A broken water heater means cold showers, no hot dishes, and a clock ticking fast. Knowing how to install a water heater can save you time and money, whether you go DIY or hire a pro. This guide walks you through every step from shutting off the gas or power to lighting the pilot light for both electric and gas tank models.
Read this before you pick up a wrench. It covers what tools you need, what mistakes to avoid, how long the job takes, and when to call a licensed plumber.
Understanding Water Heater Installation
Water heater installation means connecting a new unit to your home’s water supply, energy source (gas or electric), and for gas models a venting system. It sounds complex, but broken into clear steps, it is very manageable.
There are three common types:
- Tank water heaters — Store 40 to 80 gallons. Most homes have these. Easiest to install.
- Tankless water heaters — Heat water on demand. More efficient but harder to install.
- Heat pump water heaters — Move heat from surrounding air into the tank. Very efficient. Need at least 450 cubic feet of air space around them.
This guide focuses on standard tank-style hot water heater installation, covering both gas and electric models. It also includes a comparison table so you can see which type fits your home best.
| Type | Avg. Cost (Unit) | Install Time | Best For |
| Electric Tank | $400–$900 | 2–4 hours | Smaller homes, no gas line |
| Gas Tank | $500–$1,200 | 3–5 hours | Larger families, lower monthly bills |
| Tankless | $700–$2,000 | 4–8 hours | High efficiency, limited space |
| Heat Pump | $1,000–$2,000 | 4–6 hours | Energy savings, warm climates |
California homeowners: Check with your local building department before starting. Los Angeles and surrounding areas follow California Title 24 energy codes. The LADBS (Los Angeles Department of Building and Safety) requires a permit for most water heater replacements. Skipping a permit can cause problems when you sell your home or file an insurance claim.
What You’ll Need Before You Start
Getting your tools and parts ready before the water heater install saves a lot of headaches. Here is a complete list:
Tools:
- Pipe wrench and adjustable wrench
- Voltage tester (for electric heaters)
- Tubing cutter
- Hand truck or appliance dolly
- Soapy water in a spray bottle (gas leak check)
- Bucket and garden hose
- Level
Parts and Materials:
- New T&P (temperature and pressure) relief valve always buy new, never reuse
- Teflon plumber’s tape
- Flexible water connectors (3/4-inch)
- Flexible gas connector (gas models only)
- Discharge pipe for the T&P valve
- Metal drain pan (at least 2 inches wider than the unit)
- Expansion tank (if you have a closed plumbing system)
- Pipe dope or joint compound
Pro tip: Buy a new T&P relief valve even if the old one looks fine. They are cheap, usually $10 to $20 and a faulty one is a serious safety risk.
Before You Start: Check These First
Get a permit. Most cities require a plumbing permit for water heater replacement. Call your local building department before starting. Skipping this can create problems when you sell your home or file an insurance claim.
Check water pressure. Use a pressure gauge on your outdoor spigot. Ideal pressure is 50 to 60 PSI. Anything over 80 PSI needs a pressure-reducing valve before you install the new unit.
Do you need an expansion tank? If your home has a closed plumbing system, pressure spikes have nowhere to go. A 2-gallon expansion tank works with units up to 50 gallons. A 5-gallon tank covers up to 100 gallons. Match the tank’s air pressure to your home’s water pressure.
Repair or replace? If you are not getting hot water, the heating element may have failed. Water pooling under the tank usually means a full replacement is needed. Check the data plate on your current unit for the manufacture date, size, and specs before buying a new one.
Step-by-Step: How to Install a Water Heater
Removing the Old Unit
These steps apply to both gas and electric water heater installation.
Step 1: Shut off the power or gas
- Electric: Flip the circuit breaker to OFF. Use a voltage tester to confirm power is off.
- Gas: Turn the gas control valve to “Pilot.” Then close the main gas supply valve.
Step 2: Let the water cool Open a hot water faucet and let it run for 10 minutes. This prevents scalding when you drain the tank.
Step 3: Shut off the cold water supply Turn the cold water supply valve at the top of the old tank to OFF.
Step 4: Drain the tank Connect a garden hose to the drain valve at the bottom of the tank. Run the other end to a floor drain or outside. Open the drain valve. Turn on a hot water tap inside to speed drainage. This takes 30 to 60 minutes.
Step 5: Disconnect the water and energy lines
- Electric: Disconnect the wire connections in the junction box. Remove the ground wire from the green screw. Cap your home’s power wires with wire nuts.
- Gas: Break the union between gas lines using two wrenches. Cap the gas line. Remove the gas pipe from the control valve.
Step 6: Disconnect the vent pipe (gas models) Let the exhaust vent pipe cool completely before touching it. Remove it from the draft hood carefully. Prop or tie it up if needed — you will reuse or replace it.
