside can be allowed to escape. The true air charge can't be determined until all the fluid is removed. The air charge will equal the system pressure until the fluid is removed from the bag. If the air charge is higher than the system pressure, there should be no water in the bag and the pressure reading should be the true air pressure reading.
    Remember, the water is inside the bag and the air is between the inside of the steel shell and the outside of the bag. If the tank does not have an air charge, air should be introduced which will squeeze any remaining water out of the bag. When the fluid stops coming out of the system connection, you will read the true air charge.

The air charge pressure should be equal to either the system fill pressure or the PRV setting if the tank is at the same elevation as the PRV. If the tank is located at any other elevation in the system, the charge pressure in the tank should be the cold pressure of the system at that elevation.

A chilled water system is filled with water at a temperature between 50 and 60ºF. When the chiller is turned on, the temperature of the water drops to 45ºF. When the water contracts, the system pressure drops, and the fill valve allows more water to enter the system to maintain the system pressure.
    If the chiller shuts down and the water in the system warms up to room temperature, the rise in temperature from 45º to ambient will cause the water in the system to expand. Without an expansion tank, the relief-valve would blow. The tank can be smaller than the one used in a hot water system, because the temperature is rising from 45ºF to ambient, instead of from ambient to 200ºF.

The CA1400 tank is top connection, and the pipe plug located at the bottom is used for draining purposes only. The warning label is to prevent installation of a permanent drain with a shut-off valve. This arrangement would not guarantee an air tight seal on the air side of the tank. The air charge would be lost, causing the bladder to become waterlogged and risking a premature bladder failure.

The screen is there to protect the bag from being forced out of the connection port when installed in a high pressure system.

The charge pressure in your tank is based on the fill pressure or operating pressure of the system where the tank is located. In a chilled water system operating at 45ºF, the tank only comes into play when the system warms up to room or ambient temperature. To recharge the tank, isolate it from the system, break the connection between the tank and the system shut-off valve, and allow the water in the tank to drain.
    Once all the water is out of the bladder, you can start charging the air/nitrogen side of the tank. The tank cannot be properly charged with water in the bladder. If the tank had lost its air charge, water will expel as you add air/nitrogen to the tank. Once the water is out and the charge is increased, you can soap up the end of the water pipe from the tank to see if any air/nitrogen is leaking out. If a drain has been installed at the bottom of the tank with a valve, remove the valve and piping and install a pipe plug. If the nitrogen line is connected to the side of the tank with a valve, I would recommend soaping the valve to see if there are any air leaks. You might want to check all the fittings with a soap solution.

If you have a bladder type tank, the air charge is to equal the cold fill pressure of the system. It appears that the pressure would be 25psi. This pressure is to be added before the water is introduced to the tank. If the water has been introduced, you can reduce the system pressure below the 12psi and then add the air. If you can't reduce the system pressure low enough, start adding air and as the system pressure starts to climb, open a drain valve to relieve the excess water coming from the expansion tank. Once the system pressure stops rising, all the water will have been pushed out of the tank, allowing you to bring the air charge to its proper level. If you have an isolation valve between the system and the tank, close the valve and break the line between the valve and tank to allow the water to escape. We show a hose bib in that line so you can connect a hose and lead the water to a drain. Once the water stops flowing, there will be only air on the outside of the bladder and no water inside.

The required pressure is dictated by the cold fill system pressure. The only water that should enter the tank is the thermally expanded water of the system. The tank precharge pressure should equal the system pressure, giving you equilibrium in your system.

When using this control, you can expect a 12-15% energy savings but this may vary more or less due to variables in the whole system.