Keep Your Plumbing Efficient and Safe: Learn How to Replace a Water Heater Expansion Tank
If you have a water heater, you may already know about the importance of having an expansion tank installed. However, over time, it may start to malfunction or fail altogether, requiring a replacement.
While it may seem hard, replacing a water heater expansion tank is a relatively straightforward process that can be done with basic plumbing tools.
In this guide, we’ll walk you through the steps to replace your expansion tank, provide essential tips, and help you keep your plumbing in top shape.
Factors to Consider When Buying and Replacing a Water Heater Expansion Tank
What Is an Expansion Tank?
An expansion tank is a safety device that is installed in closed-loop water heating systems to help regulate the pressure and prevent damage to the plumbing system.
When water is heated, it expands and causes pressure to build up in the system. If you don’t replace a water heater expansion tank, the increased pressure from heated water can cause damage to pipes, valves, and other components, leading to leaks or even a ruptured water heater.
By installing a new tank, the excess water pressure is absorbed, reducing the risk of damage and prolonging the lifespan of the water heating system.
Additionally, it can help improve the efficiency of the system and lower energy costs. In short, this element is an important safety device that can save you money in the long run by preventing costly repairs and replacements.
How Does an Expansion Tank Work?
An expansion tank works by providing a space for the water to expand into as it heats up. The tank is typically installed near the water heater and is connected to the plumbing system with a T-shaped pipe. The top portion of the T-pipe connects to the water heater, while the bottom portion connects to the cold water supply line.
When the water in the water heater heats up, it expands and increases the pressure in the plumbing system. The excess water is then pushed into the expansion tank, which has a flexible membrane inside that expands to accommodate the increased volume of water. This process helps regulate the pressure in the system and prevents damage to the plumbing, such as leaks or burst pipes.
As the water cools down, the pressure in the system decreases, and the membrane in the tank contracts back to its original size. This allows the water to flow back into the system, ready to be heated again the next time it’s needed. By providing a safe and effective way to regulate pressure, an expansion tank helps protect your water heater and plumbing system, keeping your home safe and comfortable.
Expansion Tank Types
If you need to replace a water heater expansion tank, there are three types to choose from:
- Compression type
- Bladder type
- Diaphragm (bag) type
The compression type, also known as plain steel, is the oldest type, and it does not include the bladder. This is just an empty tank with the air cushion above the water, which must be controlled for the proper operation.
The bladder type uses the bladder that keeps the water separated from the precharged air cushion. As the water volume increases in the storage tank, it is directed into the expansion tank, and as it contracts, the fluid goes back into the heating system. The disadvantage of the bladder type is the potential corrosion of the tank, especially when exposed to potable water.
The diaphragm-type is designed as the container, divided into two sections, separated by a non-replaceable rubber diaphragm, which looks like a bag. The system water is contained inside the diaphragm and connected to the plumbing system, while the other side includes air under pressure. The advantage here is that the risk of corrosion is avoided as the metal tank is not directly exposed to the water.
During thermal expansion and volume increase, water enters the expansion tank, moving the diaphragm and compressing the air out to create space for additional water. Any air that enters with the water is then removed from the system into the atmosphere. With these types of expansion tanks, you can prevent the harmful effects of thermal expansion on your water heating system and ensure that it operates efficiently for years to come.
How to Size and Select the Right Expansion Tank for Your Water Heater
When selecting an expansion tank for your water heater, it’s crucial to choose the correct size to safely handle thermal expansion. The right size depends on the capacity of your water heater and the pressure of your plumbing system.
If you’re replacing an old expansion tank, it’s generally best to select one with the same size as the previous unit. However, if you’re purchasing a new one, you’ll need to determine the appropriate size based on the following two key factors:
- Capacity of the Storage Tank
- Pressure of the Plumbing System
Once you have this information, visit the manufacturer’s website to select an expansion tank that meets these specifications. You can also use sizing calculators to make the process easier. For example, the Westank.com website offers a convenient online calculator where you’ll need to provide details such as:
- Water heater volume (capacity)
- Low temperature of incoming water
- High temperature or maximum outgoing water temperature
- Initial water pressure
- Final desired pressure
Most residential expansion tanks typically range between 2 and 5 gallons in capacity. While it’s essential to match the size to your system’s needs, it’s often better to choose a slightly larger one than needed. Oversizing the tank ensures it functions properly without causing pressure issues, while undersizing can lead to excess pressure and frequent relief valve discharge.
