Protecting Your Water Heater From Temperature Fluctuation

Protect your water heater from temperature fluctuation as very high temperatures can result in damage to the tank. In any given closed water system, a pressure regulator is installed called a TPRV or TPR valve (temperature pressure regulator valve or temperature pressure relief).

Heat Causes Expansion

Not only does the water in a tank heat, but so does the tank itself. Water expands at a higher rate than the material from which the tank is made, like steel. The result of water expansion is that the storage tank will bulge.


The water heater TPR valve opens when it detects pressure or temperature rising above a safe level. The TPR operates a venting system that diverts pressure when there is a dangerous rise. The pressure will then vent harmlessly, but with a little mess.

This valve is important, and if it becomes damaged, excessively high pressure inside the heater could cause the tank to explode. This TPR valve, also known as a pressure relief valve, is required by law almost everywhere because it is a necessary safety device operating both commercial and domestic water heating systems.

Setting the Temperature

Higher set temperatures can cause an excessive pressure buildup even though the water heater has a functional TPR or PRV. These valves allow for the outlet of dangerous pressure buildups, but venting steamy water vapor can cause damage to the surrounding area or, at best, create a mess.

Keeping the water heater at a recommended lower setting can help reduce the amount of pressurized water vapor release. A recommended setting is 120 degrees, although some experts say a lower setting at 113 degrees can meet most domestic hot water requirements.


Although the idea behind a pressure relief valve is to provide an outlet for dangerous pressure, enough force created by pressure is needed to propel water through the building’s piping system. Once a tap is opened in a home, it’s the pressure within the system that allows the water to flow.

However, very high pressure could cause an explosion. Also, high pressure running through the system can cause damage to other devices connected. Pressure can cause increased water flow that can surprise someone turning on a tap or damage a shower head.

Laws dictate that liquids and gasses be regulated by relief valves so if pressure does build up, it doesn’t blow through the system. Instead, it is safely released through a venting process that reduces the overall system pressure, preventing any damage or personal injury.

Calibrated Heater Relief Valves

In a hot water heater, the valve regulates according to both temperature and pressure. Increased temperature will increase water pressure inside the tank. However, maintaining water temperature by opening a tap allows for the pressure to build up in the tank.

A TPRV will release water when the temperature or pressure gets too high. There is a lever on the heater to test if the release system is working.