What a pressure tank does and whether you need one
A water pressure tank (also called a pressure vessel or hydro tank) stores water under pressure so your pump doesn't run every time you turn on a faucet. Without one, a pump cycles on and off constantly, wearing out faster and creating pressure spikes that stress your pipes and fixtures. If you have a well or a private water system, a pressure tank extends the life of your pump and smooths out the water pressure throughout your home.
You need a pressure tank if you have a well pump, a booster pump system, or a rainwater collection system. If you're on municipal water, you almost certainly don't need one—the city's main line already maintains steady pressure. If you're unsure whether your system has one, look in your basement or utility room for a large metal or composite tank, usually standing upright or lying horizontally.
Installing a pressure tank is a plumbing job that involves connecting it to your pump, your pressure switch, and your main water line. The work is within reach of a homeowner with basic plumbing skills, but it requires careful attention to pressure settings and water-tight connections. If you're not confident with soldering copper or working with pressurized systems, call a licensed plumber—mistakes here can damage your pump or create leaks that are hard to find.
Key Takeaways
- A pressure tank stores water under pressure so your pump doesn't run constantly, which extends pump life and stabilizes water pressure in your home.
- Tank size depends on your pump's flow rate and how often you want the pump to cycle—larger tanks mean longer intervals between pump starts.
- The tank must be installed between your pump and your pressure switch, with a one-way check valve on the pump outlet to prevent backflow.
- Air pressure inside the tank (the "precharge") must be set lower than your pump's cut-in pressure, usually 2 pounds per square inch (PSI) below.
- After installation, you must test the system pressure and adjust the pressure switch settings to match your desired water pressure range.
Choosing the right tank size for your system
Tank size is measured in gallons and ranges from 20 gallons for small systems to 120 gallons or more for larger homes. The right size depends on two things: your pump's flow rate (how many gallons per minute it produces) and how often you want the pump to cycle.
A general rule is that the tank should hold enough water to let your pump run for at least one minute before the pressure drops enough to trigger a restart. If your pump produces 10 gallons per minute, a 20-gallon tank gives you roughly two minutes of run time—that's acceptable. If it produces 5 gallons per minute, a 20-gallon tank is too small and the pump will cycle too often. Check your pump's specifications for flow rate, then ask your plumbing supplier or the tank manufacturer which size fits your system. Oversizing is better than undersizing; a larger tank costs more upfront but reduces pump wear and gives you a buffer if demand spikes.
Tanks come in two main types: bladder tanks (with an internal rubber bladder that separates air from water) and diaphragm tanks (with a rubber diaphragm). Bladder tanks are more common in residential systems and are easier to maintain because you can replace the bladder without draining the whole tank. Diaphragm tanks are cheaper but less efficient over time. For a new installation, bladder tanks are the better choice.
Locating the tank and gathering materials
Install the pressure tank as close as possible to your pump, ideally within a few feet. The tank should be in a location that's protected from freezing (if you're in a cold climate), accessible for maintenance, and on a level surface. A basement, utility room, or pump house works well. Avoid outdoor installation unless the tank is rated for outdoor use and you can insulate it in winter.
Before you start, gather these materials: the pressure tank itself, a check valve (one-way valve) sized to match your pump outlet, a pressure gauge, a pressure relief valve, Teflon tape, pipe dope or plumber's putty, copper tubing or PEX tubing to match your existing system, soldering equipment (if using copper), and a tire pressure gauge or air compressor to set the tank's air charge. You'll also need an isolation ball valve on the pump outlet so you can shut off the system for maintenance.
Read the tank's installation manual before you begin—different manufacturers have slightly different requirements for precharge pressure and connection orientation. If the manual specifies a precharge pressure, write it down; you'll need it later.
Connecting the tank to your pump and pressure switch
The basic plumbing order is: pump outlet → check valve → isolation valve → pressure tank → pressure switch → main water line. The check valve prevents water from flowing backward into the pump when pressure drops. The isolation valve lets you shut off the system without draining the whole tank.
Start by turning off the pump and draining any existing pressure in the system. If you have an old tank, you may need to disconnect it first. Locate the pump's discharge outlet (the pipe coming out of the pump) and install the check valve there, with the flow arrow pointing away from the pump. Wrap the threads with Teflon tape and hand-tighten, then use a wrench to snug it—don't over-tighten, which can crack the valve body.
Next, connect the isolation ball valve to the outlet of the check valve. This valve lets you shut down the system for repairs without losing all your pressure. From the isolation valve, run tubing to the tank's inlet port (marked on the tank). If you're using copper tubing, solder the connections carefully; if you're using PEX, use compression fittings or crimp rings according to the tubing manufacturer's instructions. Make sure all connections are tight and dry before you pressurize the system.
