Hard water can play havoc with tankless water heaters. But by taking a few precautionary actions you'll not only save money, you can also prevent a major headache. Water hardness varies by geographical location, and the level of hardness is determined by the amount of dissolved minerals within the water supply.
Water that's relatively pure and mineral free is called soft water. Rain water starts out as soft water, but as it's absorbed into the ground, the water travels through 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 considered to be a health concern, hard water definitely causes problems for many of your home appliances.
As the hard water passes over the surfaces within your home, the minerals begin to separate from the water. Over time, the separated minerals form a scaly layer called limescale.
Water heaters are prone to limescale build-up, but so are sinks, dishwashers, washing machines, and even showers. Basically, anything that comes in contact with water can develop limescale.
Importance of Descaling your Tankless
Both tankless water heaters and tank-style water heaters are negatively impacted by limescale build-up from hard water. But with tankless systems the unit's expensive heat exchanger needs to work harder than necessary in order to heat the water.
Since the heat exchanger becomes caked with limescale it's no longer capable of efficienctly transferring heat to the water. In order for water to reach the desired temperature, the heat exchanger needs to go into overdrive.
Effects of Limescale:
- The heat exchanger will need to work harder to heat water because its 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 may need to be called to get the unit up and running again.
- As limescale build-up increases, the heat exchanger's burner cycles also increase in order to compensate for the lost efficiency. When this happens, the tankless is no longer saving you money on your fuel bills because of its lack of efficiency.
- Manufacturer warranties do not cover damage caused by limescale build-up.
How to Remove Limescale Build-up
The good news is, once limescale build-up forms, it can be removed by flushing. Flushing a tankless water heater is critical to keeping it operating at it's peak performance, and to help it reach it's service life potential. Regular flushing is especially important if you live in an area with hard water.
Manufacturer recommendations vary, but most suggest flushing your unit every 12 months. Although, keep in mind that, in the end, the frequency should be based on the area's water hardness.
Purchasing a set of inexpensive test strips can help you check the mineral content of your water. Consulting with a professional can also be helpful, as he can give you his recommendation for the flushing frequency in your area.
Although limescale can be removed from your tankless water heater by regular flushing, the best solution is to prevent it from forming in the first place. Being pro-active can greatly reduce the affects of hard water. Below are a few options to consider:
Scale Inhibitor Systems
A scale inhibitor system is a relatively inexpensive way to protect water heaters from hard water. This system allows water to pass through a filter before it enters the water heater. To make changing the filter easy, a shut off valve should be installed on the pipe on each side of the filter.
As the hard water enters your home, it will pass through the scale inhibitor filter BEFORE it flows into the water heater. This type of filtration system reduces limescale build-up by preventing minerals from bonding to the metal surfaces.
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Salt Based Whole-House Water Softeners
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 often the most affordable way to treat water. These systems completely remove the calcium and magnesium from the water as it passes through the water softener.
The calcuim and magnesium is replaced with sodium ions, which is done by binding negatively charged potassium, sodium or hydrogen resin to positively charged metal ions. In other words, the hard minerals are literally drawn from the water.
As hard water enters your water softener, it flows through resin beads which attracts and traps the hard mineral molecules. When the water enters your home, it's mineral free and considered soft.
Over time the resin beads eventually are "full" of the hard water minerals. In order for the system to continue to soften your water, it'll need to run through a process called regeneration.
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Salt Free Whole-House Water Softeners
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 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 through in a stabilized state leaving them unable to form limescale.
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Electromagnetic systems alter the ions of hard water minerals as the water flows through 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 water. However, there is some debate on the effectiveness.
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Whether your water heater is tankless or tank-style, dealing with the affects of hard water requires a proactive approach. The methods shown above can help protect your water heater from limescale, and regular flushing will remove any limescale that has formed.
But which water heater is best suited for handling hard water? Well, this question can be a little misleading. If you live in an area where hard water is a concern, first and foremost consult with a professional.
The money and time you spend upfront for a professional's expert advice is well spent. He'll not only be able to help you find the right water heater for your situation, but he can also suggest the best filtering system for your area.
Selecting the Best Water Heater for Hard Water
Have you ever heard the saying, "You get what you pay for"? It may an old saying, but this general rule applies to purchasing a new water heater.
Higher-end water heaters are manufacturered with better quality materials and components, and purchasing a system from a reputable manufacturer can ensure good customer service for years to come.
That's not to say, that you shouldn't help your water heater battle the affects of hard water, but a higher-end system may be a bit more forgiving. Here are a few units you may want to consider.
Our Picks for the Best Hard Water Tankless Water Heaters
Stiebel Eltron Tempra 24 Plus Electric Tankless
Stiebel Eltron has a large line of tankless water heaters. The Tempra 24 Plus may be the mid-sized unit in the line-up, but it's more than capable of delivering plenty of hot water to your household. With 24kW's, the Tempra 24 Plus can deliver a flow rate of 3.64 gpm with an incoming water temperature of 45°.
With it's sleek good looks and superior German engineering, Stiebel Eltron is an excellent choice. The Advanced Flow Control means you won't need to worry about running out of hot water when demand is higher than expected.
