Yes, you still need an expansion tank. While a Pressure Relief Valve (PRV) manages incoming water pressure, an expansion tank absorbs the natural increase in water volume when it is heated. Together, they form a Closed System that protects your plumbing from costly damage.
You will need a Pressure Release Valve (PRV) and a Thermal Expansion Tank to regulate your water's pressure.
The thermal expansion relief valve can replace a water heater expansion tank because it functions similarly. Both products absorb the excess pressure in the plumbing system created by thermal expansion.
If you spot any potential warning signs, consider contacting a local plumber. A water heater expansion tank costs an average of $325 to install, and most people pay between $150 and $450 for the task.
Signs Your Home Might Need a Water Heater Expansion Tank
If your home has a closed plumbing system with check valves that prevent water from flowing back into the main supply line, thermal expansion can cause significant pressure buildup. Installing an expansion tank can help manage this pressure, protecting your plumbing and water heater from potential damage.
You may need a water heater expansion tank if you experience frequent discharges from the temperature and pressure relief valve, fluctuating water pressure, loud noises from the heater, or mineral buildup around plumbing fixtures.
However, on average, an expansion tank can last 5 to 10 years or even longer if properly maintained and inspected regularly. It is recommended to check the expansion tank for signs of damage or wear, such as leaks or rust, at least once a year and replace it if necessary.
To replace the expansion tank, you must drain the boiler system of water to avoid spillage and potential damage. Locate the drain valve on the boiler and attach a hose to direct water away from the area. Open the valve and allow the water to drain completely from the system.
The size of the water heater expansion tank you need depends on the capacity and pressure of your water heater. In general, for a 50-gallon water heater with a pressure of 60 psi, a 2-gallon expansion tank is sufficient.
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.
With electricity, the cheapest way to heat your water is through renewables. This includes heat pumps, solar thermal systems and solar panels (through solar PV optimisers/diverters). Although the heating of the water is extremely cheap, if not free, from these systems, the install cost is obviously high.
A 250-gallon propane tank holds roughly 200 usable gallons (due to the 80% fill rule). Depending on your appliance load: Light use (stove, water heater only): 6–10 months. Moderate use (heat + cooking + water): 2–4 months in winter.
Many older homes and water heaters were installed without expansion tanks because building codes didn't require them at the time. However, modern plumbing standards have changed, and the risks of thermal expansion are now better understood.
You should expect strong water pressure in your showers and faucets in that range when using properly-sized residential water pumps. Any lower than 40PSI and some shower heads won't operate very well. Any higher than 60PSI -70PSI and you'll have to be careful not to burst any pipes that aren't rated for high pressure.
Water expands when it is heated, so traditional water heaters require expansion tanks to accommodate the pressure. If the expansion tank didn't exist, then thermal expansion would lead to equipment failures and safety hazards.
Expansion tank replacement costs $300 to $800 on average, including professional installation. The total cost to replace an expansion tank depends on the tank size and type, labor rates, and your location. A boiler or water heater expansion tank costs $30 to $200 for the tank alone.
Typically, expansion tanks are located near the water heater, but can be placed on a cold water pipe anywhere in the home if there are no valves in between.
It is generally recommended that the expansion tank be installed in the cold water side. I've never actually seen a pro put one on the hot side. It isn't going to harm anything being on the hot side, but if it makes you uncomfortable, just ask him to change it.
A thermal expansion tank will need to be replaced once every 5 to 10 years. The best way to elongate the life of an expansion tank is to ensure the tank's pressure matches the incoming water pressure. If the pressure within the tank is too high or too low, it can cause the tank to fail.
Size of expansion tank will have no affect on water temp.
If you don't replace a bad expansion tank, excessive pressure can build up in your plumbing system, causing leaks, damage to your water heater, and potential pipe bursts.
If the expansion tank you purchase is smaller than what your system requires, the excess pressure from the expanding hot water will cause relief valve discharge. On the other hand, there is no problem with having an expansion tank that is larger than what your system requires.
A 40-gallon tank water heater installation costs $700 to $2,300, with an average cost of $1,650. Prices vary based on energy source and installation complexity. The national average cost to install a 40-gallon tank water heater ranges from $700 to $2,300.
Signs you need to install or replace an expansion tank