From the tank's outlet port, run tubing to your pressure switch. The pressure switch monitors tank pressure and tells the pump when to start and stop. Connect it with a tee fitting so water can flow to your main line while the switch monitors pressure. Install a pressure gauge on the tank outlet so you can see the system pressure at a glance.
Setting the tank's air charge and pressure switch
Before you fill the tank with water, you must set the air pressure inside it—this is called the precharge. The precharge should be 2 PSI lower than your pump's cut-in pressure (the pressure at which the pump starts). If your pump is set to cut in at 40 PSI, the precharge should be 38 PSI.
Use a tire pressure gauge to check the air valve on top of the tank (it looks like a bicycle tire valve). If the tank is new, it usually comes precharged from the factory, but always verify. If you need to adjust it, use an air compressor to add air or a tire valve tool to release air. Write down the precharge pressure on a label and stick it on the tank for future reference.
Once the precharge is set, turn the pump on and let the tank fill. Watch the pressure gauge as the tank pressurizes. The pump should shut off when the pressure reaches your desired maximum—typically 60 PSI for a residential system. If the pump doesn't shut off at the right pressure, you'll need to adjust the pressure switch. Most switches have a large nut on top that controls the cut-off pressure and a smaller nut that controls the cut-in pressure. Turning the large nut clockwise increases cut-off pressure; counterclockwise decreases it. Make small adjustments (a quarter turn at a time) and test after each one.
The pressure range between cut-in and cut-off should be at least 10 to 20 PSI. A typical setting is cut-in at 40 PSI and cut-off at 60 PSI. Once you've dialed in the pressures, turn off the pump and let the system sit for an hour. Check the gauge again to make sure pressure holds steady; if it drops, you have a leak somewhere.
Testing the system and checking for leaks
After installation, run water at several fixtures—kitchen sink, bathroom, outdoor hose—and watch the pressure gauge. Pressure should stay relatively steady, dropping only slightly as you use water and rising again when the pump cycles on. If pressure fluctuates wildly or drops quickly, you likely have a leak or an air leak in the system.
Check all your connections visually first. Look for water dripping at the check valve, isolation valve, tank inlet, and pressure switch connection. Tighten any leaking connection by a quarter turn with a wrench. If the leak continues, turn off the pump, drain the system, and redo the connection with fresh Teflon tape.
If pressure drops steadily but you see no visible leak, the problem may be inside the tank—a failed bladder or diaphragm. This is rare in a new tank but can happen if the precharge was wrong or if the tank was damaged during shipping. If you suspect an internal leak, contact the tank manufacturer or call a plumber; the tank will need to be replaced.
Maintenance and when to call a professional
Check the tank's air pressure once a year, ideally in the fall before winter. Over time, air can dissolve into the water, lowering the precharge. If the precharge drops more than a few PSI, add air back in using an air compressor.
Inspect the pressure gauge annually and replace it if it stops reading accurately. Listen to your pump—if it cycles on and off much more frequently than it used to, the tank's bladder may have failed and the tank will need replacement. A failed bladder usually means the tank can no longer separate air from water, so the system loses its cushioning effect.
If you're not comfortable soldering copper connections, working with pressurized systems, or adjusting the pressure switch, hire a licensed plumber. Mistakes with pressure settings can damage your pump or create leaks that waste water and damage your home. A plumber can also help you choose the right tank size and precharge pressure for your specific system.
Frequently Asked Questions
What's the difference between a bladder tank and a diaphragm tank?
A bladder tank has a rubber bladder inside that separates air from water, keeping them from mixing. A diaphragm tank has a rubber diaphragm that does the same job but is less durable. Bladder tanks last longer and are easier to maintain because you can replace just the bladder. Diaphragm tanks cost less upfront but wear out faster and are usually replaced as a whole unit.
Can I install a pressure tank on a municipal water system?
You can, but you usually don't need to. Municipal water already has steady pressure from the city's main line. A pressure tank on municipal water is only useful if you want to buffer pressure spikes or if you're adding a booster pump to increase pressure in a low-pressure area. Check with your local water department before installing one, as some systems have rules about backflow prevention.
How often should I check the tank's air pressure?
Check it once a year, ideally before winter. Air can dissolve into the water over time, so the precharge may drop a few PSI per year. If it drops more than 5 PSI in a year, you may have a slow air leak in the tank valve, and the tank may need replacement.
What happens if the precharge is too high or too low?
If the precharge is too high, the tank won't fill completely with water and you'll lose storage capacity. If it's too low, the water and air will mix, the tank will become waterlogged, and the pump will cycle too often. Either way, the system won't work efficiently. The precharge should always be 2 PSI below your pump's cut-in pressure.
Do I need a plumber to install a pressure tank?
If you're comfortable soldering copper or using compression fittings, and you understand how to set air pressure and adjust a pressure switch, you can do it yourself. If any of those steps are unfamiliar, hire a plumber. Installation mistakes can damage your pump or create leaks that are hard to find and expensive to fix.