The Intelligence Behind Every Service Call.

Not yet. A dripping T&P is usually a symptom, not the cause. Find out why it's opening, or the new valve will drip too.

What I see in the photo (visible vs. suspected):

• Tank-type water heater, dated 8/23/2020, seismic strap in place.
• Side-mounted brass T&P with copper discharge line.
• Green corrosion and mineral streaks run down the outside of the copper from the threaded adapter under the valve outlet.
• Suspected: the streaks could come from the threaded joint weeping, not just from water passing through the valve. Confirm which it is first.

Diagnose before swapping:

1. Find the drip source. Dry everything off and watch. Is water coming out the end of the discharge pipe (valve opening), or seeping at the adapter threads (joint leak)?
2. Static pressure. Put a gauge with a lazy/max needle on a hose bib.
   • Normal is 40–80 psi.
   • Over 80 psi: install or service the PRV.
3. Thermal expansion. Leave the gauge on through a heating cycle or overnight.
   • A climb toward 120–150 psi means a closed system (PRV, check valve, or backflow device present).
   • Fix: install or replace the expansion tank and set its precharge to house static pressure. If one exists, check that it isn't waterlogged (water at the Schrader valve means it's failed).
4. Temperature. Check the thermostat setting (~120°F typical). Water near 210°F means a control or thermostat fault. Treat that as a serious hazard and fix it before anything else.
5. Seat debris. If the valve was recently test-lifted, sediment may be holding it open. Flicking the lever a couple of times sometimes reseats it, but a 4–5 year old valve is due for replacement anyway.

If replacing:

• Shut off gas (pilot/valve to OFF) or lock out electric. Close the cold supply and open a hot tap to relieve pressure.
• Drain the tank below the T&P opening. Scald risk: let it cool or use gloves.
• Match the rating: 150 psi / 210°F, BTU/kW rating ≥ heater input, and the correct probe length.
• Use pipe dope or tape on the tank threads only. Don't overtighten.
• Discharge line rules:
  • Full valve size.
  • No valves, caps or reductions.
  • Gravity drain.
  • Unthreaded end terminating about 6" above the floor or to an approved location, per local code.
• Clean up or redo the corroded adapter joint while you're in there.

Never plug, cap or restrict a T&P to stop a drip.

That's your problem. 95 psi static is too high, and with no expansion tank, thermal expansion is pushing it well past the T&P's 150 psi setpoint. Swapping the valve alone won't fix it.

Why it drips:

• 95 psi is over the 80 psi max most codes allow.
• When the heater fires, expanding water has nowhere to go. Pressure spikes, the T&P lifts, and it drips.
• Long-term, this also stresses the tank, fixtures, supply lines and toilet fill valves.

Fix, in this order:

1. Check for a PRV (bell-shaped valve near the main shutoff or meter).
   • None: install one. It's required by code when street pressure is over 80 psi.
   • Present: it's failed or set wrong. Adjust it, or rebuild/replace it if it won't hold. A PRV older than 10 years, or one where pressure creeps up overnight, is usually shot.
   • Set to 50–60 psi.
2. Install a thermal expansion tank. A PRV makes the system closed, so one is required.
   • Size it for the tank volume and house pressure. A 40–50 gal heater at 60 psi is typically a 2-gal tank. Check the manufacturer's chart.
   • Precharge it to match the new static pressure (e.g., 60 psi) *before* installing. Use a tire gauge on the Schrader valve with the tank unpressurized.
   • Install it on the cold supply, supported (don't let the pipe carry its weight).
3. Replace the T&P. It's lifted repeatedly and likely has a fouled seat. Use a 150 psi / 210°F valve with a BTU rating ≥ heater input. Redo the corroded adapter while you're there.
4. Verify: leave a max-needle gauge on overnight. Static should stay steady near the set point, with only a few psi rise during heating.

Safety:

• Gas OFF or electric locked out, cold supply closed, and pressure relieved before you open anything.
• Hot water scald risk when draining.
• Check whether local code requires a permit for PRV or expansion tank work.

Tell the customer: high pressure is also wearing out everything else in the house. This is a whole-house fix, not just a water heater fix.