An accumulator in any hydraulic system (and that is all this is) is a vessel with a head of air pressure on it, to dampen the surges and provide pressure when the pump is not running. In aircraft hydraulic systems, they use either round steel balls with rubber diaphgrams (just like your well tank) or cylinder like units with a floating piston in it, fluid on one side, nitrogen on the other. These provide pressure for brakes and such when the pumps are off. Your 1500 gal tank is simply a storage reservoir. In most well systems, the "reservoir" is the earth itself, since you cannot draw fast enough from the ground, your system adds this extra storage capacity above ground.
The only way I can see to split it is to have two pressure pumps drawing from the 1500 gal reservoir and pumping to their own pressure tanks and houses. You cannot have one pressure pump supplying two pressure tanks that are isolated with checkvalves, as any draw on either system will require the one pump to come on to replenish the pressure. believe me, the two tanks and supply to two houses are not your problem. If the system holds 55 psi for hours on end and both pressure tank bladders are properly serviced and working, you do not have a problem. If the pressure in the house is low, your problem is elsewhere, clogged faucet aireators or screens, a clogged whole house filter you don't know exists (under the house possibly?), a glue joint in a pipe that flowed excess glue into the pipe, effective damming or restricting it, a rock or other contaminates in the line.
It does sound like you could stand to raise your pressure switch a few pounds however. Lady down the road had a drilled well put in in March. It was holding 60 psi at cut off then, the other day it was down to 53 psi, the switch had worn in and the spring settled a little, so I adjusted it slightly to get it back to 60 and the switch on pressure back up to 40 psi.
We have one community well here with the pressure switch exposed on top of a 1500 gal pressure tank in the open in direct sunlight. The max pressure varies depending on the outside temperature if cloudy or bright sun. The spring and metal in the pressure switch reacts to temperature as you would expect it to, and this causes variations in pressure. I have been tracking this with a digital pressure recorder, I record at 5 sec intervals for hours on end and graph the data to see water usage trends. Its so good I can blow up the graph and show you slight pressure variations that are people flushing commodes at 4 in the morning (I've actually show persons the graph and had them confirm that for that morning that was exactly when and what they were doing!).
Most public water systems require you to have a regulator to limit pressure to 60 psi since due to terrain and such the pressure might be much higher in the main (water tank at top of hill, you at the bottom of a valley). In England, the public systems are only required to give you 1 (one) bar of pressure at the street tap. That amounts to about 12 psi if my memory is correct, and virtually zero pressure on the second floor.
If your line to the house is long and small, you might consider installing another pressure tank at the house (basement or garage, etc) and installing a check valve to let water to the house, but keep water from the house/tank from pushing back to the well house. This will give you an accumulator of pressurized water right at the house, and possibly remedy flow issues.
Keep in mind you have to have at least one bladder or pressure tank with air head on it, directly plumbed to the pump (which is what you have right now). If you don't the pressure switch will go crazy and be switching on and off almost instantly, the pressure tanks dampen the system and prevent this (remember, water itself is not compressible, so you have to have the air "head" on the tank in some form, as the air is what you are compressing, not the water.
Have you measured the pressure at your house? Put a pressure gauge on a faucet and note the pressure, start running water elsewhere (bathtub, etc) and see what happens to the pressure. Does it fall off slowly, and never below the pressure at which the pump cuts on? or does it drop very low quickly? if it drops low and fast, then you have some sort of line restriction coming to the house.
Sorry to be so long winded, its just that I hate to see someone waste money on something that won't fix their problem.
Charles
