How to Add Air to a Water Pressure Tank by Tire Pump or a Compressed Air Source
InspectAPedia^®  -    

• How to add air to a water tank using a tire pump or compressed air at the tank air valve
• How to locate the air valve on a water storage tank
• Well pump & water tank diagnosis & repair procedures
• Questions & answers on how to add air to a water-logged water pressure tank - how to decide which air recharge pressure to use: air volume control, adding air at an air valve, or draining the water tank.

The procedure we describe below will work to add air to either type of water tank: a bladder-type captive-air tank (photo below) or a steel bladderless water pressure tank. Our photo at left shows an air inlet valve found on the tee located at the water tank base.

This water tank air addition procedure is for water tanks that do not use an internal bladder.

While it is often necessary to correct the air charge in a bladderless water tank, bladder type water tanks do not normally lose air and do not normally need to have the air pressure in tank increased unless there is a leak in the tank itself or a defect in the water-containing bladder in the tank.

Bladder type or "captive air" water tanks (shown in the photo below) do not normally need to have makeup air added. If you are experiencing water pump short cycling problems with bladder-type water tanks and the problem is not in the pump control or water piping, the problem may be traced to a failure of the water tank's internal bladder itself.

If the water-containing rubber bladder in a "captive air" water tank is defective (it can become stuck to itself and remain collapsed), the result can be a rapid on-off short cycling of the water pump. We test water pressure tanks to see if they're empty or nearly empty of water by seeing if we can rock or move the tank. If the water tank is heavy with water it does not move easily. Be careful not to jiggle and break a pipe! Bladder type or captive-air water pressure tanks and their repairs are described just above and in more detail at WATER TANK TYPES.

On most water tanks, both captive air bladder type and bladderless steel tanks, there is a fitting that looks like a tire valve located on the top of the tank, possibly at the tank bottom, or on the water outlet piping which is usually at the bottom of the tank. In the photograph shown at left, the blue cap at the top of an internal bladder-type water tank marks the location of the air valve for this water tank.

This valve can be really almost anywhere near the water tank on a pipe through which pumped air would rise into the water tank, as it is used to add air pressure to the system. Look for a little valve stem that looks just like a tire valve. In fact it is a tire valve.

These air inlet valves are technically called "Schrader valves" in case you have to buy a new one. The stem is about 3/16" diameter, and maybe 1.5" to 2" long. It might have a valve cap on it that looks just like what's on your car. That's because in fact it is the same device as used on automobile and truck tires.

Watch out: on some water pressure tanks what looks like an ordinary, simple, basic air inlet valve might be a snifter valve instead. The snifter valve stem looks like any other air inlet valve. It is different and it probably won't let you pump air into the water tank.

Snifter valves, used only on submersible well pump systems, are a type of automatic air volume control system that attempts to add a bit of air into the water pressure tank during each well pump on-cycle. We provide details about snifter valves at AIR VOLUME CONTROLS, WATER TANK

Our photo (left, Rasmussen Well Drilling, Inc., Two Harbors MN & DJ Friedman) ) illustrates a snifter valve air inlet mounted on a bronze check valve.

How to detect that a snifter valve is installed on a well water system:

If the air inlet valve you find is mounted on a check valve (usually located on the well piping just ahead of the water pressure tank inlet port) and your well system uses a submersible pump and a bladderless water tank, you may not be successful at adding air to the water pressure tank through this valve - the check valve may prevent air from passing into the water tank.

If the snifter valve is not working (often the valve clogs with rust or debris either at the air valve or at the bleeder drain on the well piping) you'll have to add air to the water pressure tank by draining the tank or by mounting an air valve directly onto a tapping on the water tank.

Also see snifter valve explanation and definition at AIR VOLUME CONTROLS, WATER TANK

1. Stop running water in the home and turn off the well pump - turn off electrical power to the pump.

2. Find the location of the air inlet valve on your water system. You may need to close the water valve between the tank and the building.

If the air valve is mounted right on the water tank itself, then you do not have to turn off water supply shut off valves for this procedure.

If the air inlet valve is mounted on a tank tee at the water tank bottom then the process will go better if you close off the main water supply valve between the water tank outlet piping and the building it supplies.

If the air inlet valve is mounted on a check valve located on well piping itself then you probably have a combination snifter valve and check valve that means that particular air valve won't send air into the water tank, but it will admit air into the well piping itself. The next time the well pump cycles on, that air will be pushed up into the water tank. Snifter valves and check valves are discussed at AIR VOLUME CONTROLS, WATER TANK,

You do not have to drain the water tank to use this procedure.

3. You can leave the water tank at whatever point in the pump on-off cycle, and tank pressure, that happens to be present. You do not need to drain water from the tank to follow this procedure.

4. Find the air inlet valve on your water tank and remove the cap. Check the condition of the valve. It should not be leaking water.