Popular brands such as Amtrol, Watts, and Falcon can be found on Amazon, offering a wide selection for various water heater capacities.
Remember, proper sizing is vital for ensuring your expansion tank works efficiently and safely.
When Should I Replace My Water Heater Expansion Tank?
Expansion tanks for water heaters should be checked periodically to ensure proper functioning. Common signs that it’s time to replace it include:
- Water leakage: Leakage from the expansion tank can be a sign that it’s damaged or no longer functioning correctly. If you notice water dripping from the tank, it’s time to replace it.
- Age: Like most components of a water heating system, they have a lifespan. Most devices last between five and ten years, so if your tank is reaching its maximum lifespan, it’s wise to replace it.
- Low water pressure: A malfunctioning tank can lead to decreased water pressure in your plumbing system. If you notice a drop in water pressure, check the tank to ensure it’s functioning correctly.
- Inconsistent water temperature: A device that’s no longer working properly can cause the water temperature to fluctuate or become inconsistent.
- Increased water bills: A malfunctioning expansion tank can cause your water bills to increase. If you notice a sudden increase in your water bills, it’s worth checking the device to ensure it’s functioning correctly.
By knowing when to replace a water heater expansion tank, you can ensure that your water heating system is operating correctly and efficiently.
How to Replace a Water Heater Expansion Tank
Replace a water heater expansion tank following the steps below:
- Turn off the power to the water heater: Before you start replacing the unit, turn off the power supply to the water heater. If you have an electric heater, switch off the power at the circuit breaker. If you have a gas heater, turn off the gas supply.
- Turn off the water supply: Turn off the water supply to the water heater by closing the valve on the cold water supply pipe.
- Drain the water heater: You need to drain some water from the tank to relieve the pressure and make it easier to replace the expansion tank. Connect a garden hose to the drain valve at the bottom of the heater and run the hose to a nearby drain or outside.
- Remove the old device: Use a pipe wrench or adjustable wrench to disconnect the old part from the water heater. If it’s a bladder type tank, carefully depressurize it first by opening the valve on top.
- Install the new one: Install the new expansion tank by threading the nipple fitting into the opening on top of the tank. Make sure the tank is oriented in the correct position and that the Teflon tape or joint compound is applied to the threads.
- Reconnect the water supply: Reconnect the cold water supply line to the water heater, using Teflon tape or joint compound on the threads.
- Turn the water supply back on: Open the cold water supply valve and turn on a hot water faucet to allow air to escape from the system.
- Check for leaks: Check all the connections and joints for leaks. If there are any leaks, tighten the connections or replace the faulty parts.
- Turn the power back on: If you have an electric heater, turn on the power at the circuit breaker. If you have a gas heater, turn on the gas supply and relight the pilot light.
- Test it: To test the expansion tank, start by turning on the water heater and letting it heat up. Check the pressure gauge to ensure it falls within the manufacturer’s recommended range. Next, test the pressure relief valve to confirm it’s functioning properly. Tap both the upper and lower parts of the tank— the upper part should sound hollow. If you hear a thud, the upper chamber may be filled with water, indicating a damaged diaphragm. Finally, check the temperature of the tank’s surface. The top should be cool, indicating air, while the bottom should be warm, where the water is stored.
Conclusion
Replacing a water heater expansion tank is a simple process that can be done with basic plumbing tools. It’s important to choose the right unit size for your water heater and to follow the manufacturer’s instructions for installation. Proper installation and maintenance can help prolong the life of your water heating system and prevent damage from extreme pressure. If you are not comfortable with installing an expansion tank yourself, it’s recommended to hire a professional plumber to ensure that the work is done correctly and safely.
FAQ
Expansion tanks are required by plumbing codes in most regions for closed-loop water heating systems. The codes mandate the use of such devices to protect the plumbing system and prevent water damage due to thermal expansion. The requirements for installation vary depending on the local plumbing codes and the type of water heating system installed.
You may need to replace your water heater expansion tank if you notice that the pressure relief valve on the water heater is spurting water, or there is extreme pressure on the gauge, or the expansion vessel is full of hot water. Additionally, if you notice any leaks or corrosion on the tank, it may need to be replaced.
Replacing a water heater expansion tank is a straightforward plumbing work that typically takes about 30 minutes to complete. However, the time it takes to complete the installation may vary depending on the type of pipes in the system and the specific installation requirements.
