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WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER CONSERVATION MEASURES
WATER CONTAMINANT LEVELS
WATER FILTERS, HOME USE
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL CHLORINATION & DISINFECTION
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
This article describes the location, use and repair of water tank air valves or schrader valves for adding air to the water pressure tank - the water tank air inlet valve. It's no coincidence that on many water pressure tanks you'll see what looks just like a tire valve (the black capped device at the red arrow in our photo just above).
This air valve provides an easy way to adjust the air charge in water pressure tanks.
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Captive air water tanks that use an internal bladder to keep water and air separate, such as the Well-X-Trol™ water pressure tank, will display an air valve, usually on top of the water tank, and often red in color such as shown in this photograph.
Older steel water tanks and even some modern bladder type tanks also may include an air input valve or "schrader valve" to permit air to be pumped into the tank, but it may be located in various locations.
In these installations the air valve may be located anywhere on or near the water tank such that air pumped into the valve will flow into the water tank itself.
You should not normally need to use the air valve on a water tank with an internal bladder, other than possibly an adjustment at initial installation. Even then, usually the factory air charge is the correct one for most well pump systems.
To use the water tank air valve to put air into a water pressure tank that does not use an internal bladder, see
The air valve may be found on the tank top, the tank side, on piping near the bottom of the tank such as this black-capped Schrader valve just above the relief valve in this photo, or perhaps elsewhere.
But logically you'd expect to see such a valve (if it's present at all) in a location where air inserted into the valve (say from a tire pump or from a can of compressed air) will flow into the water tank and not just out into the building water supply piping or water pump.
See WATER TANK AIR, HOW TO ADD for step by step details of when, why, and how to add air to a water tank.
See WATER TANK AIR HOW MUCH TO ADD for notes on how much air pressure to use in a water tank.
Here is a close up view of the typical air valve or schrader valve located on the top of a bladder type captive air water tank. These tanks come from the factory with air pre-charged and you do not normally need to change the air volume or pressure in these tanks.
Notice that the warning label surrounding this air valve indicates that "WARNING! Removal of cap by persons other than authorized dealer may void warranty". This is because the manufacturer is not going to accept responsibility if you over pressurized the tanks's internal system and cause damage.
Furthermore, over pressurizing any tank of any type beyond its working pressure is very dangerous and can cause the tank to rupture or explode. That's why we require a pressure relief valve on any pressurized tank, even a water tank.
Guide to Repairing Leaky Water Tank Air Valves
Sometimes when we remove the cap from a water tank air valve, or more likely when we try pumping air into the water tank at the water tank's air valve, we're troubled by water (or air) leaking back out at us from the valve - making us sorry we touched it in the first place.
If the air valve or "tire valve" or Schrader valve on your water tank is leaking water or air there are a few wonderfully easy steps you can take. We describe how to clean an air valve to get it to stop leaking, a simple emergency way to stop a leaky air valve on a water tank, and how to replace the valve stem core if that's needed.
These details are given step-by-step at WATER TANK AIR VALVE REPAIRS
Definition: Schrader valves (American Valves) and Dill Valves are used prinicipally on vehicle tires to insert (or release) air to a specified pressure. 
Schrader or Dill valves are also used, often in modified form with an internal spring with strength matched to the application where air inlet or outlet or water or air pressure management require adjustment on water pressure tanks and similar systems.
The Schrader valve or Dill valve (two different companies) consists of an externally and internally threaded metal stem.
The external valve base and stem connect (using appropriate seals or washers) to the vehicle wheel rim, or in plumbing to a water pressure tank or water piping at an appropriate location.
The internal stem of the valve accepts a replacable part, the actual control valve that opens (when a center pin is pressed) to admit air or to release air.
In reverse, pressure inside the system pushing against the valve stem core closes the valve when its center pin is not depressed. 
Similar control valves but of different diameters are used in other countries than those comprising North America.
An explanation of what water tank air valves are, what they look like, how to find them, is at WATER TANK AIR INLET VALVE.
If your well pump is short cycling (WATER PUMP SHORT CYCLING) this little air valve and a bicycle pump may be all you need to correct the trouble.
Continue reading at WATER TANK AIR VALVE REPAIRS or select a topic from the More Reading links shown below.
SNIFTER VALVES - automatic devices that insert air into water tanks that do not include an internal-bladder
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Frequently Asked Questions (FAQs) about air inlet valves on water tanks, piping, and other applications of Schrader or Dill Valves
Questions & answers or comments about finding and using the water tank air valve to adjust the pressure tank air charge
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