Step 7: Remove the T&P valve and discharge pipe Disconnect the old T&P relief valve and its discharge pipe. You can reuse the discharge pipe if it is in good shape. Never reuse the T&P valve itself.
Step 8: Disconnect water lines and remove the old unit Use a wrench to detach both water lines. Water heaters are heavy, typically 100 to 150 pounds empty. Use a hand truck and ask someone for help.
Installing the New Electric Water Heater
Step 1: Position and level the unit Place the new heater in a metal drain pan in the same spot as the old one. Use a level to make sure it sits flat.
Step 2: Install the T&P relief valve Wrap Teflon tape around the threads. Screw the new T&P valve into the designated port. Attach the discharge pipe it must point downward and end within 6 inches of the floor.
Step 3: Connect the water lines
- Wrap Teflon tape around the cold and hot water port threads.
- Connect the cold water supply line to the “cold in” port (usually marked blue).
- Connect the hot water outlet to the “hot out” port (usually marked red).
- Hand-tighten first, then snug with a wrench. Do not overtighten.
- If you have a closed plumbing system, install a properly sized expansion tank on the cold water line now.
Step 4: Fill the tank Open the cold water supply valve. Open 2 to 3 hot water taps in your home. Let water run until you get a steady flow with no air bubbles. This means the tank is full. Never power on an empty electric water heater it will destroy the heating elements.
Step 5: Make the electrical connections Remove the access panel on the heater to expose the junction box. Connect the power wires to the heater’s terminals, matching wire colors to your installation manual. Attach the ground wire to the green ground screw. Replace the access panel.
Step 6: Power on and set the thermostat Flip the circuit breaker back on. Set the thermostat to 120°F. This is the sweet spot for energy savings and safety. You can raise it to 130°F if needed. The first tank takes 1 to 2 hours to fully heat.
Installing the New Gas Water Heater
Step 1: Install the drain pan and position the unit Set the metal drain pan in place first. Place the new gas water heater inside it. Level the unit using the adjustable feet on the bottom.
Step 2: Install heat trap fittings and connect water lines Install the heat trap fittings on the hot and cold ports. Connect water lines using 3/4-inch NPT threaded adapters. Wrap all threaded connections with Teflon tape. Add an expansion tank on the cold line if you have a closed plumbing system.
Step 3: Install the T&P valve and discharge pipe Install the new T&P relief valve. Attach the discharge pipe — 3/4-inch interior diameter, sloping downward, ending within 1 to 6 inches of a drain.
Step 4: Connect the gas supply line Connect the flexible gas connector to the gas inlet on the unit and to your home’s gas supply line. Use two wrenches to avoid straining the fittings. Do not use the old flexible connector — always use a new one.
Step 5: Reconnect the vent pipe Reattach the exhaust vent pipe to the draft hood at the top of the unit. Make sure it slopes upward toward the vent outlet and has no dips or low points. Gas needs to vent straight out — any sags trap carbon monoxide.
Step 6: Fill the tank and check for water leaks Turn on the cold water supply valve. Open a hot water tap in the house. Let water run for 3 minutes to purge air from the tank. Check all water connections carefully for drips.
Step 7: Turn on the gas and check for gas leaks. Open the gas valve slowly. Spray all gas connections with soapy water. Bubbles mean a leak closes the gas valve immediately and tightens the fitting. Do not proceed until there are zero bubbles.
Step 8: Ignite the pilot light Turn the gas control valve to “Pilot.” Press the control knob down and hold it while using the igniter. Hold for 30 seconds after the pilot lights. Slowly turn to your desired temperature setting. The status light will start blinking.
You can read about: How to Install Tankless Water Heater
How Long Does Water Heater Installation Take?
| Task | Time Estimate |
| Draining the old tank | 30–60 minutes |
| Removing the old unit | 30–45 minutes |
| Installing the new unit (electric) | 1–2 hours |
| Installing the new unit (gas) | 2–3 hours |
| First heat-up (electric) | 1–2 hours |
| Total (DIY, electric) | 3–5 hours |
| Total (DIY, gas) | 4–6 hours |
A licensed plumber can usually complete the full job in 2 to 3 hours because they come prepared with all tools and materials.
Common Water Heater Installation Mistakes
Rushing or skipping steps causes most problems. Watch out for these:
- Reusing the T&P relief valve The old valve may look fine but could be corroded inside. A failed T&P valve can cause dangerous pressure buildup. Always replace it.
- Not checking for gas leaks This is non-negotiable. Every gas fitting must be tested with soapy water before you light the pilot. Bubbles mean danger.
- Powering on an empty electric heater The heating elements will burn out in minutes if the tank is dry. Always fill completely before turning on the breaker.
- Wrong vent slope on gas heaters The exhaust vent must slope upward continuously. Any dip or low point traps carbon monoxide inside your home.
