What t and P valve means
The T and P valve on a water heater opens to release water if the tank gets too hot or the pressure too high, so the tank cannot burst.
Also called temperature and pressure relief valve, relief valve.
Where it matters on a plumbing job
Its discharge pipe must run to a safe place and cannot be capped or reduced. On every water heater call, check the valve and the discharge line, and fix a bad discharge before it hurts someone.
What the model code says
- The relief discharge pipe terminates not more than 6 inches above the floor or receptor, and not less than two times its diameter. (IRC 2021, Chapter 28)
Check which code edition your building department enforces for t and P valve before you quote.
What it costs
The water heater installation cost guide has the typical job at $1,350 and the usual range at $890 to $2,400. The guide shows its sources and what moves the price. The water heater replacement cost calculator prices a job line by line.
Work it out
- Free calculator: Water heater replacement cost calculator
- Cost guide: Water heater installation cost
- Licensing: Plumbing license rules by state
- Tools, templates and guides: Free plumbing resources
Sources: 2021 International Residential Code, Chapter 28, Water Heaters (ICC). Checked October 9, 2026.