Bladder Type Water Storage & Pressure Tanks - Diagnosis & Repair
InspectAPedia^®  -    

• How to diagnose and repair water system problems when an internal bladder water tank is installed
• What is the difference between a bladder type water tank and a glass lined no-bladder water tank?
• Broken, burst, busted or leaky water tank bladder
• Well pump & water tank diagnosis & repair procedures

Private well and pump systems include a well (the water source), piping from the well to the building, a water pump, and a water tank to which building water supply plumbing is connected.

Building plumbing fixtures (sinks, toilets, showers, tubs) are supplied with water from the building water supply piping, and drain into the building drain-waste-vent (DWV) system.

How water pressure tanks work

When water is turned on at a fixture in the building, compressed air in the water tank acts like a spring: it pushes water out of the water tank and into the building water supply piping and thus water is sent on to the building plumbing fixtures.

If many fixtures are being run at once in the building, or if the water flow rate produced by the pump and piping and controls is a modest one, the pump may run continuously all while the fixture is being operated.

More typically, if only one fixture is running and if the pump and well can deliver a high water flow rate, the pump may come on and off several times while the fixture is being run.

As water leaves the water tank, water pressure in the water tank drops. Since the water tank also contains air, the air pressure drops too. In the tank water pressure and air pressure will be at the same psi. Sketch courtesy of Carson Dunlop.

A pressure control switch, usually mounted on or near the water tank, senses the pressure drop, and at a pre-set "pump cut-in pressure" (typically 20 or 30 psi) the pressure switch turns on the water pump. See WATER PUMP PRESSURE CONTROL ADJUSTMENT for details of this control.

The water pump, located at the tank or perhaps in the well, pumps water to the building from the well, simultaneously re-pressurizing the water tank and providing water to the building. See WATER PUMP TYPES & LIFE EXPECTANCY for types of water well pumps, how they work, how they are diagnosed and repaired.

Because the water pressure tank is connected to the water pump (water in from the well) and also to the building water supply piping (water out to the building) the water tank is said to be "floated on the water line" and when the water pump is running water is pushed simultaneously into the water pressure tank and into the building supply piping.

The pressure control switch turns off the water pump when water pressure in the pressure tank reaches the "pump cut-out pressure" (typically 40 or 50 psi) - pressure switch turns off the well pump.

Bladder type or "captive air" water tanks (shown in our photo at left and in the sketch above) store the water tank's air charge in the upper portion of the steel water tank. Water in the tank moves in and out of a rubber bladder in the tank bottom. Because the air charge is kept separate from the water in the tank, air is not absorbed into the water and bladder type water tanks do not normally need to have makeup air added.

On some captive air water tanks this design is reversed. For example on the WellMate™ water tank the water is in the tank and air is in the tank bladder. This difference can confuse the burst water tank bladder diagnosis procedure which we describe below. At WATER TANK CAPTIVE AIR vs TRADITIONAL WellMate we provide separate water tank diagnosis and repair advice.

Water pressure or water pump short cycling problems with bladder-type water tanks are usually traced to a problem with the pump controls, with well and water piping leaks, or less often, to a failure of the internal tank bladder itself - a component that may be replaceable.

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 gently 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.

Bladderless Steel Water Pressure Tanks (photo at left and sketch just below) use a single steel tank interior to hold both the air charge and the water supply.

Modern steel bladderless type water tanks may be coated internally to increase the water tank life by resisting corrosion. That's what "glass lined" refers to on some water tanks. (A "glass lined" or "epoxy coated" water tank will not be a bladder type water tank which we discussed above.)

Bladderless water pressure tanks, because the air charge and water are in the same container, can lose their air charge over time (air is absorbed into the water) and may need air added. See WATER TANK AIR, HOW TO ADD for details.

Bladderless Fiberglass Water Pressure Tanks, such as the WellMate traditional hydro-pneumatic water tank operate similar to the steel water pressure tank, but incorporate a tank-top mounted air volume control and offer the advantage (over steel water tanks) of no risk of rust perforation and leak at the water tank. At WATER TANK CAPTIVE AIR vs TRADITIONAL WellMate we provide separate water tank diagnosis and repair advice for this water tank type.

Water pressure or water pump short cycling problems with bladder-type water tanks are usually traced to a problem with the pump controls, with well and water piping leaks, or less often, to a failure of the internal tank bladder itself - a component that may be replaceable.

Water tank bladder rupture: if the water containing bladder in a captive air water tank becomes ruptured, torn, or leaky, the result can be a very short water draw-down cycle before the water pump runs,or rapid on-off short cycling of the water pump. Water from the tank bladder leaks out of the bladder and into the steel tank itself where it replaces more and more of the air charge until finally the behavior of the water system is much as in the water tank bladder collapse discussed just below.

A water tank bladder might rupture from age, an internal defect, or if the pump pressure control switch is defective or is set so high that the water pressure breaks the bladder but this last cause is a bit unusual since the air pressure and water pressure on the two sides of the tank bladder's are normally the same.

Water tank bladder collapse: 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 check water pressure tanks to see if they're empty or nearly empty of water by seeing if we can gently rock or move the tank. If the tank is heavy with water it does not move easily. If the water pressure tank is empty or nearly so, it will be very light and easy to move. Be careful not to jiggle and break a pipe!

Why don't we just look at the water tank pressure gauge to see if there is water in the tank? Well we do. But because debris or other failures can cause a water tank pressure gauge to read pressure even when there is none in the tank (the gauge can get "stuck"), we don't rely on just tank gauge readings. For more about water tank pressure gauges, see  WATER PRESSURE GAUGE ACCURACY and see WATER TANK BLADDER PRESSURE ADJUSTMENT.

If the water tank is empty or nearly so, then water is not entering the tank. If the water pump runs but no water is entering the tank, the problem could be a collapsed bladder that is stuck onto itself, not admitting water. There could also be another problem such as a defective water pump, a well line leak, or other cause for water not entering the tank - so you may need to also see WATER PRESSURE LOSS DIAGNOSIS GUIDE.

If the water tank is "full" or nearly so, then if there is still no water pressure, the tank bladder could be also burst but the tank may have lost its air charge (over time air is absorbed into the water - the burst-bladder water tank is acting like a bladderless water tank discussed just above). In this case you might observe that the well pump (or pump control) is switching rapidly on and off when water is run in the building - see WATER PUMP SHORT CYCLING.

Bladder type or captive-air water pressure tanks and their repairs are described just above and in more detail at WATER TANK TYPES.

Contact Daniel Friedman for website content suggestions or for fee-paid consulting