Notes From The Field
06.13.2007 | PLUMBING
Watts 210
All water heaters are required to have a Temperature and Pressure Relief valve (TPR) with a properly installed drain line. Any junior home inspector knows all about this requirement! Somehow licensed plumbers don't get the concept sometimes. That still amazes me! Temperature and pressure relief valves are very important safety features for all water heaters. Think of a water heater as a giant grenade. Water stores energy and as the pressure rises, the boiling point of the water rises. If these rise too much, the tank can explode. Exploding tanks are known to have shot in the air hundreds of feet, and rock houses of their foundations. What do you do when it isn't practical to install a TPR because of the water heater location? This happens in old houses where water heaters are installed in inside utility closets, in basements, during remodels, and when no forethought was used. Luckily there is an alternative to this. It is called the Watts 210 valve.
Click photo for larger view. Watts 210 valve installed in water heater.
This is from the Watts website, "Series 210-5 Automatic Gas Shutoff Valves are used in gas water heater applications to protect against overheating water in the domestic hot water supply heating system. It is an immersion-type valve that automatically shuts off the gas supply to the heater if the temperature reaches 210°lF (99°C). It is a self-contained device that consists of Buna-N disc-to-metal seating, manual reset button to reopen the valve after an automatic shutoff, trip latch assembly and stainless steel spring seats to close the valve at a controlled temperature, and thermostat with extension tube which operates trip latch in response to water temperature." In simple terms, it is a temperature sensing device that shuts off the gas if the water in the tank is too high. It is very important to note that besides installing a Watts 210, a separate pressure relief valve must be installed. Remember, that both pressure and temperature relief is required. If you find a Watts 210, it is generally because a normal TPR could not be installed in this location. This generally has to do with installing the drain line. TPR drain lines have length limits, bend limits, and must always flow down to an approved location. When one or more of these criteria can't be achieved, the 210 valve is a good choice. Since pressure valves require a drain line you should not find one at the water heater. If so, make sure it meets the normal requirements. Since the pressure relief valve isn't at the water heater, where is it? Normally they are found outside near a hose bib. Always remember to go around the house and verify that a pressure relief valve was installed along with the Watts 210. If not, it is an improper installation.
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