Gas water heaters are a bit more complex than electric-only water heaters due to the necessities of properly handling and venting the gas that powers the system. A gas water heater has a couple of different valves that relate to the safe operation of the water heater. Understanding these valves – and how each valve can malfunction – can help you quickly identify future problems and guide you in either performing the fix or informing a plumbing repairs technician about your problem.

Here are two important safety valves on a gas water heater and how each works and can malfunction.

 Gas Valve

The gas valve is the valve that opens and closes to allow a small supply of gas into the burner assembly for lighting so that there's something to heat the water in the tank. A gas valve is meant to open when triggered by signals coming from the pilot light heating a thermocouple. The valve triggers shut either when a temperature probe senses that the tank water has warmed enough or when a safety mechanism senses that something is amiss and that the gas supply needs to stop pronto.

Problems with the gas supply valve can result in the system not heating efficiently or at all. In rare cases, the valve can become stuck open and allow too much gas into the system, which can then allow that gas to leak out into your home.

If your water heater has started heating less efficiently or has stopped heating, call in a plumber as soon as possible to diagnose the problem. Turn off the gas supply to the unit using the shut-off valve until the plumber can look at the gas valve.

Pressure Relief Valve

The pressure relief valve is a safety mechanism built into the top of your hot water tank usually right next to the discharge pipe. The pressure relief valve, also called a temperature and pressure relief valve, ensures that the water heating up in the tank doesn't become too pressurized for the system's safety requirements. Too much pressure could cause the tank to explode, which would pose a safety hazard to both you and your home.

You can regularly check the pressure relief valve to make sure it's operational. Turn off all gas and electric to the water heater and then lift up the pressure relief valve. Make sure you place a bucket under the valve to catch any water the valve might let spill. If the valve makes a depressurization sound, which sounds like a hiss, and some water and steam escape from the valve, you have an operational valve.

Otherwise, you need to replace the valve. That process requires draining the tank before you or the plumber put on the new valve.