Water Heater Leaking? What to Do in the Next 10 Minutes

There’s water on the floor next to the water heater, and you don’t know yet whether it’s a drip or the start of a flood. The good news: in most cases you can stop the damage yourself in a few minutes, before anyone shows up.

This is the step-by-step for the next 10 minutes, written for homeowners standing in a basement or utility closet right now. By the end you’ll have the water and fuel off, know where the leak is coming from, and have a realistic idea of whether you’re looking at a repair or a new tank.

Minutes 0–2: Is it really the water heater?

If you smell gas (a rotten-egg odor) at any point, skip all of this: leave the house and call 911 or the gas utility from outside. Otherwise, before you shut anything off, take 30 seconds and look around. In most metro basements the water heater sits right next to the furnace, and plenty of “water heater leaks” turn out to be something else:

• The furnace condensate line or condensate pump on a high-efficiency furnace
• A humidifier drain line on the side of the furnace ductwork
• A water softener discharge hose that slipped out of the floor drain
• Sweating cold-water pipes or a brand-new tank sweating during its first heat-up

Wipe the floor dry, lay a few paper towels in a ring around the base, and watch where the wet spot comes back first.

Pro tip: Run a dry paper towel up the side of the tank and over every pipe joint above it. Water travels down the outside of the jacket, so a drip that pools at the bottom often starts at a fitting on top.

Minutes 2–4: How do I shut off the water to the tank?

Find the cold-water line coming into the top of the heater. It usually has a shutoff valve within a foot or two of the tank.

• Lever handle: turn it a quarter turn so it sits crosswise to the pipe.
• Round wheel handle: turn it clockwise until it stops. Don’t force an old one.

If there’s no valve, or it won’t close, shut off the main water to the house. Our emergency plumbing guide shows where main shutoffs usually hide in metro homes.

Next, open a hot-water faucet somewhere in the house. That releases pressure in the tank, which by itself stops most leaks at the top fittings and the relief valve.

Minutes 4–5: How do I turn off the gas or the power?

If you smell gas, stop here. Don’t touch any switches or valves. Leave the house and call 911 or the gas utility from outside.

Gas water heater: turn the knob on the gas control to Off. That’s the only gas control you need to touch; leave the valve on the gas supply line to us.

Electric water heater: shut off its breaker, usually a double-pole breaker labeled for the water heater. This matters more than people think. If an electric tank loses water with the power on, the heating elements can burn out almost immediately.

Power-vent gas water heater: turn the gas control to Off, then unplug it. Heat pump water heater: shut off the breaker or unplug it.

Minutes 5–8: Where exactly is it leaking from?

Where the water is	What it usually means	Repairable?	Planning range
T&P relief pipe on the side	Worn valve, or pressure or heat too high	Usually	$150–$350
Drain valve near the bottom	Worn or loose drain valve	Usually	$150–$350
Fittings or connectors on top	Loose or corroded connection	Usually	$200–$500
Inside the burner compartment	Possible condensation, possibly the tank	Needs a look	Diagnostic free with repair
Seeping from the tank body or base	Inner tank has rusted through	No, replace	$1,000–$2,000

Planning ranges for the Des Moines metro in 2026; your written quote depends on the equipment, access and what we find on site.

The T&P relief valve

The temperature and pressure relief valve is a safety device. When it drips, either the valve is worn or the tank is getting too hot or too pressurized, often from thermal expansion when an expansion tank is missing or waterlogged. Never cap or plug that discharge pipe. If it’s pushing out hot water continuously, the fuel should already be off and you should call.

The drain valve

If it’s dripping from the spout, check that it’s closed snug by hand. A garden hose cap screwed onto the drain valve threads will often stop a slow drip until the valve can be replaced.

Fittings on top

The short pipe nipples where water enters and leaves the tank corrode over time, especially on older steel connections. If the leak stopped once you relieved pressure, it’s probably up here.

The tank itself

If water is coming from under the jacket with nothing dripping from above, or you see rust weeping from the base, the steel tank inside has failed. No part fixes that.

Should I drain the water heater?

Drain it if the tank body is leaking or water is spreading toward finished space. If the leak is at the top or the relief valve and it stopped once the pressure came off, you can usually leave it full.

To drain: let the water cool first if you can, because it can scald. Connect a garden hose to the drain valve, run it to a floor drain, keep a hot faucet open upstairs to let air in, and open the drain valve. Sediment can slow it to a trickle; that’s common in Central Iowa’s hard water.

Pro tip: If the tank is 10 years old or more and the leak is minor, think twice before opening the drain valve. Old plastic drain valves sometimes won’t reseal after they’re opened, which can turn a small problem into a steady leak at the bottom.

How do I protect the floor and finished basement?

Use a wet-vac or towels, move boxes up off the floor, pull back any carpet edge near the tank, and check the bottom of nearby drywall. Take photos before you clean up in case you need them for insurance. Going forward, a drain pan and a leak sensor are cheap protection.

Protection	Planning range
DIY battery leak sensors	$30–$80 each
Auto shut-off valve with leak sensors, installed	$600–$1,500

Planning ranges for the Des Moines metro in 2026; your written quote depends on the equipment, access and what we find on site.

Repair or replace?

Repair makes sense when the tank itself is sound: a relief valve, drain valve or fitting on a heater with years left in it. Replacement makes sense when the tank body leaks, or when a tank past about 10 years needs anything beyond a simple part.

Pro tip: Snap a photo of the label on the side of the tank before you call. The serial number usually encodes the manufacture date, and the model number tells us the size and fuel type so we can bring the right parts or the right replacement.

If it’s time for a new one, a 40–50 gallon gas tank typically runs $1,200–$2,000 installed and electric runs $1,000–$1,800. Our water heater replacement cost guide breaks down tankless and hybrid options too.

Is this an emergency, or can it wait until morning?

It can usually wait if the water and fuel are off and the leak has stopped. Our standard hours are Monday through Saturday, 7 a.m. to 7 p.m.

Call now if you can’t get the water shut off, water is reaching finished space, or the relief valve keeps discharging hot water. If you smell gas, leave first and call 911 or the gas utility from outside. We answer (515) 494-5483 24/7. After-hours visits carry a $75–$125 dispatch premium on top of standard pricing, not tripled rates, and the diagnostic is free with any water heater repair. More on what we cover is on our water heater service page and emergency service page.