What Happens if You Don‘t Have an Expansion Tank on a Water Heater?

Installing an expansion tank on your water heater is critically important for maintaining proper water pressure and preventing potential damage to your plumbing system. But what exactly happens if you don‘t have an expansion tank connected to your water heater?

How Does an Expansion Tank Work?

Before we look at the consequences of not having an expansion tank, it‘s helpful to understand what an expansion tank does.

An expansion tank is a small tank that is installed on the cold water supply line leading to the water heater. As hot water is generated and stored within the water heater tank, it expands in volume. This expansion of hot water causes an increase in pressure inside the tank.

The expansion tank gives the expanding water a place to go, allowing it to flow into the tank when the pressure gets too high. This regulates the pressure and keeps it within a safe range. The expansion tank includes a bladder or diaphragm inside that compresses as the water flows in, providing even more space for the excess water volume.

Without an expansion tank, there is nowhere for this expanded hot water to go as it builds pressure. This leads to a number of potential issues:

Plumbing System Damage

The sudden increases in water pressure caused by thermal expansion can put a great deal of stress on the pipes, joints, valves and fixtures in your plumbing system. Over time, this added stress can cause pipes to leak or even burst, and damage appliances like dishwashers and washing machines connected to the plumbing.

The expansion puts strain on every connection point in the system. Copper pipes may start to bulge and leak at soldered joints. PEX piping could separate at fittings. Supply lines to fixtures could leak or burst. Valves and appliance supply hoses are also vulnerable.

This type of plumbing damage often leads to costly repairs and water leaks or flooding within the home. Installing an expansion tank helps protect your plumbing by absorbing these pressure fluctuations.

Relief Valve Operation

If the pressure builds high enough, the water heater‘s temperature-pressure relief valve will open to release some of the pressure. This valve serves as a safety mechanism to prevent an explosion or rupture of the water heater under excessive pressure.

However, when the valve has to operate frequently to lower pressure due to lack of an expansion tank, it wastes large volumes of hot water. All the water released out the valve is dumped down the drain.

This can increase your energy and water bills, as the water heater has to work harder to keep heating more water. Frequent relief valve operation also leads to premature failure of the valve itself over time.

Higher Risk of Damage to the Water Heater

The constant pressure fluctuations also put a great deal of stress on the water heater tank and internal components. This leads to more wear and tear over the years. The risk of leaks or cracks in the tank developing increases without an expansion tank to help regulate pressure.

Damage to components like heating elements is also more likely over time when subjected to repeated pressure spikes. This can lead to premature water heater failure or loss of efficiency.

Increased Water Hammer

Water hammer refers to the loud banging noises that can sometimes be heard in the pipes when a valve is closed suddenly. This rapid closing of a valve causes a pressure wave through the plumbing system. Without an expansion tank, this effect is intensified.

Water hammer can result in considerable damage to fixtures and pipes over time. The vibrations from the pressure waves weaken joints and components. Loud banging noises are also very annoying for homeowners when they occur.

Higher Energy Costs

The frequent opening of the relief valve and added strain on the water heater caused by uncontrolled pressure both lead to increased energy usage. More energy is required to keep reheating water being dumped out the relief valve.

Stress on the water heater components also reduces heating efficiency over time. Installing an expansion tank helps optimize water heater operation and reduce wasted energy.

Potential Damage to Fixtures

The surges in water pressure may also end up causing damage to fixtures like faucets, showerheads and toilets as well. If the pressure spikes are frequent and extreme enough, components in fixtures can weaken and eventually fail.

How an Expansion Tank Prevents These Issues

While the expansion tank may seem like a minor component, it is absolutely vital for the health and safety of your water heating system and plumbing. By providing a place for expanded hot water to go, the tank helps regulate pressure within a safe range.

This both prevents damage and optimizes the efficiency of your water heater. Installing an expansion tank is mandatory in most areas today for any new water heater installation for these important reasons. Retrofitting an older system with a tank is highly recommended.

Expansion Tank Life Expectancy

The life expectancy for a water heater expansion tank will vary based on the quality of the tank, proper installation and maintenance. On average, expect a lifespan of 10-15 years for a tank in good operating conditions.

