Bulging and Leaking in Water Heaters

Bulging and Leaking in Water Heaters
May 24, 2012 Lorelie

Tank-type water heaters are very useful at home, and that is why it is a must that it works perfectly fine all the time.  But what if you notice that your water heater unit seems to be bulging and leaking?

What can cause a water heater to bulge?

Bulging and leaking in water heaters are typically caused by an increase in the pressure of hot water that is inside the tank.

An excessive hot water pressure in the tank can lead to a bulging water heater and it can potentially deform the tank permanently.  After this happens, problems will occur such as water heater leaks as well as the flue pipe and pipe fittings would be dislocated.

The common symptoms that you will notice on your water heater when there is an occurrence of excessive pressure are:  when the topmost part of the water heater has cockeyed nipples, and the bottommost part of the head is reversed or bulged.

Tank-type water heaters are basically designed and thoroughly tested on maximum internal water pressures of about 300 psi, without any traces of distortion.  If in case there is an appearance of deformation on your tank, such as the bulged bottom, chances are that your water heater was subjected to pressures of more than 300 psi.  Generally, the maximum working pressure for which the water heater was designed is supposed to be approximately 150 psi.

When water inside the water heater is cold, there should be only a static pressure of water on the tank, which is a result of the water weight.  From the moment that you turn the water heater ON, and the heating process begins, the temperature of the water will increase as well as the volume, and the pressure will only keep going up.

How to Prevent the Increase of Pressure in Water Heaters

If your tank-type water heating system is an open system, and if in case there are no obstructions that can reverse the flow, then the water pressure inside the tank will always be closed to the cold water supply.  The hot water will tend to expand back into the cold water supply, and there will be no damage done to the plumbing system.  In this situation, the chances for a bulging water heater are absolutely minimal.

If there are obstructions, such as in the checking valves, pressure-reducing valves, the shut-off valve, in the cold water line and there is presence of water softeners, then the system becomes a closed system.  In this situation, the heated water will cause pressure to increase quickly, until something ruptures or fails.  This is the reason why the expansion tank is a must to use, in order to accept the additional pressure.  If in case the expansion tank was not installed, then the hot water pressure may become too great which can cause bulging of the water heater unit or the tank may even rupture.

The correct size of the expansion tank must be used on each and every new water heater installation in order for it to maintain a consistent and safe working pressure.  Do keep in mind that the warranty will be voided, so it will be at your expense if something undesirable happens to your water heater unit.

Water, a non-compressible liquid, expands when heated.  For each 10°F increase in water temperature, the water expands at about 0.2%.  As the temperature increases, the maximum designed water pressure can possibly exceed and therefore cause bulging to the water heater unit.

How to Test Hot Water Pressure inside a Water Heater Unit

One of the most common reasons why your tank-type water heater is leaking may be that there is pressure buildup or there is a significant drop-off inside of the water heater tank (bulging water heater).  Below are some steps regarding a simple do-it-yourself project wherein the only tool that you will use is the pressure gauge.  When your water heater leaks, it tends to create a puddle on the floor as there is a hole or crack in the tank, or there are dislocated plumbing connections or unions.  The steps below will help you to check and how to properly test hot water pressure:

To get the pressure reading inside of the water heater tank, install a pressure gauge on the drain valve outlet and open drain valve.

  • Close the main shut-off valve that supplies the water heater.
  • Ensure that all the hot water taps are turned off.  When the water heater is running and because all the hot taps are closed, pressure will then build up inside the tank.
  • Run the water heater by means of turning the thermostat up until the main burner or the heating element comes on.  Ensure that you constantly check the pressure gauge as the pressure in the tank will tend to increase rapidly.
  • When the hot water pressure begins to rise up, shut the water heater off by turning down the thermostat.  Then, watch the pressure gauge to see if it holds the pressure or if it drops off significantly.
  • If there are no leaks occurring around the fittings when the pressure drops, that means the tank is leaking.
  • If the pressure inside the water heater does not rise up, either there is a hot water faucet open in the system or there is a crack or hole in the tank which does not allow the pressure to build up.
  • If the pressure holds up for a prolonged period of time of about 10 to 15 minutes, then that means the tank is not leaking.

The typical design of a water heater tank is simply having convex top heads and concave bottoms.  Because of the excessive pressure inside the tank, the concave bottom may become flattened, or it may change to a convex or bulged shape.  This is considered to be very dangerous on gas water heaters, where the movement of the bottom could result in the deformation of the head of the tank as they are directly connected by the rigid flue.  This can cause further restriction of the products of combustion from venting through the flue passage and out the chimney.

By means of simply looking into the combustion chamber, you can check if there is any distortion occurring at the bottom of the tank.  It is a must to replace bulging water heater tanks if they can no longer be fixed.  As a matter of fact, tank-type water heaters with a bulging condition are actually not covered by warranty due to improper installation.

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