Water Heater Leaking from the Bottom: Causes and What to Do Next

Water pooling under your water heater is one of those problems that only gets worse. Here’s how to read the signs — and when it’s an emergency.

First: Shut Off the Water and Power

Turn the cold-water supply valve above the heater clockwise to close it. For electric heaters, switch off the breaker. For gas, turn the gas control to “pilot” or “off.” Then do not use hot water until it’s inspected.

Cause 1: Failed Drain Valve

The small spigot near the bottom can drip or stream if its washer wears out or sediment keeps it from sealing. This is the best-case scenario — a valve replacement is quick and inexpensive.

Cause 2: Leaking Temperature & Pressure (T&P) Relief Valve

The T&P valve is on the side near the top, with a discharge pipe running down. If water comes from that pipe, the tank may be overheating or over-pressurized — a safety issue, not just a nuisance. Don’t cap it; call a professional.

Cause 3: Condensation (Tankless and New Installs)

A small amount of moisture under a brand-new heater can be normal condensation as the tank heats for the first time. If it dries up within a day, you’re fine. If it keeps coming, it’s a leak.

Cause 4: Cracked Tank — the Bad One

If water seeps from the tank body itself with no valve nearby, the inner tank has likely cracked from sediment corrosion. Tanks don’t get repaired — they get replaced. The average tank lasts 8–12 years; if yours is past 10, start planning.

Repair or Replace?

• Under 8 years old + valve leak → repair.
• Over 10 years old + any tank-body leak → replace.
• Between 8–10 → depends on condition; a tech can tell in one visit.

What It Costs to Ignore

A slow leak rots the subfloor, feeds mold, and can burst into tens of gallons on the floor overnight. We’ve seen garage floods that cost more in flooring than the heater replacement would have.

Smart Repair handles water heater repair and replacement — tank and tankless, gas and electric — across Dublin, Pleasanton, San Ramon, Livermore, Danville, and nearby cities. The diagnostic visit is $80. Book online or call (510) 283-8087.