How to Replace a Water Heater Expansion Tank
About This Project
This guide provides comprehensive, step-by-step instructions for safely replacing a failed or old water heater expansion tank. The process involves shutting off power and water to the heater, draining the system to a safe level, removing the old tank, preparing and installing the new tank, and then carefully restoring the system to full operation while checking for leaks.
Best for experienced DIYers and homeowners with some experience with basic plumbing knowledge and familiarity with power tools. Requires Klein Tools Voltage/Continuity Tester ET250.
Tools & Materials
Bucket
WYPALL L40 Towels, Dry Up Towels, 19-1/2 in. x 42 in., White, 200 Towels/Roll KCC05860
Klein Tools Voltage/Continuity Tester ET250
GardenJoy PVC Garden Hose 5/8 in. x 75 ft. Heavy-Duty Durable Hose Outdoor Water Hose LG-GHB5875
Screwdriver
Husky 12 in. PVC Pliers 17PL0309
Bucket
Ideal for carrying or storing liquids.
WYPALL L40 Towels, Dry Up Towels, 19-1/2 in. x 42 in., White, 200 Towels/Roll KCC05860
WYPALL L40 Wipers are effective wipers that absorb liquids lightning-fast. These wipes are made of bonded cellulose using DRC (double re-creped) technology for strength, softness and absorbency. As a wiping cloth, it soaks up liquids fast, but all you'll feel is softness, thanks to a plush, touchable outer layer. In fact, it's a popular choice for patient wiping in healthcare industries, for bathing and patient drying. These utility wipes are specially designed to absorb liquids, lubricants and oils (in restaurants for wiping counters, in mechanic shops, industrial and commercial factories and more), yet they're soft enough for use on face and hands. Experience the difference in superior absorbency and cleaning at your home or office today. Towel/Wipe Type: Dry Wipes; Application: Bathrooms; Material(s): Cloth-Like; Number of Plies: 1.
Klein Tools Voltage/Continuity Tester ET250
Klein Tools ET250 is a solid-state, digital voltage and continuity tester. It measures AC/DC voltages up to 600V and tests for continuity. Additionally, the ET250 tests GFCI protected circuits to verify
GardenJoy PVC Garden Hose 5/8 in. x 75 ft. Heavy-Duty Durable Hose Outdoor Water Hose LG-GHB5875
Light-weight and Flexible: Made from premium PVC, our garden hose is both light-weight and durable, allowing for easy handling without kinks or tangles, ideal for all your watering and cleaning needs.
Screwdriver
A tool used to turn screws.
Husky 12 in. PVC Pliers 17PL0309
Husky's 12 in. PVC Pliers work in tight spaces with optimal compression. They are ideal for unfastening or tightening large diameter PVC pipe, conduit and fittings. 3 sets of right-angle teeth provide
Steps
Preparation and Safety Precautions
15 minsBegin by ensuring the work area is safe. Go to your home's main electrical panel and turn off the circuit breaker that supplies power to the electric water heater. For added safety, use a voltage tester at the heater's electrical connection to confirm the power is off. Next, locate the cold water inlet valve for the water heater and turn it clockwise to shut off the water supply. Finally, place a bucket and some old towels on the floor beneath the expansion tank to catch any water that will inevitably spill during the process.
Drain the System Pressure and Water Level
20 minsTo relieve pressure in the system, go to a sink nearby (preferably on a lower floor) and open the hot water tap fully. Leave it open. Next, connect a standard garden hose to the drain valve located at the bottom of the water heater tank. Place the other end of the hose in a floor drain or run it outside. Open the drain valve by turning the handle or using a screwdriver. You only need to drain a few gallons of water, just enough to ensure the water level is below the height of the expansion tank connection. Once drained sufficiently, close the drain valve.
Prepare the New Expansion Tank
10 minsUnbox your new expansion tank. Using a standard tire pressure gauge, check the air pressure via the Schrader valve (air stem) located on top of the tank. This pressure must match your home's water pressure. The ideal pressure is often listed on your home's pressure reducing valve (PRV), typically between 50-60 PSI. If the tank's pressure is too low or high, use a bicycle pump or small air compressor to add or release air until it matches. Next, take your roll of Teflon tape and wrap it clockwise around the male threads of the new tank 3 to 4 times. This will ensure a watertight seal.
Remove the Old Expansion Tank
15 minsPosition your bucket directly under the old tank. Take your first pipe wrench and securely grip the metal fitting at the base of the expansion tank. Use a second pipe wrench to grip the pipe tee that the tank is threaded into; this is your 'hold-back' wrench. By holding the pipe tee stationary, you prevent the entire plumbing assembly from twisting or breaking. Apply force to the first wrench in a counter-clockwise direction to unscrew the tank. Be prepared for the tank's weight; a failed tank is often full of water and surprisingly heavy. Carefully support it as you finish unthreading it by hand and lift it down.
