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How to Prevent Scale in Tankless Water Heaters

by Mark Timmons August 03, 2017 25 Comments

Tankless water heaters are gaining popularity all over the country for a variety reasons, but the Top Two Reasons undoubtedly are (1) saving money on energy; and (2) never running out of hot water. To me, unlimited hot water is the biggest deal. If you have several persons in your family, especially teenagers who may take long showers, then you know that the last man (or woman) often gets a cold shower. That doesn't happen with a tankless water heater. If you decide you want to take a shower at 8 AM and stay in there until lunch, the water will be hot. You might look like a prune… but the water will stay hot. What's not to like about that? The only drawback to a tankless water heater, other than the initial cost, is that they are very sensitive to limescale buildup. This is a major problem in certain parts of the country and not such a big deal in others. Here's the most important thing however: Even a small amount of limescale buildup will impact the efficiency and economy of any tankless water heater. A sixteenth of an inch build up could end up costing you hundreds of dollars a year in energy costs, and cut the life of the tankless water heater by several years. Limescale forms when water which has a significant amount of hardness is heated, like in a tankless water heater. A physical reaction occurs whereby the hardness minerals precipitate out and form the hard and destructive limescale. One way to prevent limescale in a tankless water heater is with a water softener. A water softener removes that hard minerals - calcium and magnesium, from the water so that no limescale can form. Battelle Memorial Institute did a research study on water heating with hard and soft water and concluded, in part:

“Battelle concludes that use of a water softener to reduce the scale forming compounds in water will result in natural gas savings. This natural gas savings will lead to direct economic savings. Because of the need to have the instantaneous water heater delimed or cleaned periodically, the economic savings can lead to recovery of the cost of a water softener and operating supplies in a period as short as months, if the inlet water is sufficiently hard. Further, the lower use of natural gas leads to reductions in the carbon footprint…”

For many years, people have utilized water softeners to prevent scale in water heaters, pipes and appliances. Added benefits of using a salt-based water softener include the following:

  • Approximately 50% less soaps, detergents and cleaning agents are required with softened water.
  • Clothes are softer, whiter and brighter with softened water.
  • Skin and hair are dramatically impacted for the better when washed in softened water.
  • Less cleaning is required in showers and fixtures.
  • Spots are eliminated in the dishwasher.

However, not all consumers want a water softener that uses salt, even though the new generation of water softeners are up to 75% more efficient on salt. For example, the Fusion NLT Commercial Water Softener uses up to 75% less salt and water. This has caused many marketing companies to develop products that they sell to the unsuspecting public, called “salt-free water softeners.” They extol their products as new technology that softens the water without salt. They even say “It softens hard water, but leaves the beneficial minerals.” That is a contradictory statement - if you leave the beneficial minerals, you do not soften the water. The only way you can soften the water is by removing the minerals. End of story. You can't have it both ways. Saying that they have a salt-free water softener which leaves the minerals is a physical impossibility - it is also a blatant lie! A lie that they tell to get people to buy their products. There is no such thing as a “salt-free water softener"! They do not soften the water. They do not exist. They are merely a figment of a marketing persons' imagination. It is physically impossible to soften water while leaving the beneficial minerals. How some of these companies get away with these "lies" is beyond me. Happily, you do not have to have a salt-based water softener to protect your water heater, pipes and appliances, although you will not get the benefit of soap savings and the like. There are several salt free water conditioners on the market and unlike water softeners which removes the calcium and magnesium, a conditioner attempts to neutralize the limescale. What I mean by this is that a salt-free conditioner attempts to put the hard minerals in a situation where they will not form limescale. What we have found it that it is a very "inexact science," and when I use the word "science" I am being kind. What we have found is that fully 25% to 50% of the salt-free systems do not work as promised. That is an astounding number! Then you need to consider the "lunatic fringe" who are people that believe anything you tell them and endorse it wholeheartedly - that is a monstrous number! If you factor that in, the reality of the matter is that as few as 25% of the salt-free conditioners work and of course - 100% of the salt-free softeners do not work! So, if you want to prevent limescale in your tankless water heater but don't want to use a salt based water softener, what should you do? Well, you could call the guys who say they have salt-free softeners, when they don't, or you can call the company America trusts to tell them the truth about your water. If you do, we are going to tell you that while our salt-free conditioner does not soften the water, it does do a tremendous job at preventing and removing existing limescale in water heaters, pipes and appliances. The systems is the US Water Systems Pulsar Limeblaster, which does exactly what it is called - it blasts away the lime scale! The Pulsar Limeblaster is the new revolutionary and economical way to fix hard water. The Pulsar Limeblaster totally prevents limescale on and in appliances, pipes, fixtures - actually everything water touches. Our new Limeblaster System is the new standard by which all salt free water conditioners will ultimately be judged. The new Limeblaster technology effectively "Seals" the plumbing and appliance surfaces so that calcium and magnesium (often called limescale) cannot stick. Additionally, the Limeblaster water treatment method is environmentally friendly, uses no electricity and is 100% safe for drinking water.

