Well Pressure Tank Installation Instructions


A well pressure tank is an easy do-it-yourself project, almost always very easy to install. Standard tanks come with a galvanized elbow welded onto the bottom. This elbow readily accepts a PVC male adapter or short galvanized nipple.

One exception to this would be the small spin-on tanks made to install on top of the pump itself. Since they just screw on and off, instructions are self explanatory. 

A word of caution; use two pipe wrenches when tightening your male adapter or nipple into the new tank elbow, using one wrench to hold the tank elbow securely, so you don't put enough pressure on the elbow to break where it's welded to the tank when tightening up the male adapter. The weld doesn't break easily, but you want to give it a little reinforcement to be sure.

Most tanks are piped these days with PVC, so that makes the job extra easy. When cutting the pipe to remove the old tank, cut as close as possible to the tank itself in order to give yourself the maximum amount of spare pipe to use for installation of your new tank. After making the cut you can remove the old tank and plan how to pipe and couple your new tank onto the pipe you just cut.

To prepare the new tank, we usually glue a 12" inch piece of appropriate size pipe into the correct size PVC male adapter and then tighten the male adapter (four layers of teflon tape) into the tank elbow with the tank upside down or on it's side if a real large tank. This makes tightening easy. Once you complete tightening up (real tight or it will leak) the male adapter, turn the tank back over onto it's base and go to step two.

If you are dealing with galvanized pipe, tighten a replacement appropriate length galvanized nipple into the (new) tank elbow and of course you will need it to match up with the first available threaded fitting on the pump piping. Elbows and short nipples may be required, which is why I hate galvanized projects.

Step two - is the most important step - adjusting the tank air pressure BEFORE installing the tank. Standard diaphragm or bladder pressure tanks come with a factory precharge pressure of 28 lbs psi - in small and medium sized tanks, 38 lbs psi - in larger tanks. In any case - THE TANK PRESSURE MUST BE ADJUSTED TO CONFORM WITH YOUR PRESSURE SWITCH SETTING BEFORE TURNING ON YOUR PUMP.


Your tank pressure should be adjusted to conform with your pressure switch. Pressure should be set about 2-4 lbs psi LESS than the CUT-IN pressure of your pressure switch. Pressure switches generally come in three variations; 20-40 lbs psi, 30-50 lbs psi and 40-60 lbs psi. Pressure switches usually have their factory set pressure setting printed on the inside of the pressure switch cover. The CUT-IN pressure setting on a 20-40 switch is 20 lbs psi, on a 30-50 swich it's 30 lbs psi and on a 40-60 switch it's 40 lbs psi. Your "cut-in" pressure is the point at which your pressure switch will activate the pump as pressure drops due to water use. The "cut-off" pressure is the point at which the pressure switch is set to turn the pump off after water use ends.

So, 2-4 lbs LESS than your CUT-IN pressure; This means your tank bladder or diaphragm pressure setting (measured using a bicycle tire pressure gauge) on the tank air valve (usually on top of the tank) should be set at 16-18 lbs for a 20-40 pressure switch, 26-28 lbs for a 30-50 pressure switch and 36-38 lbs for a 40-60 pressure switch. You will need an inexpensive bicycle tire gauge (generally less than $2 at Walmart). Correct pressure is "set" by letting air out of the tank.

This would be a ball park setting that can be fine tuned after tank installation and testing. Of course you "set" the pressure simply by letting air out of the air valve just like letting air out of an over-inflated car tire. To fine tune later, you absolutely need to have a working pressure gauge on your pump set-up.

If the pressure setting printed inside your pressure switch cover is no longer readable, there are other ways to ball park your installation pressure. Submersible pumps usually use either 30-50 or 40-60 switches, jet type above-ground pumps usually use 30-50 switches and regular centrifugal above-ground pumps usually use 20-40 switches. You can temporarily assume and set a 27 lb (27 lbs in the tank) setting for an above ground pump, or you can use a 37 lb (37 lbs in the tank) setting for a sub pump, then be sure to properly readjust tank pressure (by letting air out) once you activate system and are able to determine the actual cut-in point of your pressure switch. Remember you must TURN OFF power to pump and drain system in order to check tank pressure.

After setting your tank bladder pressure the next step is to install the tank and turn on the pump. Determine your true bladder or diaphragm pressure setting requirement by turning on a faucet and take note of what the well pressure gauge reads when the pump actually kicks on; that is the actual CUT-IN pressure setting of your pressure switch. Your tank pressure setting (read with tire gauge) should read 2-4 lbs less than that cut-in point. 

Make sure your tank is set at 2-4 lbs LESS than your pressure switch CUT-IN point. BUT STOP! Remember you must turn off the electric to the pump and drain out all water from the tank BEFORE reading your tank bladder or diaphragm pressure.

Note - we don't recommend trying to determine pressure switch settings by running the pump before changing out the tank because most people are changing out the tank because it's waterlogged and as soon as they turn on a hose faucet the pump begins rapidly cycling on and off. Rapid cycling off and on  can damage the pump and a pressure gauge is impossible to read properly with the needle bouncing wildly back and forth.


Typical symptoms of a bad tank include hearing the pump cycle on and off repeatedly and rapidly when operating a hose or other small water use. Even with a bad tank, the pump may not cycle much with larger water uses such as an irrigation watering zone.

A test would be to allow your pump to fill the tank and automatically shut off. Then open a hose faucet and attempt to draw a bucket of water. If you hear your pump cycle on almost immediately after opening the faucet, your tank is probably bad. With most tanks larger that 30 gallon equivilent, you should be able to fill a bucket of water without having the pump kick on.

You may also notice your pump occasionally cycles on and off momentarily when no use is occurring at all if you have a drippy faucet or any other tiny leak in the water system. Theoretically, if a tank is waterlogged, even the use of one drop of water will cause the pump to cycle on and off.

Once you cut the pipe and remove the tank, you may find it is waterlogged. This occurs frequently with a bad tank. Being waterlogged means the tank has developed a small hole or tear in the rubber diaphragm or bladder. Water than very slowly flows through the small hole or tear during normal operation and fills the upper chamber (intended for air) of the tank.

As water displaces the air in the air chamber, the tank fails to perform properly and results in the symptoms described above. When you attempt to drain a tank in this condition (small hole or tear in bladder) you will find water dribbles out sometimes for hours, rather than draining immediately and quickly as a non-defective tank will.

Sometimes we run into a customer who says he cut the pipe, drained the tank for several hours, then connected back up and the tank was fine. Nope, the tank wasn't fine. The small hole in the bladder allowed his waterlogged tank to slowly drain and allowed air back into the upper (air) chamber. So when he connected back up his tank worked on a reduced basis for a few days or so, until that little old tear or hole in the bladder did its dirty work again and started kicking heck out of his pump again.

Tanks do tend to be expensive, but they are still a lot cheaper than pumps. If you allow repeated rapid cycling of your pump, you will soon need both a pump and a tank to cure the problem. Rapid repeated cycling will damage and perhaps destroy your pump.

If you have questions I haven't answered here, give us a call at 352-573-7531

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