Water Heater Installation Guide
Complete guide for installing electric and gas water heaters, including tankless models. Learn proper sizing, venting, and safety requirements.
Estimated Time
4-6 hours
Tools Required
10 items
Materials Needed
9 items
Installing a water heater is one of the more significant plumbing projects a homeowner can tackle. Whether you're replacing an old unit or installing a new system, proper installation ensures safe operation, energy efficiency, and compliance with local codes.
Electric water heater installation is more accessible for DIY enthusiasts compared to gas models, which involve potentially dangerous gas line connections. Most electric tank replacements take 4-6 hours and can cut professional installation costs nearly in half.
This guide covers electric tank water heaters, the most common residential type. If you're considering a gas water heater or tankless model, professional installation is strongly recommended due to gas line work and significant electrical upgrades required.
Safety Precautions
- Turn off power at the circuit breaker and verify with a non-contact voltage tester before starting any electrical work
- Turn off the cold water supply to the existing water heater
- Allow hot water to cool completely before draining - run hot water faucets until water is cool to the touch
- Wear safety glasses and gloves when working with tools and moving the heavy water heater
- Never turn on electricity before the tank is completely full of water - this will instantly burn out the heating element
- Ensure adequate ventilation in the work area
- Have a helper available - water heaters are heavy and awkward to move
- Check local building codes for permit requirements before beginning
Tools Required
- Pipe wrench
- Adjustable wrench
- Screwdriver set
- Drill with bits
- Level
- Tape measure
- Garden hose
- Bucket
- Voltage tester (for electric)
- Pipe cutter or hacksaw
Materials Needed
- New water heater
- Flexible water supply lines
- Temperature and pressure relief valve
- Discharge pipe
- Pipe thread sealant
- Wire nuts (for electric)
- Gas-rated flexible connector (for gas)
- Drain pan
- Earthquake straps (where required)
Preparation
Check Permit Requirements
Contact your local building department to determine if a permit is required. Many jurisdictions require permits for water heater installations to ensure work meets current safety and plumbing codes. The permit process typically includes an inspection after installation.
Choose the Right Size
Select a water heater with appropriate capacity for your household. A 40-50 gallon tank typically serves 2-4 people, while larger families may need 60-80 gallons. Check the first-hour rating (FHR) to ensure it meets your peak demand.
Prepare the Installation Area
Clear the area around your existing water heater. Ensure the new unit will fit in the same location with at least 6 inches of clearance on all sides for ventilation. Place a drain pan underneath if required by local code or if the unit is located where leaks could cause damage.
Gather Materials
Purchase flexible water connectors (braided stainless steel lines make installation much easier), a new temperature and pressure relief valve, pipe thread sealant, a drain pan if needed, and an approved discharge pipe for the relief valve.
Installation Steps
Shut Off Utilities and Drain Old Water Heater
At your electrical panel, switch the water heater's circuit breaker to OFF. Use a non-contact voltage tester at the unit's electrical box to confirm power is completely off.
Shut off the cold water supply valve feeding the water heater. Connect a garden hose to the drain valve at the bottom of the tank and run it to a floor drain or outside. Open the drain valve and a hot water faucet somewhere in the house to allow air in and help the tank drain faster.
Draining a full 50-gallon tank takes 20-30 minutes. Once empty, disconnect the water supply lines and electrical connections.
Pro Tips:
- Place buckets or towels under connections to catch any residual water
- Take photos of electrical connections before disconnecting for reference during installation
Warning:
- Water will be hot if the heater was recently used - allow it to cool first
Remove Old Water Heater
After disconnecting all lines, carefully remove the old water heater. Water heaters are heavy even when empty - an empty 50-gallon tank weighs around 100-150 pounds. Use proper lifting techniques and get help if needed.
If the water heater is in a tight space, you may need to use a hand truck or appliance dolly. Clear a path to your disposal area.
Inspect the area where the old heater sat. Check for water damage, rust, or other issues that should be addressed before installing the new unit.
Pro Tips:
- Many retailers offer removal and disposal of your old water heater when delivering a new one
- Check with your local waste management for proper disposal options
Position New Water Heater
Place the new water heater in position, ensuring it sits level. Use shims if necessary to level the unit. The water heater should be positioned to leave at least 6 inches of clearance around it for ventilation and maintenance access.
If required by code in your area, place a drain pan underneath the water heater. The pan should be at least 2 inches deep and drain to an appropriate location.
In earthquake-prone regions, install seismic straps according to local code requirements. These straps prevent the water heater from tipping during an earthquake.
Warning:
- Never install a water heater directly on carpeting or near flammable materials
- Ensure the floor can support the weight of a full water heater (500+ pounds when full)
Install Temperature and Pressure Relief Valve
The T&P relief valve is a critical safety device that prevents dangerous pressure buildup. Even if your new water heater came with a valve installed, it's good practice to check it or install a new one.
Wrap the threads of the T&P valve with Teflon tape (3-4 wraps in the direction of installation). Thread the valve into the fitting on top or side of the tank and tighten firmly with a pipe wrench.
Attach the discharge pipe to the T&P valve. This pipe must run continuously downward and terminate 6 inches above the floor or drain pan. Never cap or plug this pipe.
Pro Tips:
- Use two wrenches - one to hold the tank fitting and one to tighten the valve
- The discharge pipe should be the same size as the valve outlet (typically 3/4 inch)
Connect Water Lines
Install flexible water connectors to both the hot and cold water connections on top of the tank. Flexible connectors (typically braided stainless steel) make installation much easier than rigid pipe because they don't require perfect alignment.
Hand-tighten the connectors first, then use a wrench to tighten an additional quarter to half turn. Don't overtighten - this can damage the fittings.
