Technical Foundation
What Is a Temperature and Pressure Relief Valve?
A T&P relief valve is a dual-sensing safety device required on virtually every residential and commercial water heater and low-pressure hot water boiler. A spring-loaded pressure disc opens when tank pressure exceeds the valve's set pressure (commonly 150 psi for residential units), while a separate thermostatic sensing element extending into the tank opens the valve when water temperature exceeds its set point (commonly 210°F) — either condition alone is enough to trigger discharge, since an uncontrolled tank can fail from excess pressure, excess temperature (which flashes to steam), or both.
Valves are manufactured and tested to ASME standards (ASME CSD-1 and the Boiler and Pressure Vessel Code, Section IV) and must be sized and set to match the tank's maximum allowable working pressure — a valve set higher than the tank rating provides no protection, and one set too low will nuisance-trip. Shank length matters on tank-top valves: the thermostatic sensing element must reach into the hottest part of the water column, so a shank too short for the tank well gives a delayed or false temperature reading.
Prefer a quick quote?
Get Temperature and Pressure Relief Valves Pricing in Your Inbox
Skip the search — tell us the set pressure, temperature setting and connection size and we will come back with pricing.
| Spec | What It Means | Why It Matters |
|---|---|---|
| Set Pressure | Commonly 150 psi residential, up to 300 psi commercial | Must not exceed the tank's maximum allowable working pressure (MAWP) |
| Set Temperature | Commonly 210°F (99°C) | Opens before stored water can flash to steam if a thermostat fails |
| Connection Size | 3/4 in. NPT most common, up to 1-1/4 in. commercial | Must match the tank's tapped T&P port, not the supply piping size |
| Shank Length | Standard vs. extended shank | Sensing element must reach into the tank's hottest water zone for accurate response |
| Certification | ASME rated, CSD-1 compliant | Required by plumbing code for connection to any water heater or low-pressure boiler |
Shop Temperature and Pressure Relief Valves
Browse Temperature and Pressure Relief Valves Sub-Categories
Organised by application and shank style. Pick a sub-category, or tell us the tank type and required set point.
How it works
From Half-Remembered Part Number to PO, in Three Steps.
Ask
Type an MPN, paste a spec sheet, or describe the part in plain English. ChatMRO understands engineer-speak.
Compare
Side-by-side specs, cross-references, and equivalents from multiple sources — without the clutter of endless browser tabs.
Quote & Buy
Request a quote or add to cart. Volume discounts, VAT-aware pricing, and consolidated procurement — all in one place.
Applications
Where Temperature and Pressure Relief Valves Get Used
T&P relief valves are required by code on any closed water heating vessel where uncontrolled pressure or temperature buildup could cause tank rupture.
Residential Water Heater Installation
Code-required safety valve on every gas, electric and hybrid residential storage water heater tank.
Commercial & Multi-Family Water Heating
Higher-capacity T&P valves sized for commercial storage tanks and recirculating hot water systems.
Low-Pressure Hot Water Boilers
Protecting hydronic heating boilers from over-pressure or over-temperature conditions per ASME CSD-1.
Solar Thermal Water Heating Systems
Relief protection on storage tanks subject to stagnation over-temperature during periods of no draw-off.
Tankless & Point-of-Use Water Heater Retrofits
T&P valve replacement during storage tank retrofits and code-compliance upgrades.
Plumbing & Mechanical Contracting
Standard replacement stock for water heater service calls and new installation rough-ins.
FAQ
Temperature and Pressure Relief Valves Questions, Answered
Why does a water heater need both a temperature and pressure relief function?
A tank can fail two different ways: excess pressure from thermal expansion in a closed system, or runaway temperature from a stuck thermostat that lets stored water flash to steam. A T&P valve combines a pressure-sensing spring disc with a separate thermostatic sensing element so either dangerous condition alone triggers discharge, independent of the other.
What set pressure and temperature should I use for a residential water heater?
Standard residential T&P valves are set to open at 150 psi and 210°F, matching the typical maximum allowable working pressure of residential storage tanks. Always confirm against the specific tank's data plate rating — never install a valve rated above the tank's MAWP.
What's the difference between a standard and extended shank T&P valve?
The shank is the length of the thermostatic sensing element that extends down into the tank. Extended shank valves reach further into the tank well so the sensor sits in the hottest water zone on tanks with a deeper T&P tapping; a standard shank on the wrong tank well can give a delayed temperature response.
Can I use a pressure-only or temperature-only relief valve instead?
Most plumbing codes require a combination T&P valve on storage water heaters specifically because either failure mode needs independent protection. Pressure-only or temperature-only valves are used only in specific engineered systems where the other condition is protected by a separate device — check local code before substituting.
How often should a T&P valve be tested or replaced?
Most manufacturers and plumbing codes recommend testing the valve annually by lifting the test lever to confirm it opens and reseats cleanly, and replacing the valve every 3-5 years or immediately if it fails to reseat, leaks continuously, or shows mineral scale buildup that could prevent proper operation.
Keep browsing
Related Categories
Explore More
Find Your Next Part Now.
Describe a part number, spec or what it does.