How to Replace a Pressure Tank For a Well

You can save a lot of money on labor and materials if you don't hire a well contractor to do everything for you in servicing your well. Of course, there are times when the do-it-yourselfer will be best served by hiring a pro, but there are many well maintenance tasks that can be done by a homeowner. Replacing your well pressure tank is one of them.

What is a well pressure tank?

A well pressure tank is a tank that serves to buffer your water pressure from your well pump so the water pressure in the house so it stays in a specific PSI range without having to cycle the pump on and off constantly. A pressure tank is designed to extend pump life, and is simply a welded steel canister with an expandable bladder inserted to maintain water pressure. It is connected to the well so that the pump pushes water into the canister (pressurized to about 2 PSI lower than your pump's low trigger setting, typically). Now the pump can turn off, and there is still water pressure in the house, because the tank is pressurizing it.

When should you replace the pressure tank?

It is easy to determine when to replace your pressure tank, because your well pump will be running more often than usual (assuming you have a CSV system where the pump is either on at full speed or off completey–we'll get into variable speed pumps later). You'll hear a clicking sound when the well pump turns on, filling the canister to capacity, then again when it turns off. When the bladder inside the pressure tank starts leaking, the well pump will have to cycle on frequently (usually every few seconds). That means it's time to replace the pressure tank or you could put excessive wear and tear on your well pump. Since that's submerged anywhere from 20 to several hundred feet, you want to avoid that if at all possible.

Sizing your pressure tank

If you are happy with your well's performance, you should probably replace the pressure tank with one of the same size. There are some circumstances where you might want to increase the size of your pressure tank or even reduce it. Depending on how much space you have available in your pump room, a larger drawdown may be more desirable for you to increase the life of your pump. This means increasing the size of your pressure tank so that more water can be used in the house before the pump needs to cycle on and refill the pressure tank.

Tanks are available from 5 gallons on up to 80 gallons or more. For systems that serve a lot of landscaping, you may even have two or three large pressure tanks.

Continuous pressure systems

The one case where you might consider reducing the size of your replacement pressure tank is if you are upgrading your pump control unit to a continuous pressure system. This type of controller, sometimes called a monodrive, rather than cycling on or off to charge a pressure tank, controls the speed of the pump to maintain constant pressure no matter what the demand is. You can have sprinklers and showers running at the same time, and the pump will adjust flow rate to meet the pressure demand (within its designed specifications, of course).

With a continue pressure controller, you don't need large pressure tanks. The pressure tank is almost obsolete in this case, but it is still recommended to have one installed, even if it's just a 5 to 7 gallon unit. This just acts as a momentary buffer, or shock absorber, for when water usage suddenly starts or stops.

The steps involved in replacing your pressure tank are easy, but some precautions must be taken to ensure your safety and avoid flooding in your pump room.

Before you start

1. Turn off your pump at the breaker.
2. Turn off gate valves to keep water from flowing via gravity back into your pump room when you remove the fittings.
3. Have a wet or dry shop vacuum handy in case of spills.
4. Have at least two large pipe wrenches and an adjustable wrench handy, along with a screwdriver.

Replacing the tank

1. Bleed pressure out of the line at the pressure relief valve using a screwdriver.
2. Unscrew the old pressure tank. If it is a large tank with 1 1/4" steel pipes, you'll need to use the large pipe wrenches. If it is a smaller unit with a hex fitting on the tank, use your adjustable wrench. Don't use the tank itself as leverage to unscrew the fittings; you run the risk of twisting off the threaded pipe that is welded to the tank.
3. If you are upsizing your tank, add more pipe sections as needed so that the new tank will be located in the correct area of your tank room. This may require purchasing some extra lengths of pipe. Do not use black pipe; it is not rated for drinking water. Always assemble pipe joints using teflon pipe thread tape or pipe joint compound.
4. Screw the new pressure tank on the assembly. Remember to tighten using the hex area of the tank with an adjustable wrench. Do not try to use the tank to tighten the joint, you can damage your tank permanently at the weld.
5. Re-tighten the pressure relief valve and turn on the other valves.
6. Turn the pump breaker back on. Since these are usually in different parts of the house, it's a good idea to have someone else watch the fittings for any major leaks as the breaker is turned back on. If there are leaks, turn the breaker back off and fix before proceeding.
7. If you turn on the system and there are no leaks, you should have a nicely working pump and pressure tank again!