Quick Answer
A leaking water heater relief valve is usually not an emergency, but it can become dangerous if ignored.
The most common cause is high water pressure (40% of cases), followed by thermal expansion and a worn-out valve.
7 Common Causes
1. Excessive Water Pressure (Most Common – 40% of cases)
How to diagnose:
Check pressure gauge on your plumbing system
Normal: 40–80 PSI
High: 80+ PSI → causes relief valve to open
How to fix:
Install a pressure reducing valve (PRV) on the main water line.
Cost:
Professional: $150–300
DIY: $50–80
2. Thermal Expansion
What it is:
Water expands when heated. In a closed plumbing system without an expansion tank, pressure spikes and forces the relief valve open.
How to fix:
Install a thermal expansion tank.
Cost:
Professional: $200–400
DIY: $50–100
3. Faulty Pressure Relief Valve (20% of cases)
How to test your valve
Turn off heater
Let water cool for 2 hours
Lift the test lever
Lever should snap back strongly
Water should stop immediately
If it doesn’t pass the test—or is 5+ years old:
⚠️ Replace immediately for safety.
Recommended Replacement
Our Watts3/4″PressureReliefValve–PRODUCTLINKWatts 3/4″ Pressure Relief Valve is:
ASME certified
USA-made
Backed by 5-year warranty
Installs in 30 minutes
Cost to replace:
DIY: $20–30
Professional: $150–300
4. High Water Temperature
Issue:
Thermostat set too high (above 130°F) → overheating → valve leaking
How to fix:
Turn off power
Remove access panel
Set thermostat to 120°F
Replace cover
Restore power
Why 120°F is recommended:
Prevents scalding
Reduces pressure
Saves energy
5. Sediment Buildup in Tank
What happens:
Sediment at the bottom reduces water volume → overheating + excess pressure → valve leaks.
How to fix:
Regularly flush the tank.
Frequency:
Every 6–12 months.
6. Wrong Valve Size (Rare but Dangerous)
Problem:
Undersized valves cannot handle your heater’s BTU/pressure rating.
Check your valve:
Stamped rating on body
Residential standard: 150 PSI
If you see 125 PSI or unmarked valves:
🔧 Upgrade immediately:
Watts3/4″PressureReliefValve–PRODUCTLINKWatts 3/4″ Pressure Relief Valve
7. Improper Installation
Common mistakes:
Valve installed horizontally
No discharge pipe
Discharge pipe pointing up
Wrong thread sealant
Emergency: How to Stop the Leak Temporarily
If your valve is dripping heavily or spraying:
Turn off water heater
Gas: Set to Pilot
Electric: Turn off breaker
Shut off cold water to heater
Open hot faucet to relieve pressure
Place bucket under valve
⚠️ NEVER plug or cap the valve. It can cause an explosion.
Call a plumber if:
Continuous flow (not just dripping)
Very hot water is leaking
You smell gas
You’re uncomfortable with DIY
How to Replace the Relief Valve (DIY)
Difficulty: Moderate
Time: 30–45 minutes
Cost: $20–30
Tools Needed:
Pipe wrench
Teflon tape
Bucket
Towel
Steps
Turn off heater + water supply
Drain 2–3 gallons from tank
Unscrew old valve
Wrap threads with Teflon tape
Install new valve
Tighten with wrench
Reconnect discharge pipe
Turn water back on
Test for leaks
Recommended Valve
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ASME certified
Lead-free brass
5-year warranty
Free shipping over $50
Prevention Tips
✔ 1. Test valve annually
Lift lever once per year.
✔ 2. Install thermal expansion tank
Prevents 90% of pressure spikes.
✔ 3. Monitor water pressure
Keep below 80 PSI.
✔ 4. Replace valve every 5–7 years
Even if working.
✔ 5. Flush tank annually
Reduces sediment.
Cost Summary
| Issue | DIY Cost | Pro Cost |
|---|---|---|
| Faulty valve | $20–30 | $150–300 |
| Expansion tank | $50–100 | $200–400 |
| PRV install | $50–80 | $150–300 |
| Tank flush | $0 | $80–150 |
Total prevention:
DIY: $70–210
Professional: $380–850
Potential water damage if ignored:
💸 $3,000–$10,000+
🛒 Shop quality relief valves:
👉 Watts3/4″PressureReliefValve–PRODUCTLINKWatts 3/4″ Pressure Relief Valve
Frequently Asked Questions
Is a dripping relief valve an emergency?
Not usually—unless it becomes a steady stream.
Can I just tighten the valve?
No. This can damage the internal mechanism.
Why does a new valve leak?
High pressure or thermal expansion—not the valve itself.
What valve brand is best?
ASME-certified models. We recommend …]Wattsvalves–PRODUCTLINK…] Watts valves – PRODUCT LINK.
Need a Replacement Valve Today?
Top Pick:
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Why homeowners trust it:
ASME certified
Lead-free brass
Industry standard
5-year warranty
Easy DIY install
