Without an expansion tank linked to the water heater, any closed plumbing system can undergo severe damage due to thermal expansion.įor instance, when you heat water from 50 to 120 degrees Fahrenheit, its volume rises by about 2%. We all know that water expands when it’s heated. How an Expansion Tank WorksĪn expansion tank is required in certain circumstances and can help a water heater last longer. This article will explore where an expansion tank is installed and how to manage an installation by yourself. A water heater expansion tank is a small air-filled tank that acts as an expansion chamber to control increased water volume created as water is heated and expands. However, they can be installed inverted or on their side, provided it is strapped for support. Generally, expansion tanks are installed in an upright position. In most cases, most local plumbing codes must install an expansion tank when you install a new water heater on the municipal water supply.Įxpansion tanks are installed on the cold water pipe above the water heater. An expansion tank is a safety device installed on a heating system to protect fixtures and pipes in a plumbing system not fitted with a backflow preventer or check valve. The above does not only apply to areas with extremely high main distribution water pressure, but will also occur in areas where the utility will require a check valve in front of the water meter, or where codes require backflow prevention devices installed in the water service.Even before we look at where expansion tanks are installed and whether it is on a hot or cold line, we need to understand what the tank involves. Or, if codes require a back flow prevention device a properly sized thermal expansion tank should be installed in the supply side piping of the water heater. This will permit the water to expand back into the main supply when heated. Replace the water inlet pressure reducing valve with a valve that has a back flow by-pass built into it. Where a temperature and pressure relief valve is used on a water heater installation, as described above, every time the water heater cycles on the relief valve will discharge or drip. Under these conditions the tank would be subject to a minimum of 240 PSI with a 60 degree rise in water temperature (4 x 60 = 240) and minimum 400 PSI with a 100 degree rise in water temperature (4 x 100 = 400) and since the tank is designed to withstand a test pressure of 300 PSI, it can be easily understood that the tank may very well rupture unless a temperature and pressure relief valve is installed in the water heater. In the case where the reducing valve does not permit back flow, we have found by tests that for every degree rise in the temperature there is a build up of pressure from 4 to 6 pounds per square inch in the water heater tank. These reducing valves are available with or without a back flow check. Contractors are installing water pressure reducing valves in the service. More and more housing developments are being constructed in areas where the local water utility is supplying these projects with extremely high water main distribution pressure. Model(s) Affected: All Residential & Commercial Units Right Spec ® Sizing & Cross Reference Tools.
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