Higher quality tanks may last up to 20 years or longer. Tanks that are exposed to particularly high pressures, corrosion, leaks or sediment buildup tend to fail sooner.

Here are some key factors in the lifespan of an expansion tank:

• Tank construction – Tanks made from higher quality materials like stainless steel typically last longer than cheaper steel tanks prone to rust and corrosion. The thickness of the tank walls also impacts durability.

• Water pressure – An expansion tank constantly exposed to very high water pressures will weaken over time and require earlier replacement. Proper sizing for the pressure is key.

• Water quality – Harsh water with high mineral content can corrode and degrade the expansion tank more rapidly.

• Installation – Improper tank installation that leads to added stresses or excess sediment accumulating in the tank will shorten its lifespan. Proper installation per manufacturer guidelines helps maximize longevity.

• Maintenance – Regular inspection, sediment draining and addressing any leaks or corrosion issues lengthens the usable life of the expansion tank. Lack of maintenance leads to premature failure.

• Environment – Exposure to freezing temperatures, humidity, sunlight or other extreme environmental conditions can accelerate wear and degradation of the expansion tank.

With high quality components, proper sizing and installation, and regular maintenance, an expansion tank can often operate for 15-20 years before needing replacement. But budget for a shorter lifespan of 10-12 years under average conditions. Monitoring and inspecting the tank yearly allows you to address any issues early.

Signs It‘s Time to Replace an Expansion Tank

If your expansion tank is more than 10 years old, be on the lookout for any of these warning signs that indicate it‘s time for a replacement:

• Visible corrosion or rust
• Cracks or leaks in the tank shell
• Bladder is visibly waterlogged or showing signs of failure
• Reduced or substandard water pressure
• Relief valve on the water heater engaging frequently
• New banging or water hammer noises
• Unexplained leaks or flooding in the home

Replacement is strongly recommended whenever you notice any of the above issues to prevent further damage to your plumbing system. Catching a failing expansion tank early on avoids major headaches down the road.

Cost to Install an Expansion Tank

The cost to install a new expansion tank will depend on the complexity of the job, your geographic location, and local labor rates. But expect to pay $200-$600 overall for the typical installation.

Here are the costs ranges for basic components in an expansion tank installation:

• Expansion tank – $80-$300 depending on size, construction and pressure rating

• Connector hoses, valves, fittings – $50-$150 total

• Labor – $70-$150 per hour (2-3 hours typical)

In some cases, additional costs may be required if more extensive modifications to existing plumbing are needed to accommodate the expansion tank. And if the installation is part of a larger re-plumbing job or water heater replacement, this will also impact the total work required and pricing.

But for a straightforward expansion tank installation, budget $200-$600 in most cases to have a professional handle the job. This upfront investment will pay dividends in preventing costly damage down the road.

Choosing the Right Size Expansion Tank

Selecting the proper size expansion tank for your water heating system is important to allow it to properly handle thermal expansion. Here are the key factors to consider:

• Water heater capacity – The size of your water heater storage tank (in gallons) determines the maximum volume of expanded water to account for.

• Water pressure – House water pressure determines the amount of pressure the tank must be able to handle. Information on your pressure should be obtained from the water supplier.

• System piping – Total length of the supply piping affects required expansion tank sizing. Longer runs require a larger tank.

• Water heater construction – Tankless systems require smaller tanks, while older steel tanks with higher heat retention call for larger sizing.

As a general guideline, the expansion tank size should be around 10% of the water heater capacity. So a 40 gallon water heater would need a 4 gallon expansion tank.

But this must be adjusted based on your specific system pressure, piping and water heater type. Consult manufacturer sizing guidelines to select the optimal expansion tank size for your installation. An undersized tank will lead to pressure issues.

Choosing an Expansion Tank Location

The ideal location for your expansion tank is on the cold water supply line leading into the water heater. The key considerations for choosing the best location include:

• Place the tank close to the water heater inlet, preferably within 5 feet. Longer distances reduce effectiveness.

• Ensure it is easily accessible for servicing and maintenance.

• Mount it securely to studs or rafters using the provided straps or bands.