Here's the truth about limescale: Limescale is formed when cold water is heated in a water heater, boiler or tea kettle. In the process of heating water, such as in a water heater, calcium carbonate precipitates and forms limescale. We recommend installing the Pulsar Limeblaster on just the line to the water heater as the limescale does not form inside cold water pipes. About half the water used in a home is hot water, so the Pulsar Limeblaster cartridge lasts about twice as long as when it is on both the hot and cold supply. Of course, it is completely acceptable to install it on the entire home water supply. Operational costs are typically less than $50 a year and it does a remarkable job of preventing limescale, which is why we offer a one-year money-back Guarantee. If you want to protect your tankless water heater and don't want a water softener, get the next best thing... from people who tell you the truth!

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March 14, 2018 RyderDA

Getting a little bit frustrated here. You repeatedly pick on your competitor companies like Pelican for calling water “conditioning” water “softening”, and razz the them for misleading people by the language they use. Then you turn around and claim that your LimeBlaster “blasts” away lime, which it doesn’t. You say it “seals” the plumbing systems when it doesn’t. Pot. Kettle. Black.

You’re obviously correct that technologies like TAC and MEP and NAC do NOT soften the water, but research proves they DO prevent (or at least reduce) scale buildup — which is why your company has one of those systems, the LimeBlaster. It’s also true that research shows that introducing a TAC system can cause some of the existing scale to come off. I guess that’s why you think the LimeBlaster “blasts” lime.

I don’t want soft water. But I do want scale reduced. I can’t use salt for various reasons. And TAC technology will achieve that. Your products are among several on the market that make that, including Watt and Stiebel Eltron.

March 14, 2018 Mark Timmons

We used to use TAC, but no longer do so because the new Limeblaster technology works better. We used to have about 15% of the people who bought the TAC or NAC technology ask for their money back. Since switching to the Limeblaster technology, we have not had a single return request. It works that much better.

I am sorry that you think we are misleading people, but the fact is: when used continually on limescale, it does cause pieces of the limescale to “blast” away from the surface it is adhered to and it ABSOLUTELY seals the plumbing with Silphos polyphosphate to prevent scale formation. It seals the surface by forming a one-molecule thick coating (Silphos cannot stick to itself) which is fragile and continually needs to be replaced by the Silphos in the cartridge which needs replaced about every 6 months.

We liked the name Limeblaster and it actually does what it says. When you first start using it, it is common to see these pieces of lime that have been “blasted” away. Maybe the name is a little hyperbolic, but it’s not misleading and we need every advantage against people who totally obfuscate the truth.

June 02, 2018 packy


Make sure you test the well for other contaminates as well. I used to sell water treatment equipment here in AZ. some of our areas, atleast in the valley are very bad. Also, some areas like near the White Tank mountains are salty. Sucks when people install a softener on their well only to find that with the salty water, softeners don’t work. Remember that salt regenerates softeners.

August 16, 2018 Raylene

While I’m concerned about limescale forming in my tankless heater, it’s also clogging up the sinks and showers that are fed by the tankless heater. I don’t want it kept from adhering to the tankless heater but still clogging up the sinks and showers. So apparently I still need to get a salt unit, that will prevent formation of the limescale.

August 18, 2018 Mark Timmons

You should first get a water test. Contact one of our water specialists for details.

August 27, 2018 harold lock

if I install a water softener on the feed line to my tankless water heater will that take care of the scale build up?

September 03, 2018 Mark Timmons


November 08, 2018 Michelle

I’m considering a whole-house system for various reasons (tankless water heater, 2.5 bathrooms, 2 people). Is the best place to start ALWAYS a water test like this or are they not needed in some cases?

November 10, 2018 Mark Timmons

Measure twice – cut once!

I always recommend a water test!

April 04, 2019 John Fernandes

Last night me and my wife was arguing about cost of a tankless water heater. People says that it costs a lot compared to tank type water heater and as these units are active for almost all the time will they consume more power than a tank type heater? If you could help me on this then it will be great help.
We’re planning to buy it due to space issue and sometime it consumes too much time when we already running late.

April 05, 2019 Mark Timmons

If it’s gas, it probably saves money. I do not think electric models are as cost-effective. However, the good part is that you don’t ever run out of hot water.

Be sure to use good water!

August 14, 2019 Susan

I have a tankless water heater. I put in a presentment filter because our water is so hard. My kitchen faucet hot side just drips, have no hot water in sink in bathroom I have flushed the unit itself with vinegar. It has been a nightmare. Company is sending me a new unit but with no warranty because of the water.

August 15, 2019 Mark Timmons


March 23, 2022 Darrell Jones

If I have a municipal water supply do I still need a softener, even though the supply is filtered and treated?

June 27, 2022 Mark Timmons

It depends upon what is in your water. Municipal water varies greatly from area to area.

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