Do I need an expansion tank if I have a pressure tank? Yes, since they provide a different function, an expansion tank is recommended if you have a closed-loop system with any check valve or pressure regulating valve installed on the water supply line.
An expansion tank is required on the supply line coming into the tank to reduce the tank stress which will shorten the tank's useful life. An alternative to the expansion tank is an approved pressure relief valve assembly.
Short answer? If your home has a “closed” plumbing system, then yes, you'll need an expansion tank.
As plumbers know, the expansion tank equalizes pressure throughout the plumbing system by providing a space for hot water to flow into. Without an expansion tank, pressure would be distributed to the entire plumbing system, straining it and decreasing its lifespan.
Typically a 2-gallon expansion tank works with a water heater with a 40 to 60-gallon capacity and a psi of 40 to 50. A 4.5-gallon expansion tank is needed for larger water heaters, such as ones that hold 80 gallons with 80 psi.
If you are on a "Closed" loop water system, you will be required to have a Thermal Expansion Tank installed on your water heater, the next time it is replaced or repaired.
In general, most residential water heating systems with closed plumbing systems require an expansion tank to prevent damage caused by thermal expansion.
However, if a check valve or a pressure regulating valve (PRV) is installed on the water supply line coming into your home, it keeps all that excess pressure trapped in your home's plumbing system which stresses your supply lines, fixtures, and appliances. That's where the expansion tank comes in.
According to Forbes, the average cost of expansion tank installation is $220 (CAD 270) for materials and labor, with most homeowners spending between $90 and $350 (CAD 122 and CAD 473). Expect to spend between $40 and $200 (CAD 54 and CAD 270) for the tank itself, excluding the cost of labor.
When extra pressure builds up in the hot water system, it could cause pipes to burst, resulting in costly repairs and even greater risks if someone gets hurt. With an expansion tank installed, excess pressure is diverted away from pipes and other components which can help prevent accidents and damage.
Thermal expansion relief valves are an alternative to expansion tanks. Thermal expansion relief valves are typically a combination ball valve with a low-pressure, spring-loaded safety valve installed in the same place as an expansion tank.
Expansion tanks are pre-charged with a 40 PSI air charge. If the inlet water pressure is higher than 40 PSI,the expansion tank's air pressure must be adjusted to match that pressure but must not be higher than 80 PSI. *Highest recorded inlet water pressure in a 24-hour period of regulated water pressure.
But expansion tanks can wear out. The average life of your tank can be anywhere between five and 10 years. You can extend the life of your expansion tank by making sure that your home's water pressure matches the air pressure in your expansion tank.
Pressure tanks are generally 70% filled with air, so when you knock on the tank it should sound hollow and empty. If you knock on the side of the tank and it does not sound hollow and empty that is a good indication that it is waterlogged.
Be careful because these are often used interchangeably in the HVAC industry but there is a technical difference. Expansion tanks have bladders or diaphragms and the water expands into the tank “balloon”. Compression tanks do not have bladders; the air in the tank compresses as the water expands into the tank.
If your home has a Backflow Prevention Device, Pressure Reducing Valve (PRV), re- circulating pump with check valve, or anything else that prevents backflow of water installed, its plumbing system is considered "closed".
Expansion tank installation may be required by your local building codes when installing a new water heater, or it may be a retrofit project. Either way, it will involve splicing into the cold water delivery pipe above the water heater, and should only be taken on as a DIY if you have experience with plumbing work.
Unlike diaphragm tanks, steel expansion tanks do not separate the water and air inside. This means water inside the tank can absorb air, causing the water inside to expand. When water fills up too much space inside the tank, the pressure inside fluctuates, and the tank fails to operate correctly.
Whether you're adding a new expansion tank to an existing water heater or you are replacing a water expansion tank, you will need to drain your water heater. Various pipe connections have to be made and you don't want water to end up all over the floor, so drain the water heater before your work begins.
The alternatives to thermal expansion valves are fixed orifices and capillary tubes. These devices meter refrigerant as well, but they can't change size. That means they tend to starve the evaporator coil of refrigerant when cooling demand skyrockets, and flood it when cooling needs are low.
Water Heater Expansion Tank Costs
Most water heater expansion tanks come at a standard cost. The majority of the expense will depend on the tank's accessibility and other installation challenges. In most cases, you can expect to pay between $200 to $300 for your expansion tank.
Many homes built before certain plumbing codes were enacted may not have an expansion tank, as they were not a standard requirement. In older systems, open water systems allowed the expanding water to flow back into the city's water lines.
The California Plumbing Code (Section 608.3) and the California Mechanical Code (Section 1005.0) require a thermal expansion tank to be installed on all closed plumbing water heating systems.
A water pressure tank for a well is designed to help maintain adequate pressure in your pipes without requiring your well pump to run nonstop. A water heater expansion tank is designed for use on modern plumbing systems. You can find more detailed information on these two types of pressure tanks below.
A water heater expansion tank costs $150 to $450 on average, with a national average of $325. The total cost depends on the size and type of tank. A water heater expansion tank costs an average of $325 to install, and most people pay between $150 and $450 for the task.