Heating and Cooling Solutions

Pressure Relief Valves

Most folks take this tiny valve for granted. They are installed on every single boiler and water heater. This brass valve is located on the top side of the boiler or water heater and has a silver lever on top. It should have a copper pipe threaded from one side that extends to the floor. Boilers and water heaters are “pressure vessels” and rated as such. The relief valve is there to prevent excessive pressure and a possible explosion from a tank rupture. Heat is applied to the water by a gas burner, electric element, or a wood fire. If this heating source were to malfunction and continue to heat the water beyond the temperature setting, an amazing amount of pressure will develop. The standard water heater relief valve opens at 150 PSI (pounds per square inch). When these valves get corroded inside, the seat will not lift and the amount of pressure it would take to open the valve is anyone’s guess. We regularly run into valves that need to be pried open after years of no attention.

However, this is not to say you shouldn’t pop the relief on your water heater or boiler; on the contrary, it is a requirement. The manufacturer’s tag states the valve MUST be opened once a year by the water heater owner. The relief valve should be inspected at least every three years by a qualified service technician. Only a small percentage of safety minded people actually have this done.

Before you go down to pop your relief valve, make sure it is piped properly. If it isn’t, it can make a big mess. The valve discharge pipe (the one coming off the side) must terminate within 6’’ of the floor and hopefully near a suitable drain. The pipe cannot get smaller in size, be longer than 30 feet, or have more than four elbows. It also cannot be threaded at the end. If you have ever experienced a relief valve opening under pressure (as I have many times) you would want to avoid that at all costs. The possibility of scalding and serious property damage is a reality. It is so easy to pipe these to the floor, but it gets forgotten many times.

If your relief valve is leaking it needs to be replaced. If it drains water occasionally, then it may be doing its job and relieving pressure. However, there is usually a reason for this and that reason should be diagnosed. There are any number of problems that will cause this and it is our job to determine the solution.

Give us a call at AirWorks if you need help, 24 hours a day, at 257-1341.

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