Water heater replacement: what a pro does and what you can do
Gas or electric, both need a licensed pro and a permit in most cities. Your job is to know what you have, hire well, and check the code items when it is done.
Difficulty 4 of 5 · licensed pro
Stop here
Photo of your room, the look you pick, then this guide with the materials counted for your room.
What you need
- Carbon monoxide alarm
- Drain pan for the new tank
- Job folder for the bid, permit, and manual
- Storage bins to clear the space around the heater
Tools
- Phone camera to photograph the data plate and the installation
- Tape measure for the space, the door, and the path
- Bright flashlight
- Cooking thermometer to check the hot water temperature at a faucet
- Notebook for comparing bids
Step by step
Step 1 of 12
Accept the boundary: this is licensed work
Gas piping, venting, combustion air, and seismic bracing are not homeowner tasks in California, and in Los Angeles the replacement is permitted and inspected. Your part is knowing what you have, hiring a licensed plumber, preparing the space, and checking the visible code items at the end. Read the stop-gate before you go on.
Before you go further
- You will not touch the gas line, the vent, or the relief valve
- You understand this needs a licensed plumber and a permit
- You know where the gas shutoff and the cold water shutoff are
- There is a working carbon monoxide alarm in the house
- If you ever smell gas, you leave first and call from outside
Step 2 of 12
Photograph the data plate and measure the space
Photograph the label on the side of the tank so the capacity, the fuel, the input rating, the model, and the manufacture date are all readable. Then measure the height and width of the space, the door and hallway the new tank has to come through, and the clearance around it. Send these photos with every request for a bid.
Step 3 of 12
Write down how the current one fails you
Note the age from the data plate, whether you run out of hot water, any rust at the base, moisture in the pan, rumbling from sediment, or a pilot that will not stay lit. A tank leaking from the bottom is failing now and needs a same-week call, not a comparison shopping week. Put the notes with the photos.
Step 4 of 12
Decide what kind of replacement you want
Like-for-like is the simplest and cheapest: the same fuel, roughly the same capacity, same location. A heat pump water heater uses much less energy but needs a 240 V circuit, enough air volume around it, and a condensate drain; a tankless unit needs a larger gas line and a different vent. Ask each bidder what your house would actually need for each option, and check for current utility rebates before you decide.
Step 5 of 12
Learn the code items the inspector will look at
Know these five before anyone quotes: seismic strapping, the temperature and pressure relief valve and its discharge piping, the vent and combustion air on a gas unit, a drain pan where a leak would do damage, and an expansion tank where the house has a pressure regulator or a check valve on the water service. You are not installing any of them — you are going to look for them at the end. Ask your plumber to confirm which apply to your house.
Step 6 of 12
Check the license and get three bids
Look up each contractor on the California licensing board website and confirm an active plumbing license in the name of the business bidding, plus workers' compensation if they have employees. Send all three the same photos and measurements. Ask each one what they would do differently and why — the answers tell you who actually looked.
Step 7 of 12
Make the bid name the permit and the parts
The written bid should name the model being installed and its warranty, the permit and who pulls it, haul-away of the old tank, new water connectors, a new gas flex connector and shutoff on a gas unit, seismic straps, the relief valve discharge line, a pan and an expansion tank if required, and the labor. Ask specifically whether the vent connector is being replaced. A bid with no permit line is not a cheaper bid, it is a different job.
Step 8 of 12
Clear the space and the path
Empty the closet or the garage corner completely, including anything stored against the tank, and clear a straight path from the door to the heater wide enough to roll a tank on a dolly. Move paint, solvents, and cardboard away from a gas appliance permanently, not just for the day. Protect the floor along the path if it is finished.
Step 9 of 12
Know what happens to the house that day
Expect no hot water for most of a day and the cold water off for part of it, so fill a couple of pitchers and run the dishwasher the night before. Plan to be home, keep pets and kids out of the work area, and keep the path clear. Photograph the old installation from three angles right before they start.
Step 10 of 12
Look at the strapping and the setting
When the new tank is in, look for two straps — one around the upper third and one around the lower third of the tank — anchored into framing or masonry, not just into drywall. The tank should sit level and solid on its stand or in its pan, and in a garage the installer should confirm whether your unit still has to be elevated or is listed as flammable-vapor-ignition-resistant. Photograph what you see.
Step 11 of 12
Follow the relief line and watch the draft test
Trace the pipe leaving the relief valve on top or on the side of the tank: it should run downhill, stay full size the whole way, and end at an approved point of discharge where a discharge would be seen — never capped or plugged. On a gas unit, ask the plumber to perform a draft test at the draft hood with the burner running and the house closed up, and to show you the result. Ask them to leak-test the gas connections in front of you.
Step 12 of 12
Close the job: temperature, inspection, paperwork
Ask for the thermostat to be set to 120°F, then check a faucet with a thermometer after an hour and note the reading. Hold the final payment until the city inspection is signed off, register the warranty, write the install date on the tank with a marker, and file the permit, manual, and invoice together. Look under the tank once a day for the first week.
Quality check
- Plumbing license and insurance verified before signing
- Permit pulled by the plumber and final inspection signed off
- Two seismic straps, upper and lower third, anchored into framing
- Relief valve discharge line full size, running downhill, not capped
- Gas connections leak-tested and a draft test performed in front of you
- Pan and expansion tank installed if the plumber said they were required
- Thermostat set to 120°F and verified at a faucet
- Working carbon monoxide alarm in the house
- No leaks under or around the tank after the first week
Common mistakes
- Treating it as a Saturday swap. The videos make it look like two unions and a flex line. What they leave out is the gas connection, the combustion air, the vent connector, the draft test, the seismic straps, the relief piping, and the permit. Any one of those done wrong can fill the house with carbon monoxide or flood it. Mistake #1 in this task: this is licensed work, hire it.
- Letting the plumber skip the permit. An unpermitted water heater shows up at resale, can void an insurance claim after a leak or a fire, and removes the one independent check that the venting and strapping are right. The permit costs little and the plumber should pull it in their own name.
- Buying by price instead of by what fits. Height, diameter, the door opening, the clearance around the tank, the vent size, and the gas line capacity all constrain the replacement. Measure and photograph the data plate before anyone quotes, and make each bid name a specific model number.
- Accepting one strap, or no strap. California requires a water heater to be braced against earthquakes, and the standard practice is two straps — one around the upper third and one around the lower third of the tank, anchored into framing. A single strap around the middle is not it. Look at it yourself when the job is done.
- A relief valve piped wrong, or capped. The temperature and pressure relief valve is the thing that keeps the tank from becoming a bomb. Its discharge line must be full size, run downhill, and terminate at an approved point where a discharge is visible — never capped, never reduced, never threaded closed. If you see a plug on it, that is an emergency.
Draft guide written from standard practice, not yet reviewed by a licensed pro. Follow product labels where they differ.
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