Water heater leaking from the bottom? Here's what to do.

You walk into the garage or the utility closet and there's water on the floor around the water heater. That sinking feeling hits. "Is this going to be expensive?"

The honest answer: it depends on where the water is coming from. Some leaks are a valve or a fitting, a repair priced in the hundreds. Others mean the tank is done. The good news is that you can usually narrow it down yourself before calling anyone.

We've been inside thousands of homes across Orange County, and water heater leaks are one of the most common calls we get. Let's walk through what to do right now, what's actually causing the leak, and when you need to pick up the phone.

Step one: don't panic, but don't ignore it.

Before you grab a flashlight and start investigating, handle these two things first. They take about 30 seconds and they keep a manageable situation from getting worse.

Turn off the power. For a gas water heater, turn the gas valve to "off" or "pilot." For an electric unit, flip the breaker at your electrical panel. You don't want the unit trying to heat water while it's leaking.

Shut off the cold water supply. There's a valve on the cold water line going into the top of the water heater. Turn it clockwise. This stops more water from feeding the leak.

Once those two things are done, you've bought yourself time to assess the situation calmly. Soak up the water that's already on the floor with towels or a wet vac, and move boxes and anything else that wicks moisture away from the unit.

Where exactly is the leak? A diagnostic guide.

The single most important question is where the water is coming from. That tells you almost everything about what's going on and what it's going to take to fix it.

Expert Tip

Wipe the area completely dry with towels. Lay down paper towels or newspaper around and under the water heater. Check back in an hour or two. The wet spot on the paper will tell you exactly where the water is coming from. This simple trick saves a lot of guesswork.

Bottom: the drain valve

Every water heater has a drain valve near the bottom. It looks like a small spigot or hose bib. It's used for flushing and maintenance, but over time the valve can develop a slow drip. This is especially common if the valve hasn't been opened in years and sediment has built up around the seal.

What to look for: Water dripping directly from the valve itself, not from the tank around it.

What it means: This is usually a repair, not a replacement. The valve can be tightened or swapped out. We quote it after the diagnostic, once we've seen the valve and the tank around it.

Bottom: the tank body itself

This is the one nobody wants to hear. If water is seeping from the bottom of the tank body, not from the drain valve or any fitting, the steel has corroded from the inside out. There's no patching this. The tank has reached the end of its life and needs to be replaced.

What to look for: Water appearing along the base of the tank, coming from the steel itself rather than any visible valve or connection.

What it means: The anode rod that protects the tank interior has been fully consumed. Without that sacrificial rod, the tank walls corrode. We see this most often in older units that have gone years without maintenance.

If this is your situation, it's time for a new water heater installation. A standard 40 to 75 gallon tank, installed with the old unit hauled away, runs $2,299 to $4,849. Power-vent and heat pump units run higher. This might also be a good time to weigh tank versus tankless. A condensing tankless system runs $5,999 to $8,999 installed.

The pressure relief valve (T&P valve)

The T&P valve is a safety device on the top or upper side of the tank. It has a discharge pipe that runs down the side of the tank toward the floor. If you see water at the base of the water heater, trace it upward. It might be coming from this discharge pipe, not the tank itself. That's a very different repair.

An occasional drip from the discharge pipe as the tank heats usually points to thermal expansion, the pressure an expansion tank is there to absorb.

Steady dripping or a flow is the valve telling you something needs attention. It could mean:

• The valve is worn and needs to be replaced
• The water temperature is set too high (check the thermostat, it should be around 120 degrees)
• The water pressure in your home is too high
• The thermal expansion tank has stopped doing its job (more on this below)

Supply line connections at the top

The cold water inlet and hot water outlet connect to the top of the water heater. Over time, fittings can loosen or corrode. You'll see water dripping down from the pipe connections at the top of the unit, and it can run down the jacket and pool at the bottom.

What to look for: Moisture, corrosion, or dripping where the pipes meet the water heater.

What it means: Sometimes tightening the connection is enough. If the fitting is corroded, it needs to be replaced, and that's a routine water heater repair.

The expansion tank

If your home has a closed plumbing system, and many newer homes in Orange County do, you should have a thermal expansion tank installed near the water heater. When that tank stops working, the extra pressure has nowhere to go, and it shows up as water at the T&P valve or at other fittings.

Closed systems are common in neighborhoods built in the 1990s and 2000s, in places like Aliso Viejo, Rancho Santa Margarita, and Ladera Ranch. If your T&P valve keeps releasing water, the expansion tank is one of the first things we check. We explain how they work in our guide to water heater expansion tanks.

Why water heaters leak.

Now that you know where to look, here's why these leaks happen in the first place.

Sediment buildup

Orange County water runs roughly 8 to 19 grains per gallon depending on your water district, which is firmly in the hard water range. Over time, minerals settle at the bottom of the tank and form a layer of sediment. That layer sits between the burner and the water, so the steel underneath overheats. Years of that weakens the metal.

This is why we recommend flushing a tank water heater once a year. A tank flush runs $259 and removes the sediment before it has a chance to do real damage. Most homeowners don't think about it until the leak shows up.

Internal corrosion (a spent anode rod)

The anode rod is designed to corrode instead of the tank, buying you years of extra life. But once the rod is used up and nobody replaces it, the tank is on borrowed time. Hard water wears anode rods down faster.

Replacing an anode rod runs $376 to $730, depending on whether it's a standard rod or a powered upgrade. That's a fraction of the cost of a new water heater, and it's one of the best things you can do for the life of the tank.

