Seeing water drip from your water heater’s temperature and pressure relief (T&P) valve can be unsettling—and it should get your attention. That small brass valve is a critical safety device designed to release excess temperature or pressure so your tank doesn’t become dangerous.
At A1 Best Plumbing, our Long Beach Plumbing experts recommend treating any persistent dripping as a sign to diagnose and correct the underlying cause, not just the symptom.
Quick Answer
- A T&P valve drips because your water heater is relieving excess temperature, pressure, or both.
- Common causes: thermal expansion, high water pressure, overheating from faulty thermostat/sediment, a failing T&P valve, or improper installation.
- First steps: Don’t cap the discharge pipe. Check your water temperature (target 120°F), test water pressure (aim 45–60 psi), and look for an expansion tank on the cold line.
- Fixes our Long Beach Plumbing experts recommend: install or recharge an expansion tank, set water temperature to 120°F, add/adjust a pressure-reducing valve (PRV), flush sediment, or replace the T&P valve if it’s defective.
- If the valve is flowing continuously or the tank is very hot, shut the heater off and call A1 Best Plumbing.
What the T&P Valve Does (and Why Dripping Matters)
The T&P valve is calibrated to open if water temperature exceeds roughly 210°F or pressure exceeds 150 psi. A momentary, small release can happen during heat cycles, especially in closed plumbing systems. But continuous dripping or frequent discharge indicates a system condition that needs attention. Our Long Beach Plumbing experts recommend correcting the cause promptly to protect your home, your energy bill, and your safety.
The Most Common Reasons Your T&P Valve Drips
- Thermal expansion in a closed system
- When water heats up, it expands. If you have a PRV or a check valve at the meter, your plumbing becomes a closed system and pressure can spike during heating. The T&P opens to relieve that spike.
- Fix: Install a properly sized and charged thermal expansion tank on the cold inlet.
- Excessive water pressure
- City pressure or booster pumps can push static pressure above 80 psi. Spikes during off-peak hours are common.
- Fix: Add or adjust a PRV to keep household pressure in the 45–60 psi range and include a pressure gauge for monitoring.
- Overheating from faulty controls or sediment
- A failing thermostat, stuck gas control valve, or heavy sediment buildup can cause the tank to overheat. Sediment blankets the heat source, forcing longer burn times and hotter localized temperatures.
- Fix: Flush the tank, service the burner/elements, and verify thermostat accuracy. Set temperature to 120°F.
- Aging or defective T&P valve
- T&P valves can wear out, scale up from hard water, or fail to reseat, causing a chronic drip.
- Fix: Replace the valve with the correct rating (3/4″, 150 psi, temp-rated) and proper discharge piping.
- Improper installation
- Discharge piping that is too long, upsized/downsized improperly, or sloped upward can trap water and prevent proper seating.
- Fix: Correct the piping to code: full-size, gravity fall, no valves, no caps, terminate to an approved drain at the proper height.
Our Long Beach Plumbing experts recommend assessing all of the above together—many homes have more than one contributing factor.
Safe DIY Checks Before You Call
- Verify temperature at a faucet
- Run only hot water for a minute and measure with a kitchen thermometer. Aim for 120°F. If you’re reading 130–140°F or higher, dial it down and recheck in a few hours.
- Check household water pressure
- Use a simple screw-on gauge at a hose bib or laundry tap. If static pressure is over 80 psi or swings widely, you need a PRV adjustment or replacement. Our Long Beach Plumbing experts recommend monitoring pressure at different times of day to catch spikes.
- Look for an expansion tank
- You should see a small tank on the cold line near the heater. Tap it: the top should sound hollow (air), bottom heavier (water). If it’s waterlogged or the air charge doesn’t match your house pressure, it won’t control expansion.
- Observe the drip pattern
- Drip only during heating cycles? That points to thermal expansion. Constant drip or flow? That suggests high pressure, overheating, or a failing T&P valve.
If anything looks unsafe—scorching, strong gas smell, continuous discharge—turn off power/fuel to the heater and call A1 Best Plumbing immediately.
Fixes That Actually Solve the Problem
- Install or service a thermal expansion tank
- Properly sized to your tank and water pressure, charged to your static pressure, and placed on the cold inlet. This is one of the most effective remedies our Long Beach Plumbing experts recommend for closed systems.
- Add or adjust a pressure-reducing valve (PRV)
- Keeps dynamic pressure in the sweet spot, reducing stress on fixtures and the water heater. PRVs wear out; replacement every 7–12 years is common.
- Flush sediment and service controls
- An annual flush helps in Long Beach’s mineral-rich water. On gas models, clean the burner and check combustion; on electric, inspect elements and thermostats. Our Long Beach Plumbing experts recommend descaling and adding a sediment prefilter when needed.
- Replace the T&P valve
- If the valve is old or won’t reseat after causes are addressed, replace it. Always install to code: full-size discharge line, slope downward, no traps, no shutoff, and no threaded cap on the end.
- Set the thermostat to 120°F
- This reduces scald risk, saves energy, and limits overheating events.
Long Beach–Specific Factors
- Hard water and scale
- Mineral buildup accelerates overheating issues and valve wear. Our Long Beach Plumbing experts recommend annual flushing and considering a water softener or scale-reduction system if you see frequent sediment.
- Pressure spikes
- Neighborhood pressure can swing significantly overnight. A healthy PRV and expansion control protect your plumbing—and your T&P valve—from constant stress.
- Code nuances
- California Plumbing Code requires proper T&P discharge piping and expansion control on closed systems. Earthquake strapping, drain pans with drains (where required), and proper combustion air/venting are also essential. A1 Best Plumbing ensures your system meets local code and safety standards.
What Not to Do
- Don’t cap or plug the T&P discharge line—ever.
- Don’t install a smaller line or add valves on the discharge piping.
- Don’t ignore constant dripping; it wastes energy and can mask a safety issue.
- Don’t crank water temperature up to “boost” hot water; solve the root cause (capacity, sediment, or mixing valve needs).
When a Drip Signals It’s Time to Replace the Heater
Even with the right fixes, some tanks are at the end of their life. Consider replacement if you have:
- A tank older than 10–12 years with recurring issues
- Visible corrosion around fittings or the T&P port
- Frequent overheating or discolored hot water
- A leaking tank body (unrepairable)
Our Long Beach Plumbing experts recommend comparing the cost of ongoing repairs with the benefits of a modern, efficient replacement—tankless or high-efficiency tank options may lower bills and improve performance.
FAQs
- Is a little drip normal?
- Occasional drips during heating can happen in closed systems without expansion control. Persistent dripping is not “normal” and should be addressed.
- How often should the T&P valve be replaced?
- Many manufacturers suggest inspection annually and replacement roughly every 5 years or when testing indicates sticking or leakage—sooner in hard water areas.
- Can I test the valve myself?
- Lifting the test lever can confirm operation, but it may not reseat on an old valve. Our Long Beach Plumbing experts recommend testing only if the discharge line terminates safely and you’re prepared to replace the valve if it keeps dripping.
Get Expert Help from A1 Best Plumbing
T&P valve dripping is a symptom—solving the cause protects your home and hot water system. A1 Best Plumbing diagnoses temperature, pressure, expansion, and installation issues quickly, then implements the targeted fix our Long Beach Plumbing experts recommend: expansion control, PRV adjustment, sediment service, thermostat calibration, or T&P replacement to code.Want a safe, permanent solution?
Contact A1 Best Plumbing for a same- or next-day evaluation. We’ll stop the drip, restore efficiency, and keep your water heater operating safely—so you can enjoy reliable hot water with peace of mind.