Water Heater T&P Relief Valve (Temperature & Pressure Relief Valve) 101

More Background About T&P Relief Valves:

• This safety feature “[…] was designed as an emergency relief device only.” Operating a water heater without an additional protectorate from thermal expansion such as a thermal expansion tank, “the T&P valve could be subject to reduced effectiveness or failure”
• Most water heater manufacturers and local plumbing codes not only require the installation of a thermal expansion tank, but also a discharge pipe/Temperature and Pressure Relief Drain Line: a copper line that is meant to guide any discharge water from the water heater down towards the ground, ideally near a floor drain.

Does my water heater have a T&P Relief Valve?

Regardless of whether you purchase your water heater at a local hardware store, from a plumbing supplier, or directly from the manufacturer, you will likely see a note in the listing and/or on the box itself that says the water heater has a pre-installed T&P Relief Valve. This means that the water heater comes with a T&P Valve that is installed in the side of the tank, however, your installer will need to add the discharge pipe. In other words, yes, your water heater has a Temperature and Pressure Relief Valve (TPR); if your tank type water heater does not have a TPR, your water heater should not be run until an appropriately sized TPR has been installed by a professional due to the potential safety risk of excessive temperature and pressure.

Where is the T&P Relief Valve Located on a Water Heater?

The location of your water heater's T&P relief valve may vary based on the water heater's grade (residential vs. commercial) and specific model. Across most water heater manufacturers, these are the most common locations for T&P valves:

• Residential Water Heaters: The T&P valve is located on the right side; for select electric water heater models the T&P valve may be located on the top of the unit in the center (see image slider)
• Commercial Water Heaters: The location of the T&P valve varies for commercial water heaters. Many commercial standard atmospheric water heaters and electric water heaters most often have a T&P valve located on the right side of the unit, while commercial power vents tend to have their T&P valve on the left side.

Why is Protection from Thermal Expansion Important?

Thermal expansion refers to the process of water's volume and contained pressure increasing as a result of the water heating process.

“Thermal expansion of water, if not compensated for in system design, will lead to the early failure of components. These failures are not covered by the manufacturer’s warranty, so it is extremely important that everyone be aware of the causes, symptoms and solutions to thermal expansion in a closed water heating system” (Source: A.O. Smith)

Additionally, excessive thermal expansion can also be a safety hazard (Source: Rheem).

T&P Relief Valve Maintenance / TPR Inspection

Leaking T&P Valve, Discharging T&P Valve

The most common T&P Valve issue we see is leaking or discharging T&P valves. 

• "Discharge from a T&P valve may indicate an unsafe temperature or pressure condition exists, which requires immediate attention by a qualified service technician or licensed plumbing contractor" (Source: Watts).
  

Potential Cause: Thermal Expansion

The most common cause of a leaking T&P Valve or dripping T&P Valve is an increase in thermal expansion. This is most often the result of not having a thermal expansion tank installed on your water heater's cold inlet line; if you already have a thermal expansion tank and have excessive water pressure, a technician will perform a pressure test to determine whether your T&P Valve is faulty or if you may need a Pressure Reducing Valve installed to control the water pressure in your home.



Potential Cause: Faulty T&P Valve

In some cases, T&P Valves may be faulty coming directly from the manufacturer. Permitted the technician is able to determine the T&P Valve did not fail due to: user error (i.e., being forced open), high incoming water pressure, thermal expansion, or another plumbing issue, most manufacturer warranties for labor and parts will cover the cost of the replacement T&P Relief Valve and the installation (if your water heater still has labor coverage).

Why is Protection from Thermal Expansion Important?

Thermal expansion refers to the process of water's volume and contained pressure increasing as a result of the water heating process.

“Thermal expansion of water, if not compensated for in system design, will lead to the early failure of components. These failures are not covered by the manufacturer’s warranty, so it is extremely important that everyone be aware of the causes, symptoms and solutions to thermal expansion in a closed water heating system” (Source: A.O. Smith)

T&P Valve Won't Close: I Opened the T&P Valve to Relieve It and Now It Won't Close

The T&P Valve is made to open by force to relieve excess temperature/pressure inside your water heater or manually during inspection. Typically, if you should lift the T&P Relief Valve handle/lever at a 90 degree angle for maintenance, you should be able to lower it back down easily into the closed position. If the T&P Valve's lever will not close fully, it will need to be replaced. This type of T&P Valve replacement will likely not be covered by the manufacturer's warranty.

T&P Relief Valve Sizing: Are T&P Relief Valves interchangeable?

T&P Relief Valves are not all interchangeable because there are different sizes and diameters.

It is recommended to replace your T&P Valve with the replacement part number provided by your water heater's manufacturer. However, given the fact that most major water heater manufacturers use T&P Relief Valves manufactured by Watts, some part numbers are interchangeable between manufacturers.

If you are going to replace your Relief Valve without using your water heater manufacturer's direct replacement, you should be sure to match the following:

• Diameter
• BTU Ratings
• PSI Rating
• Temperature Rating
• Temperature Sensor Length
• Length of Relief Valve Body (brass portion)
• ANSI Z21.22 Relief Valves

Is T&P Valve Replacement Covered Under Warranty?

Some T&P Valve Replacements are covered under warranty.

Whether T&P Valve Replacement will be covered by warranty is determined by your manufacturer's warranty policy. In most cases, the water heater manufacturers will require some readings and documentation prior to approving a warranty T&P Valve replacement, including but not limited to:

• Installed thermal expansion tank
• Water pressure check to see if a pressure reducing valve is necessary 

If your replacement T&P Valve is not covered under warranty, you can expect to spend anywhere from about $20.00 to $75.00, depending on whether your water heater is residential (typically cheaper) or commercial (typically more expensive).

How much do replacement T&P Valves cost? / Are replacement T&P Valves expensive?

Some T&P Valve Replacements are covered under warranty.

Whether T&P Valve Replacement will be covered by warranty is determined by your manufacturer's warranty policy. In most cases, the water heater manufacturers will require some readings and documentation prior to approving a warranty T&P Valve replacement, including but not limited to:

• Installed thermal expansion tank
• Water pressure check to see if a pressure reducing valve is necessary 

If your replacement T&P Valve is not covered under warranty, you can expect to spend anywhere from about $20.00 to $75.00, depending on whether your water heater is residential (typically cheaper) or commercial (typically more expensive).

Our team of experienced water heater parts experts is happy to help! Identifying the correct replacement T&P Relief Valve for your water heater can be difficult without the right tools.

Here's What We'll Need from You:

• Your water heater's model number
• Your water heater's serial number
• OPTIONAL: Photos of your T&P Valve

Please Note: Although our Parts Department team members are experienced, they cannot diagnose issues with your T&P Relief Valve via e-mail or by phone. If you need assistance with diagnostics, we recommend contacting your water heater manufacturer's technical support first or requesting a service call.

Contact our Parts Department:

• Phone: (224)-275-5697
• E-mail: parts@uswhpro.com

Parts Department Hours:

Monday-Friday from 7:00 am-5:00 pm