The cold water line connects to the inlet (usually marked or on the right side), and the hot water line connects to the outlet. Some codes require a shut-off valve on the cold water line if one isn't already present.
Warning:
- Ensure you connect hot to hot and cold to cold - reversed connections will cause problems
- Check that all fittings have washers installed
Make Electrical Connections
Remove the electrical access cover on the water heater. You'll see the unit's wiring with wire leads (typically two hot wires and a ground).
Feed the electrical cable from your circuit breaker through the cable connector on the water heater. Connect the wires using wire nuts: black wire to black wire, white wire to white wire (and mark the white wire with black tape since it carries power), and ground wire to the green ground screw.
Replace the electrical access cover. Ensure all connections are tight and no bare wire is exposed outside the wire nuts.
Warning:
- Confirm power is OFF at the breaker before making any electrical connections
- Use wire nuts rated for the wire size you're connecting
- If you're not comfortable with electrical work, hire an electrician for this step
Fill Tank and Check for Leaks
Open the cold water supply valve to begin filling the tank. Go to a hot water faucet in the house and open it fully. You'll hear air sputtering out as the tank fills - this is normal.
Let the faucet run until you get a strong, steady stream of water with no air bubbles. This confirms the tank is completely full. This process takes 10-15 minutes for most tanks.
While the tank is filling, check all water connections for leaks. Tighten any connections that show signs of dripping.
Pro Tips:
- Watch the drain pan and floor around the water heater for any signs of leakage
- Small weeping at compression fittings often stops once the fitting is fully pressurized
Warning:
- DO NOT turn on electrical power until you've confirmed the tank is completely full of water
Turn On Power and Set Temperature
Only after confirming the tank is completely full (steady water flow from a hot water tap with no air), turn the circuit breaker back on.
Set the thermostat to your desired temperature. 120°F is recommended for most households as it prevents scalding and saves energy. The thermostat is typically located behind an access panel.
It takes 60-90 minutes for the water heater to heat a full tank of cold water. After this time, test the hot water at a faucet.
Pro Tips:
- Mark your calendar to flush the tank every 6-12 months to remove sediment
- Test the T&P relief valve annually by lifting the lever slightly
Common Mistakes to Avoid
- Turning on electricity before the tank is full - This instantly burns out the upper heating element and requires replacement
- Overtightening water connections - This can crack fittings and cause leaks
- Not installing a new T&P valve or discharge pipe - The T&P valve is critical for safety
- Incorrect electrical connections - Always match wire colors and use proper wire nuts
- Installing without proper clearance - Inadequate space prevents proper ventilation and maintenance access
- Forgetting to check for leaks before finishing - Small leaks can become major problems
- Not getting required permits - This can affect home insurance and resale value
Tips and Tricks
- Buy flexible water supply lines instead of soldering copper - They're much easier to install and allow for minor misalignments
- Take photos of all connections on your old water heater before removing it
- Install a drain pan even if not required by code - It provides protection against leaks
- Consider adding a water heater timer to reduce energy costs if you have time-of-use electrical rates
- Install an expansion tank if required by code or if you have a closed plumbing system
- Label the circuit breaker clearly for future reference
- Keep the receipt and warranty information in a safe place
When to Call a Professional
Consider hiring a professional plumber if:
- You're installing a gas water heater - Gas line connections require special licensing and expertise
- You're installing a tankless water heater - These often require significant electrical upgrades and special venting
- Your installation requires new plumbing or electrical lines
- You're not comfortable working with electricity
- Local codes require licensed plumber installation
- You need to relocate the water heater to a different area
- You encounter unexpected problems like corroded pipes or insufficient electrical service
Code Considerations
Water heater installation is governed by multiple codes including plumbing, electrical, and building codes. Requirements vary by location but commonly include:
- Permits: Most jurisdictions require a permit for water heater replacement. Permit costs typically range from $50-150.
- T&P Relief Valve: Required on all tank water heaters with proper discharge piping terminating 6 inches from the floor.
- Drain Pan: Required in areas where leakage could cause damage (attics, upper floors, above living spaces).
- Seismic Straps: Required in earthquake-prone areas to secure the water heater against tipping.
- Clearances: Minimum clearances from combustible materials must be maintained.
- Electrical: Circuit must be dedicated to the water heater with proper wire gauge (typically 10/2 for most residential units).
- Expansion Tank: Required in closed plumbing systems where a backflow preventer is installed.
Always check with your local building department for specific requirements in your area.
Maintenance Tips
Regular Maintenance Schedule
- Monthly: Check for leaks around the tank and connections
- Every 6 months: Test the T&P relief valve by lifting the lever slightly - water should flow and stop when released
- Annually: Flush 2-3 gallons of water from the drain valve to remove sediment buildup
- Every 3-5 years: Consider flushing the entire tank or hiring a plumber for complete maintenance
Signs Your Water Heater Needs Attention
- Rusty or discolored water
- Strange noises (popping, rumbling) indicating sediment buildup
- Leaks around the base or connections
- Inconsistent water temperature
- Age over 10-12 years (consider replacement)
Cost Estimate
DIY Installation Costs
- 40-50 gallon electric water heater: $400-800
- Flexible water supply lines: $20-40
- T&P relief valve and discharge pipe: $15-30
- Drain pan (if needed): $20-40
- Pipe thread sealant, wire nuts, misc supplies: $20-30
- Permit: $50-150
- Total DIY Cost: $525-1,090
Professional Installation Costs
- Professional electric water heater installation: $1,200-2,000
- Gas water heater installation: $1,500-2,500
- Tankless water heater installation: $2,500-4,500
Potential Savings: DIY electric water heater installation can save $600-900 compared to professional installation, though gas and tankless models should always be professionally installed.
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