During the winter months, when home fires grow in frequency, heating safety is of the utmost importance. One part of your water heater plays a large role in operational safety: the Temperature and Pressure (T&P) Relief Valve.

Let's break it down. The T&P Valve is a tiny device sitting atop or just a bit below the top of a water heater. It constantly measures the heat and pressure inside your device. Think of it like a safety valve that steps in when components get too hot or too pressurized. When they do, the valve opens and lets out water to bring the system back to equilibrium. A typical T&P valve opens at a pressure of 150 psi and a temperature of 210 degrees Fahrenheit. Without a T&P Valve, your water heater could seriously injure you or your family through water damage or, in the worst case, bursting.

Sometimes, the T&P valve opens more often when the water heater lacks a thermal expansion tank. A thorough and professional examination of your water heater will give you the necessary knowledge to understand your T&P valve’s operation. Regardless of your water heater’s structure, plumbing standards require a T&P valve and proper discharge pipe, which safely channels any released hot water away from the heater, across all water heaters.

Installing and Checking the T&P Valve

Upon installation, the water heater’s T&P Valve should be properly positioned and functional. The device should be mounted either at the top or the side of your water heater apparatus and be within a 6” clearance on top. The water discharge pipe should also be safely installed and maintained. The pipe must be made of the right materials to prevent melting. PVC, for instance, is not suitable for hot water and could fail at a crucial moment as it is only cold water-rated. The only exception stands when a pipe PVC reads that it is approved for T&P valve discharge use, as denoted by a red print in most cases. Other plumbing materials, like copper, PEX, CVPC, and polybutylene (PB) can be used instead. Two of the most common issues identified during a home inspection are an incorrectly installed discharge pipe and a T&P discharge pipe that is not hot water rated. Improper discharge pipe installation, make-up or lack thereof can lead to 2nd-to-3rd degree burns from scalding. During our inspections, we always take a close look at these valves and pipes because proper installation ensures safety. A correctly installed T&P Valve is like having a good insurance policy – you hope you never need it, but it ensures maximum coverage and reduced costs when you do.

Pressure relief valves

Here are some tips to maintain a safe and operationally efficient T&P valve and discharge pipe:

  • The discharge pipe's diameter should be at least equal to that of the T&P valve outlet it's serving, generally no less than 3/4 inches, to ensure unobstructed flow.
  • From the valve to the air gap, the pipe must not reduce in size, maintaining the integrity of the pressure relief pathway.
  • To minimize strain on the valve, the discharge pipe should be as direct and as straight as possible.
  • Install the discharge pipe in a manner that allows water to drain by gravity – this ensures efficiency and safety.
  • Ensure the pipe is not trapped, as standing water can lead to contamination and a potential backflow into the drinkable water supply.
  • The end point of the discharge should be a floor drain, an indirect waste receptor, or to the outside of the building, not directly connected to the drainage system to avoid contamination of potable water.
  • Ensure the discharge creates a visible air gap in the same room as the water heater, which helps in identifying leaks and preventing backflow.
  • In regions where freezing temperatures are a concern, first route the pipe to an indirect waste receptor, like a bucket, through an air gap located in a heated space before it discharges outside. This prevents the pipe from freezing and getting blocked.
  • The pipe should terminate no more than 6 inches above the floor or the waste receptor to avoid potential hazards.
  • The discharge must be designed in a way that prevents scalding, ensuring the safety of anyone near.
  • It should also be directed in a way that avoids causing damage to the structure or property.
  • The discharge point needs to be easily visible to the occupants so any discharge can be quickly noticed, indicating that there is an issue needing attention.
  • The piping must be independent of any other equipment drains, water heater pan or relief valve discharge pipes, leading directly to the point of discharge.
  • Do not install valves anywhere within the discharge pipe, as this could prevent the necessary flow of water.
  • Avoid the use of tee fittings, denoted by their T shape and used to combine or divide flow, which could impede the water's discharge flow.
  • Lastly, the discharge pipe should not have a threaded connection at its end to prevent the possibility of it being capped, which would hinder the valve's operation.


Upon installation, know the T&P discharge pipe must be the same size, not smaller, as the T&P valve to prevent flow constriction and further pressure build-up. Without a discharge pipe, the T&P valve could shoot out scalding water, seriously injuring anyone nearby.

Your T&P Valve is a silent guardian, but even guardians need annual check-ups. We suggest testing your T&P valves annually through our Healthy Home Check, a recurring and comprehensive home inspection without the hassle and excess time required for a Full Home Inspection and report. Even if you had your T&P Valve properly checked when you bought your home, elements like this can break and deteriorate as time progresses. T&P valve testing is essential to ensure minerals and other particles don’t clog the valve’s interior or block it from proper operation.

Before calling WIN, you can test the T&P Valve lever to release a bit of water. If water doesn't come out, or if it seems to leak or drip constantly, you have a problem. This isn't just about industry compliance; it's about peace of mind, knowing your home is safe from potential water heater mishaps. T&P valves are connected to a small metal arm or tab that assists with opening. The resolution to a broken valve is to replace it entirely with the help of a licensed and qualified plumber.

Normally, a T&P valve should not drip. Small amounts of drip below the valve are typically no cause for concern, but we advise carefully monitoring the situation. Larger puddles and splashes are indications of serious inspection and repair. Typically, the solution here is to replace the T&P valve or thermal expansion tank or install a pressure regulator – depending on the structural integrity of your water heater apparatus. To ensure your health and safety along with your water heater longevity, leave the inspection and replacement process to qualified professionals only.

When we inspect homes, we pay special attention to the T&P Valve. We don't test them ourselves, but we do look to see if they exist and are in good condition. We also check the discharge pipes to ensure correct material, quality and installation. These might seem like small details, but they're big indicators of your water heater's health and safety. Ensuring these components are in order leaves you with peace-of-mind and cost savings in the long run. Remember, a little attention to the T&P Valve can go a long way in keeping your home safe.

Author Bio:

Pat Knight

A former home inspector, Pat serves as the Director of Training and Licensing for WIN Home Inspection, Pat has been in the inspection services industry for over 30 years and is an expert in performing and teaching 35+ essential services.