How to know when a pressure tank is broken
Does the water pressure fluctuate when you're taking a show? This is a tell tale sign that the pressure tank is broken. There should be a pressure gauge installed in the plumbing somewhere near the pressure tank. With the water running, watch the gauge, does it swing back and forth between the kick in and cuttoff pressures, causing the well pump to run?
Sometimes adding air to the pressure tank will postpone the inevidiable need to replace the pressure tank. Replacing the pressure tank would be a quick job for a trained plumber, but a home owner with some simple plumbing skills should have no trouble replacing one.
Fluctuating pressure gauge
Prepare to replace the pressure tank
When getting ready to replace the pressure tank, turn off the power to the well pump. This will keep it from continueing to pump water while the work is being done. The power to the well pump will most likely need to be turned off at the breaker box.
After the well pump is turned off, drain the water out of the plumbing in the house. Turn on the lowest faucet in the house to drain the water and the highest faucet to let air into the system so it drains faster. Getting most, if not all, of the water out the plumbing in the house this way will make much less of a mess when replacing the pressure tank.
Remove the old pressure tank
The pressure tank will be connected to the household plumbing with one line, either inch or inch and a quarter. The water in the house will flow in and out of the tank as it maintains the pressure in the entire system.
Using a pipe wrench disconnection the connection to the pressure tank. Have a bucket handy, there may be some additional water at this point as it may not have all been drained from the pressure tank.
Be careful when lifting the old tank out of place as it may still be heavy from water or sediment.
Install new pressure tank
The general rule of thumb for a pressure tank size is to have one three gallons times the number of water fixtures in the house. This would include bathroom sinks, showers, washers, dishwasher etc. This number can add up quickly so a smaller pressuare tank can be used. A 20 fixture house should then look at a 60 gallon pressure tank, although this is just a suggestion.
The larger the pressure tank the more drawdown there will be before the well pump needs to kickon and it will run longer. The counter is also true, a smaller tank will require the well pump to run more often for a short amount of time. A larger tank will also have a more constant pressure as it will take longer to move from maximum pressure to the minimum.
You should be able to install the new pressure tank in the same location as the one being replaced. If it can't be installed at that location there may well be more plumbing involved. When connecting the new pressure tank back into the system be sure to use plumbers tape on all the threads to aid in making them water tight.
Once the new pressure tank is installed it is time to turn the well pump back on. This will begin to bring the water pressure in the system back up to the level set on the pressure switch. Watch for leaks as the pressure rises and tighten as needed.
Dispose of the old pressure tank properly.