Water Heater Leaking? What to Do Right Now (and What It Means for Repair vs. Replacement)

Updated 2026-07-27 · Plumber Comparator editorial team

A puddle under the water heater triggers a specific kind of dread, but here's the reassuring truth: a leaking water heater is almost never a middle-of-the-night emergency once you've shut two valves — and where the water is coming from tells you, with surprising reliability, whether you're facing a $150 fitting repair or a full replacement. Here's the immediate response, the diagnosis, and the repair-or-replace math, in that order.

First five minutes: isolate it

• Shut off the cold water inlet. There's a valve on the cold line entering the top of the tank — turn it clockwise until it stops. This stops the tank from refilling, which stops most leaks from getting worse. If the valve is broken or absent, use the main house shutoff.
• Kill the energy. Gas: turn the control knob to OFF (or PILOT if you may relight soon). Electric: switch off the water heater's breaker — an electric element exposed by a draining tank burns out fast.
• Protect the floor and check downstream. Towels, a pan, and a look at what's below if the heater is in an attic or on an upper floor — that's where an unnoticed leak does real money damage.

With the inlet closed and energy off, the emergency is over. You now have a plumbing appointment, not a crisis — a distinction that matters at after-hours rates.

Where is it leaking from? The diagnosis is the location

• Top of the tank, at the pipe connections: usually loose or corroded inlet/outlet fittings or flex connectors. The good news category — typically $150–$400 to repair, and the tank itself is fine.
• The temperature & pressure relief (T&P) valve, on the side: a T&P valve that drips may itself be failing (a $150–$350 swap), but it may also be doing its job — relieving excess pressure from thermal expansion, a common issue on California homes with pressure regulators and check valves. Our guides on the T&P valve and expansion tanks cover both possibilities. Don't plug it, ever.
• The drain valve, near the bottom: a weeping drain valve is cheap to replace or cap ($100–$250).
• The tank body itself — water seeping from under the jacket or pooling with no fitting above it: this is the one that ends the story. The inner steel tank has rusted through, there is no repair, and replacement is the only path. How fast you need it depends only on how big the leak is.

Repair or replace: the age rule

The deciding variable is the tank's age — check the serial number on the label, which encodes the manufacture date. Under 8 years old with a fitting or valve leak: repair, and the tank may even be under warranty. Over 10–12 years old, even with a repairable leak: put the money toward replacement, because tank corrosion is cumulative — the sacrificial anode rod that protects the steel is likely spent (our anode rod guide explains why that matters), and the next failure may be the tank body at a worse moment. A standard tank replacement in California runs $1,400–$3,500 installed — see our replacement cost guide — and it's also the natural decision point for upgrading to a tankless unit or a heat pump water heater with California rebates.

Leaks in general deserve more respect than they get: the Water Research Foundation's landmark Residential End Uses of Water study (Version 2, by DeOreo, Mayer and colleagues, 2016) metered water use in thousands of North American homes and found leaks average roughly 17 gallons per household per day — about an eighth of all indoor use — with a small share of homes leaking far more, usually without knowing it (see the study via Google Scholar). A water heater that fails visibly is, in a sense, the polite failure mode; the same aging plumbing often leaks quietly elsewhere, which is why a spiking bill deserves the checkup we describe in our high water bill guide.

Getting it fixed

When you call, have three facts ready: where the water is coming from (top fittings, T&P, drain valve, or tank body), the age from the serial number, and gas or electric. Those three answers let a plumber quote most jobs over the phone. Water heater work is among the most-requested jobs on this site, from Antioch to Elk Grove to Carlsbad — describe the leak on Plumber Comparator and request a free quote, and if the tank body has gone, get replacement quotes from at least two installers before saying yes.

Keep reading

• Sewer Lateral Inspections When Selling a Home in California (East Bay PSL Rules & Compliance Costs)
• Gas Line Installation Cost in California (Stove, Dryer, BBQ, Fire Pit — and the Permit Question)
• Do You Need a Permit to Replace a Water Heater in California? (Yes — Here's What It Costs and What Inspectors Check)