WellMate hydropneumatic water storage and pressure tank (C) Daniel FriedmanWellMate™ Water Storage & Pressure Tanks - Diagnosis & Repair

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Fiberglass or plastic water pressure tanks:

This article describes how to identify, diagnose and repair of WellMate™ water tanks, including both internal air bladder-type tanks (WellMate™ captive air water tanks) and bladderless traditional or hydro pneumatic type water pressure tanks such as the WellMate™ Traditional Air/Water tank: how they work, what goes wrong, how to fix it.

Here we review: how to identify the type of WellMate™ and similar types of fiberglass water tanks. How to diagnose & repair a burst air bladder in a WellMate™ water pressure tank. How to diagnose & repair lost air pressure in a non-bladder traditional WellMate hydro-pneumatic water tank.

How to diagnose and repair water system problems when an internal bladder water tank is installed and the bladder is used to contain air, not water. Broken, burst, busted or leaky water tank.

Captive air tanks that incorporate an internal, replaceable air cell or bladder, and bladderless hydro pneumatic water tanks (shown at the top of This article ), also called traditional residential water tanks that incorporate no internal bladder but use a tank top mounted air volume control.

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How to Diagnose & Repair WellMate™ type Bladder or Non-bladder Traditional Water Tanks

Reader Nancy Martin asked how to diagnose well pump short cycling and a possible water tank or bladder problem for the WellMate bladder-type water tank which uses the tank bladder to retain the air charge in a water pressure tank.

WellMate™ describes two types of water pressure tanks used in residential and light commercial applications:

Our WellMate links near the bottom of This article can direct you to photographs that help identify which type of water tank is installed at your property.

Which Type of WellMate or Fiberglass Water Tank is Installed?

These are different tank designs so first we need to know which type you have - take a look at the photos at the two WellMate links.

Captive Air Water Pressure Tanks with an Internal Air Bladder

Type 1 or captive air water pressure tanks sold by WellMate and some other manufacturers are constructed of fiberglass and use an internal bladder to hold the air charge.

If the air bladder has ruptured, the water tank will begin to act like an old-fashioned steel water tank - air absorbs into the water until there is not much air charge, the tank becomes water logged, and the well pump will short cycle on and off. Our description of conventional steel water tanks adds details. If the air bladder has failed, the tank will act much like a type 2 hydro pneumatic or traditional water tank.

Tips for Testing & Repairing a Captive Air Water Tank Bladder

Try this: if you have this type of tank, remove the valve step cap covering the bladder inflator valve located on the top of the tank. Using a small implement, MOMENTARILY (just for a second) depress the valve pin in the center of the valve stem down to see if air or water comes out. If water comes out of this valve the air bladder has burst.

But the bladder could be burst but blocking the valve in which case nothing will happen. If air comes out of this valve the the tank bladder contains air and may not have burst.

If air comes out of the valve, use an accurate tire gauge to check the air pressure at the valve.

If the air pressure is 4 psi below the well pump cut-in pressure then the air bladder is probably fine. If the air pressure is less than that figure, using a bicycle pump, just add a little air to the bladder until it is set to the proper number - 4 psi below the pump cut-in pressure.

Draining the water tank itself and adding air to a bladder type tank itself through the (ruptured) bladder valve at the tank top of a tank with a failed bladder MIGHT work to improve performance for a while (until the air is reabsorbed back into the water over time) but you need to replace the bladder.

A guide to replacing the air bladder in the WellMate captive air tank is provided by the company at

The air bladder in the WellMate™ type water tank is to be inflated to 4 psi below the well pump's "cut-in" pressure.

The installation manual for this tank is at
The tank has a 5 year warranty so check your records of when the tank was purchased to see if that applies.

Tips for Testing & Repairing a Traditional Hydro-Pneumatic (no internal bladder) Fiberglass Water Tank

Type 2 tanks, described by WellMate as hydro pneumatic water tanks, do not incorporate an internal bladder but rather an air volume control valve that replaces air into the tank as needed. These tanks will perform better than older steel water pressure tanks because we don't face the concern of rust perforation of the tank.

If the air volume control (AVC) fails, the tank will act much like a type 2 tank

See TANK TYPES: WATER, OIL, EXPANSION, ALL and scroll down to the description of older steel water tanks. In this case you may need to replace the AVC.

Draining and adding air to an AVC type tank with a failed AVC also MIGHT work to improve performance for a while (until the air is reabsorbed back into the water over time) but you need to replace the AVC.

Water tank bladder air pressure adjustment: also review WATER TANK BLADDER PRESSURE ADJUSTMENT if you are adjusting, tuning, or replacing the air pressure in your bladder-type well tank.

Reader Question: how can I tell if my water pressure tank uses an internal bladder?

How can l tell which pressure tank l have - with Bladder or without. I have CBAKX on the tank. 42 gallon upright A drain plug at the bottom an inpipe an out pipe and a pipe for pressure gauge. - Oliver 9/10/12


Oliver, see WATER TANK CAPTIVE AIR vs TRADITIONAL WellMate for a comparison of these two types of water pressure tanks.

Bladderless (no internal bladder) water pressure tanks look like this

Steel water tank (C) Daniel Friedman

Internal bladder type water pressure tanks have these properties

Bladder type Well X Trol Water Tank (C) Daniel Friedman

Contact WellMate or Pentair


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