How To Protect Tankless Water Heaters From Hard Water

    Hard Water

    Hard water can play havoc with a tankless water heater and taking a few precautionary actions will not only save you money but also a major headache. Different geographical areas experience different levels of water hardness, which is determined by the amount of dissolved minerals within the water supply.

    Water that is relatively pure and mineral free is called soft water. Rain water would be considered soft water, but as it's absorbed into the ground the water travels thru soil and rock. Eventually, it finds its way to rivers, lakes and other bodies of water.

    As the soft rain water travels to its destination, it begins to absorb minerals from the ground. The more minerals the soft water absorbs, the harder the water becomes. Hard water contains a high concentration of natural minerals, calcium carbonate and magnesium in particular. 

    • Although, not a health concern, hard water causes problems for many home appliances. 

    As the water passes over surfaces within your home, these minerals will begin to separate from the water. Over time, the separated minerals will form a scaly layer called limescale. Sinks, dishwashers, washing machines, and even showers are all prone to limescale build-up. ​

    Why Descaling your Tankless Can Save it from Hard Water

    Both tankless water heaters and traditional water heaters are negatively impacted by limescale build-up. But with tankless systems  the unit's heat exchanger will need to work harder than necessary to heat the water. This is because the heat exchanger will become caked with limescale which will prevent it from transferring heat as efficiently.  

    Here are some of the affects of limescale:​
    • The heat exchanger will need to work harder to heat the water because it is caked with limescale. It will eventually overheat.
    • The heat exchanger will not reach it's service life potential and need to be replaced.​
    • An error code could be triggered to shutdown the unit. A professional plumber will need to be called to get the unit up and running again.
    • As the limescale built-up increases the heat exchanger's burner cycles also increase to compensate for the lost efficiency. The tankless is no longer saving money on your fuel bills due to the lack of efficiency. 
    • Manufacturer warranties do not cover damage caused by limescale build-up.

    Flushing a tankless water heater is critical to keeping it operating and reaching it's service life potential. Manufacturer recommendations vary, but most suggest every 12 months.​ But in the end, the frequency should be determined by the homeowner and the decision should largely be based on the area's water hardness. You can purchase these inexpensive test strips to check the mineral content of your water. 

    Solutions to Hard Water Problems

    Certainly flushing your tankless can remove limescale from the unit after it's already formed, but there are ways to reduce the amount of minerals within your water to help prevent the build-up in the first place. Here are some methods to take a pro-active approach to hard water:

    Scale Inhibitor System

    A scale inhibitor system is a relatively inexpensive way to protect water heaters from hard water. This system installs a filter on the water heater's incoming water supply. A shut off valve should be installed on the pipe on each side of the filter to make changing the filter easy.

    As the water enters your home, it passes thru the scale inhibitor filter BEFORE it flows into the water heater. This type of filtration system will reduce the limescale build-up by preventing the minerals from bonding to metal surfaces.  Watch the video on Amazon's sales page HERE to learn how a scale inhibitor system works. 

    Our favorite scale inhibitor system is manufactured by Aqua-Pure. Simply install it on the incoming cold water supply and it will provide protection to your water heater as well as all of your water-using appliances, faucets, shower heads and pipes.

    Salt Based Whole-House Water Softener

    Both salt based and salt-free water softeners are a good fit for areas with extreme hard water. All of the incoming water to the house is treated, both hot and cold, so all of your appliances, fixtures and plumbing will benefit.

    Salt based water softeners are probably the most affordable way to treat water. These systems will completely remove the calcium and magnesium from the water as it passes thru the water softener.​

    Calcium and magnesium is replaced with sodium ions, which is done by binding negatively charged potassium, sodium or hydrogen resin to positively charged metal ions. The hard minerals are literally drawn from the water. ​

    As hard water enters your water softener it flows thru resin beads. The resin beads attract and trap the hard mineral molecules, and as the water enters your home, it is mineral free and considered soft.

    Over time the resin beads eventually are "full" of hard water minerals. In order for the system to continue to soften your water it needs to run thru a process called regeneration.

    Fleck manufactures a whole house system that comes in a variety of sizes and even color options. Simply plumb it into place, add salt and it's ready to use. This is a more expensive option, but it's a quality product and more than capable of providing years of service.

    Watch the Video on Salt Based Water Softeners

    Salt Free Whole-House Water Softener

    Salt free water softeners are also commonly called water conditioners or scale inhibitors. They function very differently than salt based water softeners as the hard water minerals are not removed from the water. 

    They do, however, still help prevent limescale build-up. Here are the 2 common types of salt free systems:​


    The process used in these systems is called epitaxial crystallization, where the calcium is changed from a type that deposits limescale, to a type that does not. 

    The minerals are not removed from the water, but rather are allowed to pass thru in a stabilized state making them unable to form limescale. 

    Nuvo's Home Water Softening System lowers the PH level of water. Each cartridge is designed to filter approximately 35,000 gallons of water before it needs to be replaced. Many people love this system, but it's not for everybody.

    Watch the Video on Catalytic Salt-Free Water Softeners

    Electromagnetic systems alter the ions of the hard water minerals as the water flows thru a magnetic field. The majority of systems on the market can be used on both metal and plastic pipes. 

    This is an easy-to-use system and many homeowners like that no chemicals are used in the process of treating the water. However, there is some debate on their effectiveness.

    The Eddy Electronic Water Descaler is a popular choice if you are looking for an electromagnetic water softener. The company has been around for over 15 years and offers a 12-month, no questions asked return policy and lifetime repairs or replacement.

    Watch the Video on Electromagnetic Salt-Free Water Softeners