There's no need to hide this water heater in the basement, not only does it look good, but it runs virtually silent. And since it doesn't need to be vented, it can be installed nearly anywhere!
- Uses the German patented Advanced Flow Control, which automatically reduces the flow of hot water in order to maintain the temperature when the demand exceeds the system's capacity.
- Solid copper heating modules.
- Pre-set temperature memory buttons and a digital display that monitors the temperature and usage of the unit.
- Quality comes at a price. Although less expensive than a gas tankless water heater, the Tempra 24 Plus is on the higher-end of the price scale for an electric tankless water heater.
Rheem RTEX-24 Electric Tankless
The Rheem RTEX-24 is an excellent choice if your looking for a whole house electric tankless water heater. It's capable of delivering a flow rate up to 5.9 gpm, but if you need a more powerful unit, there are plenty of others in the RTEX to choose between.
Rheem is a top-notch brand, and their RTEX line-up is a favorite among consumers and professionals. Although the RTEX-24 is capable of servicing up to 3 showers running simultaneously, proper sizing is critical to your geographic area. If you purchase a unit too small, you'll most definitely be unhappy.
You'll have plenty of installation options with the RTEX-24. It doesn't require venting so it can be installed nearly anywhere. The sharp, clean lines and classy finish means you don't need to tuck the unit out-of-sight. This is an excellent choice, and with proper maintenance, it'll last a very long time.
- The electronic temperature control is easy to read and allows the unit to make 1° adjustments. Temperature settings can be made between 80 to 140°F.
- Three Copper immersion heating elements are not only durable, but are threaded with a brass top for easy replacement.
- Advanced self-modulation system can deliver 99.8% energy efficiency because it adjusts the power up or down to meet the hot water demand.
- Professional installation is recommended. Although, this is an additional expense, electric tankless water heaters are easy to install and having it done by a professional will give you peace of mind that its done correctly.
Rinnai RUR199iN Gas Tankless
The Rinnai RUR199iN is a powerful gas tankless water heater. It has all the bells-and-whistles you'd expect from a premium brand and it's capable of delivering up to 11 gpm of hot water. It's also the direct and updated replacement for the RUR98iN model.
It's hard to go wrong with a Rinnai and the RUR199iN is an excellent choice. With one hundred years of experience behind the company, and one of the best warranty's in the industry, Rinnai has earned a reputation of being the best of the best. In fact, the average service life of a Rinnai is 20-years!
If a part needs to be replaced, it can easily be swapped out with a new part. No need to purchase a whole new heating system. Although professional installation is strongly encouraged, that is the norm for all tankless water heaters. The RUR199iN has multiple venting options and does not require expensive Category III material, making installation easy for a professional.
- This unit is ideal for homes without a dedicated return line. The ThermaCirc360 technology means you'll have hot water fast due to the built-in recirculation pump, timer and thermal bypass valve.
- The Uniform Energy Factor of .93 means nearly all of the energy used is going to heat your water. This is a very high score for a gas tankless and one of the reasons this heater is ENERGY STAR certified.
- The included Control-R Module allows you to control the RUR199iN from an app on your phone. Adjust the temperature, activate recirculation, and even allow for remote monitoring with a professional for maintenance or troubleshooting. With Control-R you'll be able to control your tankless even if you're on vacation!
- The RUR199iN is a premium tankless water heater, but it's not inexpensive. It'll definitely add to the resale value of your home, but if you're planning on moving soon, it may not be worth the investment.
- Professional installation is recommended, and if your a DIY kind of person, keep in mind that improper installation may void your warranty.
Rheem RTGH-95DVLN-2 Gas Tankless
Part of Rheem's Prestige model line-up the RTGH-95DVLN-2 is the updated version. The main difference between the two models is a more powerful fan which enabled Rheem to reduce the intake air and exhaust vent ports from 3-inches to 2-inches.
This high efficiency gas tankless water heater is designed for indoor use, although thereis a propane fueled unit and outdoor models in the same line-up.
With a pre-wired digital remote control, built-in condensate neutralizer, and an ultra low NOx burner the Rheem RTGH-95 DVLN-2 is ready for the most challenging hot water households. The unit is also capable of operating in altitudes up to 8,400-ft above sea level.
This environmentally friendly tankless has a Uniform Energy Efficiency rating of .93, which is an impressive rating for a gas unit. The heating chambers are made of stainless steel, and the self-diagnostic system alerts you to maintenance and repair requirements.
- Freeze protection to -30° allows you to install the unit in garages and basements without worry.
- Rheem's exclusive Hot Start Programming minimizes cold water bursts by keeping the unit in a ready-fire state when back-to-back hot water is needed.
- Connect to the EcoNet mobile app with the Tankless EcoNet Accessory Kit and you'll be able to monitor and adjust your tankless, as well as receive service alerts.
- Although the unit is EcoNet Enabled and Circulation Pump ready, these extra features are not included and need to be purchased separately.
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Last update on 2021-06-11 / Affiliate links / Images from Amazon Product Advertising API