Install the New Expansion Tank
15 minsUse a clean rag to wipe the female threads on the pipe tee, removing any old Teflon tape or debris. Carefully lift the new expansion tank into place. To prevent cross-threading, start screwing the tank into the fitting by hand. You should be able to get several rotations before it becomes snug. Once it is hand-tight, place one pipe wrench on the fitting at the base of the new tank and your second 'hold-back' wrench on the pipe tee. Tighten the tank clockwise an additional one to two full turns. The connection should feel very snug, but do not overtighten, as this can crack the fittings.
Restore Water and Check for Leaks
15 minsEnsure the water heater's drain valve is fully closed and disconnect your garden hose. Go to the cold water inlet valve and turn it on SLOWLY. This prevents a 'water hammer' effect that could damage your pipes. You will hear water filling the tank. Let the hot water faucet that you opened earlier continue to run; you will hear it sputter as air is pushed out of the lines. Once water flows from the faucet in a steady, air-free stream, you can turn it off. Now, meticulously inspect the new connection where the expansion tank is installed. Use a dry paper towel to wipe around the joint; it will make even the smallest bead of moisture obvious. If you find any leaks, you must shut off the water, drain the system again, and re-seal the connection.
Restore Power and Final Cleanup
10 minsOnce you have double-checked that there are absolutely no leaks and the water heater tank is full (indicated by a steady flow from the hot water taps), you can safely restore power. Go back to the electrical panel and flip the water heater's circuit breaker back to the 'ON' position. The water heater will now begin to heat the water in the tank. Tidy up your tools, wipe up any spilled water, and dispose of the old expansion tank according to your local recycling or waste disposal regulations, as it is considered scrap metal.
Common Problems
Failing to shut off utilities can lead to serious injury or property damage. By shutting off the isolation valves first, you keep the tank isolated from the rest of the potable water system.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Ensure the gas and water are completely shut off before starting disassembly. Water heaters are heavy; get help if needed.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Failure to turn off the power at the circuit breaker can result in serious electrical shock.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Failure to turn off power to the unit before working on it can result in serious injury or death.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Risk of scalding or injury if the water heater is left on.
Solution: Some manufacturers may suggest leaving the unit on, but turning it off is the universally safer method.
Failure to shut off the gas supply can lead to a dangerous gas leak.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
This is the most important safety step. Failure to turn off the electricity can result in severe electrical shock.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Frequently Asked Questions
How difficult is this project for a beginner, and how long should I expect it to take?
This project is considered beginner-friendly, but requires careful attention to safety and step-by-step instructions. Most DIYers can complete it within 1-2 hours, assuming all tools and materials are gathered beforehand. The primary cost will be the new expansion tank itself, typically ranging from $40 to $100.
What are the most important safety precautions I need to take before starting this project?
The most critical safety steps are shutting off both the power (electric or gas) and the main water supply to your water heater. Always ensure the system is completely depressurized and drained to a safe level before attempting to remove the old tank. Have plenty of towels and a bucket ready for any residual water.
Do I really need all the listed tools, particularly the air compressor and pipe wrench?
Yes, most of the listed tools are essential for a safe and successful replacement. A pipe wrench is crucial for loosening potentially stubborn pipe connections, while the tire pressure gauge is vital for accurately pre-charging the new expansion tank to match your home's water pressure, which prevents premature failure. An air compressor can make this pre-charging easier if you have one, but a hand pump can also work.
What's the most common mistake DIYers make when installing a new expansion tank, and how can I avoid it?
The most frequent mistake is neglecting to properly pre-charge the new expansion tank with air before installation. Use a tire pressure gauge to set the tank's air pressure to match your home's incoming cold water pressure (usually between 40-70 PSI) to ensure it functions correctly. Failing to do this can lead to the tank becoming waterlogged and failing prematurely.
How can I tell if my existing water heater expansion tank needs to be replaced?
Common indicators of a failing expansion tank include water dripping from your water heater's temperature and pressure relief valve, fluctuating water pressure at fixtures, or banging noises in your pipes. You can also tap on the tank; if it sounds full of water (a dull thud) rather than hollow (a ringing sound), it's likely waterlogged and needs replacement.
Is Teflon tape absolutely necessary, and are there different types of expansion tanks I should consider?
Yes, Teflon tape (or pipe thread sealant) is highly recommended for all threaded connections to ensure a watertight seal and prevent leaks. While the Amtrol No 60 is a common residential choice, expansion tanks come in various sizes (e.g., EX-30, EX-90) depending on your water heater's capacity and system pressure. Always choose a tank rated appropriately for your specific water heater and home's water pressure.