- Skipping the permit In most California cities, a permit is required for water heater replacement. Skipping it can void your homeowner’s insurance and create legal issues when you sell.
- Overtightening fittings Use firm hand pressure, then one quarter-turn with a wrench. Overtightening cracks fittings and causes leaks.
- Ignoring sediment in the old tank If your old tank had heavy sediment buildup, flush your new one every 6 to 12 months to keep it running efficiently.
Water Heater Sizing Guide: What Size Do You Need?
Getting the right size matters. Too small and you run out of hot water. Too large and you waste energy heating water you never use.
For tank water heaters:
| Household Size | Recommended Tank Size |
| 1–2 people | 30–40 gallons |
| 3–4 people | 40–50 gallons |
| 5+ people | 50–80 gallons |
For tankless water heaters, sizing is based on gallons per minute (GPM) and temperature rise not tank size. A family of four in Southern California typically needs a unit rated for 5 to 6 GPM.
For heat pump models, you need at least 450 cubic feet of surrounding air space and a location that stays between 40°F and 90°F year-round; a basement or garage works well.
Also check your home’s energy source. If you currently have an electric heater and want to switch to gas, you will need a licensed gas fitter to run a new gas line. That adds cost and time to the project.
DIY vs Professional Water Heater Installation
| Factor | DIY | Professional |
| Cost | $300–$700 (parts only) | $800–$1,800 (parts + labor) |
| Time | 4–6 hours | 2–3 hours |
| Safety risk | Higher if inexperienced | Low |
| Permits | Your responsibility | Often handled by plumber |
| Gas line work | Not recommended | Required |
| Warranty | May be voided | Usually protected |
When to hire a licensed plumber:
- You need to run a new gas line or upgrade its size
- You are switching fuel types (electric to gas or vice versa)
- Your electrical panel needs upgrading
- The job requires new venting
- You are not confident working with gas or high-voltage wiring
Gas leaks and electrical mistakes can be fatal. There is no shame in calling a pro for water heater install work that goes beyond a straight swap.
Water Heater Maintenance After Installation
A new water heater lasts 8 to 12 years for tank models and up to 20 years for tankless units but only if you maintain it.
Annual tasks:
- Test the T&P relief valve. Lift the lever briefly. Water should flow out and stop when you release it.
- Flush the tank to remove sediment. Connect a hose to the drain valve and let it run until the water runs clear.
- Check the anode rod. This is a magnesium or aluminum rod inside the tank that protects it from corrosion. Replace it every 3 to 5 years.
For tankless units:
- Flush with white vinegar once a year using an isolation valve kit.
- Check for error codes on the control panel regularly.
- Inspect the venting for blockages before winter.
For heat pump models:
- Clean the air filter every few months.
- Check the condensate drain line for clogs.
- Keep the area around the unit clear for proper airflow.
Why Choose Derks Plumbing?
If you are in the Eagle Rock area and want the job done right, Derks Plumbing is your local expert for Water Heater Installation in Eagle Rock. Our licensed plumbers handle everything from pulling permits and connecting gas lines to final inspections and cleanup.
We know California’s Title 24 codes and Los Angeles building requirements inside and out. We work with all major brands and all types of units: tank, tankless, electric, gas, and heat pump.
Whether it is a straight swap or a full conversion, we show up on time, do the job cleanly, and make sure your hot water is running before we leave. Contact us or fill out our online form to schedule your water heater install today.
Final Thoughts
Replacing a water heater is one of the more manageable home projects if you take it step by step and do not rush. The most important rules: never power on an empty electric heater, always test gas connections with soapy water, always replace the T&P valve, and always pull a permit if your city requires it.
If any part of the process involves gas line work, new venting, or electrical upgrades, call a licensed plumber. The cost of professional installation is far less than the cost of fixing a dangerous mistake.
Frequently Asked Questions (FAQs)
How long does it take to install a water heater?
A DIY electric water heater installation takes 3 to 5 hours. Gas takes 4 to 6 hours. A professional plumber typically finishes in 2 to 3 hours.
Do I need a permit for water heater installation?
In most California cities, yes. The LADBS requires permits for water heater replacement in the Los Angeles area. Check with your local building department before you start.
How much does water heater installation cost?
Parts and labor together typically run $800 to $1,800 for a standard tank unit. Electric units cost less than gas. Tankless and heat pump models cost more.
Can I install a water heater myself?
Yes, for a straight electric tank swap if you are comfortable with basic plumbing. Gas line work and new venting should always be handled by a licensed plumber.
What size water heater do I need?
For 1 to 2 people, a 30 to 40-gallon tank works. For 3 to 4 people, go with 40 to 50 gallons. For 5 or more, get a 50 to 80-gallon unit.
How often should I flush my water heater?
Once a year. Flushing removes sediment that builds up at the bottom of the tank and reduces efficiency.