If the water tank air inlet valve is leaky you may be able to stop the leak by briefly pressing down the center pin in the valve to flush the valve seat. Otherwise you'll need to replace the valve stem core (it's a tire valve stem easily purchased at any auto supply store). Details on fixing a leaky air valve are at WATER TANK AIR VALVE REPAIRS.

Our photo (left) shows a schrader valve located on the outlet tee at the bottom of a water tank.

5. Pump air into the water pressure tank while watching the water tank pressure gauge. We recommend starting by adding just 5-10 psi of air into the tank.

If you have a bicycle pump you can simply clip the pump business-end onto this valve and pump air into the tank without going through any other rigmarole. But be prepared for having to make quite a few pump strokes. An alternative is to use a portable air compressor such as those sold at auto supply stores for re-inflating auto tires. We have also used a portable air tank that we re-filled from a nearby gas station or from a more powerful construction-type air compressor.

Watch out: don't over pressurize the water tank. If you exceed the water tank safe operating pressure it may burst, causing serious injury or even death. If you watch the pressure gauge on the water tank and keep the pressure at or below the pressure gauge cut-out pressure (typically 40 or 50 psi) or below 70 psi if your tank was totally waterlogged at the start of the procedure and the pump had just shut off, you should be ok.

Watch out: some water pressure gauges don't work, or may be slow to respond to changes in pressure. The gauge inlet port that senses water pressure may be clogged with debris. If your water pressure gauge does not change steadily as water (or air) is entering or leaving the water tank try tapping gently on the gauge. If it still doesn't work, see WATER PRESSURE GAUGES and WATER PRESSURE GAUGE ACCURACY - or replace the gauge with a new one.

WATER TANK AIR HOW MUCH TO ADD describes in more detail how much air to add to the system.

6. Turn the well pump electrical power back on. If the pressure in the water tank is below the pump cut-in pressure, the pump will start to run immediately. If pressure in the water tank is above the cut-in pressure, nothing will happen until you run some water (and pressure) out of the water pressure tank.

7. Turn on a nearby, convenient plumbing fixture (such as a kitchen sink or laundry sink).

If at step 2 you closed the main water valve between water tank and building, open that valve before trying to run water.

Run water in the house until the well pump cycles on. Turn water back off at the fixture and let the pump continue to run until it reaches its cut-off point. At that point your water tank as well as building piping will be at the cut-off pressure.

Turn water back on at a convenient location and run it, noticing how long the water runs or how much water runs before the pump turns back on. We look for a 20-30 second draw-down time before the well pump turns back on when running a typical kitchen faucet.

7. Evaluate the results. Add more air if necessary. If the draw down cycle (time before the pump turns back on) is still too small in quantity (just a gallon or two is too small) or in time (just a few seconds is certainly too little time), then you will want to add more air to the system.

8. What if you add too much air? As long as you haven't subjected the water tank to unusually high (dangerous) pressures, if you happen to over-charge the water tank with air, excess air will normally exit the tank through the house water supply piping and fixtures when they are next run. Because other problems (a leak in well piping for example) can also result in air discharge at plumbing fixtures, we provide more details at AIR DISCHARGE at FAUCETS, FIXTURES.

Fixing a leaky water tank air inlet valve: Tips for water tanks with air inlet valves that leak

If you've messed with this valve when there was no pressure on the water tank (maybe you pressed the little pin in the top of the valve) you might get water or air leaking out of the Schrader valve when you try to re-pressurize the tank.

Details about how to repair a leaky air inlet valve on a water tank are found at WATER TANK AIR VALVE REPAIRS. For your convenience we repeat a few highlights just below.

Usually you can stop this water or air leak by simply pressing the little valve-stem pin down and releasing it a couple of times. This action may successfully remove debris that may have been on the valve seat.

The valve stem end that you press looks like a little wire sticking up in the center of the Schrader valve.

If all else fails, run over to your car and borrow one of its tire valve caps and just screw it down tightly over the leaky Schrader valve.

This will work fine to stop a water or air leak until you get around to having a plumber or handy-man put a new valve stem into the misbehaving little valve.

Replacing a Schrader valve: Actually, the internal moving parts of this valve can be replaced just as they can be on a car tire. One can buy valve stem cores (and the tool to replace them) at any auto parts store.

The special tool, sometimes simply a special valve stem cap, has a protruding tip with a slot in it, used to unscrew and remove the old valve (located down inside the valve stem itself and ending with the little pin that you see when you look into the top of the valve stem) and to screw in a new valve stem core.

The internal water tank air valve stem part (valve stem core) that is replaced can be purchased with different spring strengths for different pressure ranges, but in fact, given that the pressure range of a typical water tank is 20-70 psi (like a car tire) almost any common tire valve stem core would work fine as a replacement if your valve stem won't stop leaking.