Signs of Air Loss from a Home Water Tank
How do I know if my water tank has lost its air charge?

  • WATER TANK AIR LOSS SIGNS - CONTENTS: Signs that a water tank has lost its air charge - guide to diagnosing & correcting a waterlogged water pressure tank. A waterlogged water pressure tank causes short cycling "on-off" of the building water pump
  • POST a QUESTION or READ FAQs on how to determine that a water pressure tank has become water-logged or has lost its air charge

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This article describes how to diagnose the loss of and need for air in a water tank, how to add air to a building water pressure tank, and how to detect and correct air and water leaks in a building water supply system where a private well is the water source.

We also discuss how to adjust the building water pressure by setting the cut-in and cut-out pressure on the pump pressure control switch.

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SIGNS OF AIR LOSS - What are the signs of loss of air in the water tank

Waterlogged water pressure tank schematic (C) Carson Dunlop AssociatesSeveral alternative procedures for adding air to a water pressure tank are described below along with advice about what to do when things go wrong, such as finding air and water leaks.

Readers of this document should also
see WATER PUMP REPAIR GUIDE an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost.

The illustration at left is used with permission of Carson DunlopAssociates, Inc. in Toronto. [Click to enlarge any image]

  • Short Cycling of the Water Pump: If you hear the pump cycling on and off every few seconds, or if you see the water pressure squirting in short bursts at the water tap, the pressure tank needs air.

  • Condensate marks or line on the water tank: If on the outside of a water pressure tank the line of condensation is in upper 70% of tank (or higher than the normal condensate stains if such marks are visible on the tank) then there is not a large remaining air reserve. The water pressure tank probably needs or will soon need air.

    Technical notes: This article explains two basic cases of water pressure tank problems that can result in water pump short cycling:

    1. Too little air in the water pressure tank: Unless you live in a climate where there is never condensation on the exterior of the water tank, normally the (lower) portion of the tank that contains water will be cooler than the upper tank, causing the condensation of water onto the tank surface.

    If the condensate line is high on the water tank this means it's filling up with water and there is not enough air charge. (Air resides at the top of the pressure tank and water in the tank bottom.) (Water Tanks in Dry Climates: if you live in an arid climate like Arizona in the U.S. or San Miguel de Allende in Mexico you may not ever see condensation on the water tank regardless of other factors.)

    Conventional steel water pressure tanks that do not use an internal bladder to separate their air charge from the water in the tank will normally lose air by absorption into the water over time. The rate of air loss, if no leaks are present, depends on the amount of water used and on how well any automatic air volume control is working.

    A water pressure tank that has lost its air charge is called a waterlogged tank or water-logged pressure tank. We can add air back to the tank pretty easily (described below
    at WATER TANK AIR, HOW TO ADD) but we'll also want to know why the tank lost its air charge.

    Bladder type or "captive air" water tanks 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 bladder itself - a component that may be replaceable.

    2. Not enough water in the pressure tank: If your water pressure tank never shows any condensation, perhaps that's because no water or not enough water is entering the water pressure tank.

    This is the opposite problem from a water tank that has lost its air charge. We've found this uncommon case (of no water in the water tank) when the tank was defective, the pipe into the tank was clogged, or the tank was overcharged with too much air pressure. If there is too much air in the water pressure tank, this problem is usually self-correcting - the excess air leaves the tank through the supply piping to the building.

    But if the entry to the tank is blocked, or 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 tank is heavy with water it does not move easily. Be careful not to jiggle and break a pipe!

  • Water pressure surging at the sink or tub faucets: If you see the water pressure spurting or changing between good pressure and weak pressure every 5-20 seconds, the water pump is turning on and off to rapidly, and something's amiss in the system. Even if the total draw down cycle (from time the pump cut off until it cuts back on) is a minute, your system may be short cycling or close to it.

  • Pump relay clicking rapidly: If the actual water pump or well pump is located in the well or outside in a well pit rather than inside the building, you won't hear the pump turning on and off. However at the pressure tank is a pressure switch which senses the water pressure and turns the pump on (at low pressure, typically 20 psi or 30 psi) and off at the end of the pump cycle (at high pressure, typically 40 psi or 50 psi). If the relay is clicking on and off every few seconds the pump is short cycling and something's amiss in the system.

  • Effects of ambient air temperature on water tank and pump control operation are not normally any concern whatsoever, but in the off chance that your water tank is installed in an unusually hot or cold location, you'll want to review

    The mathematics
    to calculate exactly how much difference a given air pressure or air volume change makes inside a water tank is presented in our companion article Water Tank Pressure Calculations.

If your water supply problem is not described by the symptoms above the issue may with the building piping, fixtures, or the well's ability to deliver water over a sustained time - the well yield. In this case see the diagnostic guide starting at WATER PRESSURE LOSS DIAGNOSIS & REPAIR or select a topic from the More Reading links shown below.


Continue reading at  WATER TANK AIR, HOW TO ADD or select a topic from the More Reading links shown below. or select a topic from the More Reading links shown below.


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WATER TANK AIR LOSS SIGNS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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