High water pressure

If your home's water pressure is above 80 PSI, it puts extra stress on every part of the water heater, especially the T&P valve and the supply connections. High pressure is sneaky because you might not notice it until something starts leaking. A plumber can test it in a couple of minutes.

Age

A tank water heater typically lasts 8 to 12 years. Without maintenance, expect the shorter end of that range. If your water heater is older than 10 years and starting to leak, it's worth having a conversation about replacement rather than repair. Our guide to the signs your water heater is going bad covers how to read the clues.

Is a leaking water heater dangerous?

This is one of the most common questions we hear, so let's answer it directly.

A slow drip from a valve or fitting is not immediately dangerous. But it shouldn't be ignored. Here's why.

Water damage adds up fast. A slow leak soaks into flooring, drywall, and anything stored nearby long before it looks dramatic. Insurance policies also tend to treat a sudden failure and a slow leak differently, so it's worth asking your insurer how yours handles a water heater before you ever need to file. If a leak has already damaged part of your home, here is how we help with plumbing insurance claims.

Gas water heater leaks can be more serious. If you smell gas near the water heater, or the burner is behaving strangely along with a leak, treat it as an emergency. Don't try to fix anything yourself.

Electric water heaters carry electrical risk. Water pooling at the base of an electric water heater can reach the wiring or the electrical connections. If you see standing water and you have an electric unit, shut off the breaker first, then call for help.

When you can wait and when to call now.

Not every water heater leak is a drop-everything emergency. Here's how to tell the difference.

Call during business hours

• A slow drip from the drain valve
• An occasional drip from the T&P discharge pipe
• Moisture at a supply line fitting
• Condensation on the outside of the tank (not actually a leak, more on this below)

Call now

• An active leak from the tank body itself. This won't stop on its own, and every hour means more water damage.
• A T&P valve that keeps discharging water. Something is pushing the pressure or the temperature too high.
• Water near electrical connections or wiring.
• You're not sure where the water is coming from and it's getting worse.

Emergency: call immediately

• Any leak combined with a gas smell. Get outside first.
• The water heater has ruptured or burst. Shut off the water to the house if you can reach the main, and call our emergency plumbing line.
• A large volume of water spreading toward living areas or electrical panels.

Condensation: the leak that isn't a leak.

One thing we see fairly often, especially during cooler months, is condensation on the outside of the tank. When cold water fills the tank and the surrounding air is warm, moisture forms on the surface and drips to the floor. It looks exactly like a leak, but it's completely normal.

This is more common with water heaters that have just been installed, or when the cold water supply is especially cold. It usually goes away on its own once the tank reaches full temperature.

If you've dried everything off and the water comes back slowly and evenly across the bottom, especially in the morning, condensation is the likely cause. No repair needed.

The drip pan conversation.

Here's something we bring up with every homeowner, especially during replacements. A water heater drip pan is a shallow metal pan that sits under the unit and catches small leaks before they reach your floor.

If your water heater is in the garage on a concrete floor, a slow leak is annoying but contained. But if your unit is in a closet, on an upper floor, or anywhere near finished flooring, drywall, or stored belongings, a drip pan with a drain line is one of the smartest additions you can make.

What a drip pan costs varies with the unit, where it sits, and whether a drain line has to be run. The simplest time to add one is during a new installation, when the pan goes in under the unit as it's set.

What repair or replacement costs.

Here's the quick picture, from our current price book. For the wider view, we keep a full breakdown of water heater repair costs.

Every repair is quoted up front, before any work starts. If the tank itself has corroded through, this is a good time to weigh your options. You can compare the pros and cons of tank versus tankless to see what fits your home and budget.

How to prevent future leaks.

Most water heater leaks are preventable with basic maintenance. Here's what keeps your system healthy:

1. Flush the tank once a year. It removes the sediment that causes overheating and corrosion.
2. Check the anode rod every 3 to 5 years. This is the single most effective way to extend your water heater's life.
3. Test the T&P valve once a year. Lift the lever briefly and let it snap back. You should hear water release into the discharge pipe. If nothing happens, or the valve keeps dripping afterward, have it replaced.
4. Keep an eye on your water pressure. If it's consistently above 80 PSI, talk to your plumber about a pressure reducing valve.
5. Consider a water softener. With hard water, a water treatment system lightens the mineral load on your water heater and every other fixture in your home.
6. Schedule an annual inspection. A plumbing inspection catches small issues before they become leaks.

Expert Tip

Put a reminder on your calendar for an annual water heater flush. Pick the same month each year, maybe when you change your furnace filter or check your smoke detectors. The homeowners who do this consistently are the ones who get the most years out of their water heaters.

A dripping drain valve is a repair. T&P valve discharge is usually straightforward. Even supply line fittings are routine work. The one situation where repair won't help is when the tank body itself has corroded through. If that's where you are, it's time for a conversation about what comes next, and we're happy to walk you through the options.

Water has a way of showing you where it wants to go. Most plumbing problems start small, and the families who catch things early are the ones who spend less and stress less.

If you've got water around your water heater and you're not sure what's going on, give us a call at (949) 328-6002 or schedule a visit. We'll come out, trace it to the source, and give you an honest answer. That's what we're here for.

Written by Eric Olson, Licensed C-36 Plumbing Contractor, Olson Superior Plumbing, Orange County, CA. Prices come from Olson Superior's current price book, November 2026.