Thermal Expansion And Boiler Temperature/Pressure Valve Leaks

4 February 2016
 Categories: , Blog


Water expands when it is heated. This expansion usually causes an increase in pressure in the heating system, which if not regulated, can become a safety hazard. To regulate this increase in pressure, manufacturers fit most boilers with a pressure-reducing valve.

Under normal conditions, the pressure reducing valve is usually enough to keep the pressure increases in check. However, if something goes wrong, like a faulty thermostat, and the water expands way beyond what is expected, there is usually a more-than-normal increase in pressure in the heating system. Suddenly, the pressure-reducing valve is out of its depth. This is where a Temperature/Pressure Relief (TPR) valve steps in

A TPR valve works by providing an outlet for the excessively built-up pressure in the system. It allows any excess water, and steam, to leave the system and thus preventing any chances of ending up with a boiler explosion.

Leaking risks

However, while the TPR valve is great at taking care of this excess pressure, doing so continuously creates a safety hazard. This is because TPR valves are not designed to work continuously. That, and the fact that continuous dripping usually leaves them susceptible to getting clogged by mineral salts, which are usually left behind when the leaking water evaporates, increases the risks of Temperature/Pressure Relief Valve malfunctions.

What this means is that as a homeowner, you should be concerned when you see your Temperature/Pressure Relief valve dripping continuously. Why? Because it implies that one of your heating system's safety features has been compromised. There's also the  fact that your boiler might be having an underlying problem, like a malfunctioning thermostat, that has yet to be fixed. It is for this reason that experts usually advise homeowners to get their system checked immediately they notice that their Temperature/Pressure Relief valve is leaking.

False positives

While Temperature/Pressure Relief valve leaks are an indication of possible thermal expansion problems, not all TPR valve leaks are caused by thermal expansion complications. For example, if the TPR valve has a problem closing, due to accumulation of dirt and debris, leaks can occur.

To tell the difference between leaks caused by a faulty TPR valve and those caused by thermal expansion problems, you will need a pressure gauge. Installing it in the heating system will be able to tell you whether there are thermal expansion issues to worry about -- abnormal increases in the system pressure are a sure indication -- or if the problem lies with the TPR valve itself.

For more information, contact a company like Robinson Heating & Cooling Inc.


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