A tank really does do a lot. It provides a back-up of water and pressure while insulating the pump and pressure switch from the constant rapid cycling that would occur if no tank were present. When it comes to tanks from the major manufacturers, all things and even the five year warranty and quality are pretty much the same in our opinion. We like the simplicity and color of the Flexcon H2o line of off-white tanks because the blend nicely with stucco and other modern earth colors, but that is personal preference.
Tanks are all manufactured pretty much the same in our opinion. Witness the recent "development" of changing the positioning of the bladder securing method slightly - the "bladder" immediately became a "diaphragm" instead of a "bladder" and all manufacturers jumped on the same bandwagon. That's nice, but it still looks like the same black rubber stuff to me. Same five year warranty, so it works for me.
Your pressure tank has an expandable butyl diaphragm or bladder in the bottom of the tank that collects and stores water through the inlet-exhaust fitting (elbow) on the very bottom of the tank. It works almost like a water-filled balloon inside the tank. As water enters the tank bladder or diaphragm under pressure produced by the pump, it is pressed upon by the air pressure charge that is in the entire rest of the tank airtight body. This air pressing against the diaphragm or bladder and the water therein is why you get water under pressure when you open a faucet, without having the pump cycling on and off every time you fill an eyewash cup.
When you turn on a faucet and draw water, the air pressure against the diaphragm pushes the water out of the tank and at the same time the pressure neccesarily decreases as compressed air displaces into space formerly occupied by the water filled diaphragm or bladder.
Your pressure switch monitors that situation and when the pressure falls to a point pre-determined by your pressure switch setting, your pump automatically kicks on. It runs until it forces enough water into your tank bladder to compress the surrounding air in the tank body and reaches another pressure setting (cut-off) point pre-determined by your pressure switch setting, which then shuts off the pump until another water use (or leak) causes pressure to drop to the cut-in setting point.
This all works fine until a hole or tear develops in the bladder or diaphragm. Water than matriculates gradually through the hole or tear in the diaphragm and eventually fills the chamber intended for air, which results in the tank no longer being functional because there is no air left in the tank to compress. This is called a "waterlogged" tank.
What occurs when a pressure tank is waterlogged is frequent and rapid cycling on and off of your pump each time even a small amount of water is used. Example - If you approach the pump when it is off and open a faucet to draw a bucket of water, the pump will immediately cycle on. This almost always indicates a bad tank. With a normal tank in good condition, you should be able to draw a bucket of water without having the pump cycle on.
Tanks are somewhat expensive, but are still cheaper than pumps. Rapid pump cycling will severely damage your pump if allowed to continue.
People frequently ask us what size tank to purchase. The tank rule is that bigger is better. The larger the tank, the less often your pump cuts on and off when water is used, and this is a good thing. Some general guidlines for tank sizing would be to use a 42 gallon equivilent tank for well used only for irrigation. For in-house use, a 120 gal equivilent tank is now required by many building codes and recommended as minimum size for homes with two bathrooms, but an 82 gallon equivilent tank may work out fine if only one person is occupying the home. Keep in mind the tanks sizes we've mentioned are minimum recommended size and any increase in tank size is always a better situation for the pump and the well system.
