How to Add Air to a Water Pressure Tank by Tire Pump
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

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.

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 here, the blue cap at the top of a 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 are 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.

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

Schrader Valve Tips for water tanks: If you've messed with this valve when there was no pressure on the tank (maybe you pressed the little pin in the top of the valve as described in Method 3 below) you might get water or air leaking out of the Schrader valve when you try to re-pressurize the tank.

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.

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