• Position vertically upright for proper drainage and sediment removal.

• Allow a minimum of 8" clearance beneath the tank for water drainage.

• Keep it protected from freezing temperatures if installing in a garage or basement.

Installing the expansion tank too far from the water heater inlet or in a difficult to access spot will make maintenance harder down the road. Follow manufacturer guidelines for proper placement to maximize performance.

Installing an Expansion Tank Without Draining the System

For installations in an existing water system, specialized expansion tanks that do not require draining the plumbing are available. This avoids the major hassle of draining all supply lines and the water heater.

Instead, these tanks have an external connection for a garden hose that is used to fill the tank with air to the proper pressure before installation. Models like the Wessel Tankless Expansion Tank allow full integration into the plumbing system without drainage.

Air is pumped into the tank through the external port until the air pressure matches that of the water system. The hose is then removed and the tank is ready for installation. This air pre-charge allows the tank to immediately absorb thermal expansion.

Using this style of expansion tank greatly simplifies retrofitting an existing system. Just be sure to purchase an expansion tank designed specifically for filling externally without drainage. The installation instructions will provide full details on the process.

Installing an Expansion Tank on a Well System

Homes on well water systems also require expansion tanks to control pressure fluctuations. However, these systems have additional considerations:

• Purchase an expansion tank designed for well system applications, which feature higher pressure ratings, stainless steel construction, and sealed diaphragms.

• Install a pressure reducing valve just before the expansion tank inlet to regulate excessive well system pressures down to 50-60 PSI.

• Install an in-line filter ahead of the expansion tank to remove sediment that could foul the tank.

• Install an air volume control tank downstream of the expansion tank to handle water slugs from the well pump and smooth out the system.

• Set the expansion tank‘s pre-charge air pressure to 5 PSI under the pressure reducing valve setting (e.g. 55 PSI if reducing to 60 PSI).

With a pressure reducer, filter, air volume tank and properly-sized expansion tank, well systems can effectively control thermal expansion and water pressure spikes.

Installing an Expansion Tank on a Solar Water Heating System

Solar thermal systems reach extremely high temperatures and require an extra-capacity expansion tank. A tank that is 20-30% of the solar storage tank size is recommended in solar thermal applications.

Additional considerations for expansion tank installation in solar water heating systems include:

• Use an expansion tank with the maximum pressure and temperature ratings for safety.

• Ensure the tank material (e.g. stainless steel) is compatible with ultra-high temperatures.

• Install an electronic expansion valve to allow automatic water discharge as a secondary pressure control.

• Set the expansion tank‘s pre-charge pressure very close to the solar water pressure under normal operation.

• Install an isolation valve between the solar storage tank and expansion tank for easier servicing.

Properly installing oversized expansion tanks on solar thermal systems allows stable and safe water pressures even under intense solar heating.

Installing an Expansion Tank for a Hydronic Heating System

Hydronic heating systems also require expansion tanks to handle heating/cooling cycles. Installation tips include:

• Install the expansion tank on the return line so the air rises into the tank.

• Mount the tank above the highest radiator or heating coil to prevent air pockets.

• Select a tank size of around 10% of the total system water volume.

• Set the tank‘s pre-charge pressure just below the system‘s static fill pressure.

• Ensure the tank meets the maximum temperature of the hydronic system.

The expansion tank helps smooth out pressure fluctuations during heating/cooling cycles and allows air removal. This leads to quieter, more efficient operation of the hydronic system.

Takeaways on Expansion Tank Installation

Installing a properly-sized expansion tank is critical to prevent pressure spikes that can damage plumbing systems and water heaters. Follow these guidelines for optimal expansion tank performance:

• Size the tank based on factors like water heater volume, water pressure, and piping length

• Install on the cold water inlet within 5 feet of the water heater

• Mount it vertically with clearance for drainage

• Use external fill models for easier retrofitting without drainage

• Adjust sizing, pressure settings, and location for well systems or solar applications

With a quality expansion tank professionally installed in the ideal location, you can avoid costly plumbing repairs and keep your water heater operating safely and efficiently. This affordable upgrade should be standard in every home.