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Descaling Appliances: Which Acid is Best?

April 22nd, 2009

Acid is Dangerous!Those of you with hard water have no doubt encountered one of the most annoying problems ever: descaling appliances.

Sure, calcified bathtub superscum is also seriously annoying, but there are plenty of products out there that will magically descale and de-scum your bathtub with a few sprays and some waiting. It’s the appliances that are particularly annoying to clean – appliances like coffee makers and water distillers.

There are a number of different products available for removing rock-hard mineral deposits from your gizmos, but how do you know which one to use to make your life as easy as possible? You don’t! Otherwise, what the heck are you reading this for? But now you will know soon enough…

First of all, I should note that most of the acids I’m going to mention here are dangerous, and they will burn and horribly maim you if you aren’t careful. So, for the love of frickin’ Jesus, wear thick rubber gloves and safety glasses. Yes, you’ll look like a bonehead in your safety glasses, but that’s better than being blind. How do I know? Have I been blind before? No. But I have a blind friend, and he told me so.

The type of acid you should use depends on the appliance, the severity of the mineral deposits, and the materials from which the appliance is constructed.

For example, people generally clean coffee makers by brewing a nice fresh pot of vinegar. Vinegar contains acetic acid, which is a fairly weak organic acid. Nevertheless, sometimes acetic acid is enough.

In other cases, you may want to purchase a commercial iron/coffee maker descaling product. Normally, this type of product comes in liquid or crystalline form. The key ingredient is usually sulfamic acid, an organic acid that is used for all kinds of interesting things. Sulfamic acid is an excellent descaling agent, and it is much safer for various types of metals. When strong enough, it will even remove rust (try it!).

Sulfamic acid is, in fact, my acid of choice for most applications. When it comes to sulfamic acid, the crystalline white powder kind that comes in a packet is the best. The simple reason for this is that what you are getting is basically sulfamic acid and nothing else. You dissolve the crystals in water, and voila! You have a glorious descaling solution. There are also liquid descalers that contain sulfamic acid, but alas, they also contain other cleaning agents and stabilizers in order to keep the sulfamic acid in a liquidy state. Go for the crystalline stuff!

Now, sometimes, you have an appliance like a water distiller. Water distillers are fabulous contraptions for generating super-pure drinking water. Contrary to popular belief, drinking distilled water is NOT bad for you. I should know: I’ve been drinking nothing but distilled water for two years now, and I feel great! I am in perfect health. The reasons for why distilled water is actually good for you are beyond the scope of this post, but you can find a bunch of info on the subject by doing a simple web search.

In any case, water distillers for the home usually work by heating water with an electric element inside a sealed metal container. The water boils, the steam rises into a spiraling tube, a fan cools the tube, the pure water condenses, and it trickles down into the water reservoir. As you can imagine, what is left in the boiling chamber is a whole lot of nasty, crusty, rock-hard mineral deposits jam-packed with whatever other evil crapola is in your tap water. Cleaning those deposits is not easy, since it is literally rock hard.

This is where sulfamic acid comes in. It has to be VERY highly concentrated. In other words, dump in lots of packets of the white crystals! It works great, and it’s far more friendly for the metal boiling chamber and associated components.

However, sometimes, the mineral deposits are just too hard, or you don’t have hours to wait for the descaling process. In that case, go out and get yourself some hydrochloric acid, commonly known as muriatic acid. It’s the same stuff your belly uses to help digest food.

Hydrochloric acid is seriously evil stuff (except when it’s in your belly). You’ll see this for yourself when you catch a whiff of the noxious odors coming out of your calcified appliance when you pour in the diluted acid. Hydrochloric acid will eagerly eat through things like certain rubber seals, so be careful. It also has a bad habit of eating away at certain metals, so it must be used with caution. You don’t want to just willy nilly dump it full strength into some flimsy plastic reservoir and watch as your plastic container slowly dissolves. On the plus side, this is one acid that does not mess around with even the hardest mineral deposits.

Whatever acid you use, you will probably have to drain the acid, flush with water, and possibly use a metal utensil to poke and prod at any remaining deposits. They should just fall right off your appliance at that point. Flush with more water, and then place the gizmo back in service.

Of course, you can also use a container with acid in it to clean off calcified components, pipes or fittings, etc.

Stick with sulfamic acid if you can, since it’s the most friendly – in more ways than one. But whatever acid you use, be careful!!!

Do-It-Yourself ,


  1. Engr Ghulam Abbas
    December 6th, 2013 at 13:30 | #1

    Dear Descaler expert,

    I am quite impressed with your findings it is really very informative and you have given a birds eye view of acids use in very few lines it will definitely help the mankind.Keep it up keep sharing.

    Best Regards
    Ghulam Abbas Cyclewala(Chemical Engineer)

  2. Jabadahut
    December 10th, 2013 at 13:28 | #2

    Thanks mate

  3. Kwame Affum
    April 9th, 2014 at 15:19 | #3

    I love this info. However, for industrial application purposes, can you come out with dosage rate in terms of % or ppm or required pH for effective cleaning.

  4. Java Man
    April 30th, 2014 at 05:36 | #4

    I use muriatic acid to descale my commercial espresso machines. I buy it at home depot. I think it is 20% strength, but not 100 percent sure of that. I further dilute this to about 4 parts water to 1 part acid. In a plastic 5-6 gallon bucket I place the water first ****always water first***** then the muriatic acid. In a separate 5-6 gallon bucket, I just fill with water and dump in a large box of baking soda and mix it up. After about 5-7 minutes of soaking the parts with scale in the acid, I dip them into the baking soda (base) bucket. The baking soda neutralizes the acid and does an awesome job of removing the scale. Then I rinse with lots of water. I use wire coat hangers to attach to the parts to keep my hands away.Safety goggles are a must!!! When you dip the parts in to the base bucket, a chemical reaction occurs, and you get some violent splashing of the neutralizer and acid. I will say, it is fun! Yep…fun! Some boilers have a nickel coating on the copper, just be careful not to soak these parts for more than a few minutes, or the nickel coating will dissolve. Copper will melt away if left to long. If all of the scale doesn’t come off the first time, you can always resoak the parts. Just use short intervals to prevent damage.Common sense is key! At the end of my descaling, I pour the baking soda water into the acid bucket and this neutralizes what is in the bucket. This is the real fun! Just don’t wear nice shoes when you do this…Good Luck! Hope this helps.

  5. Selva
    June 20th, 2014 at 18:57 | #5


    Which will be a strongher acid between sodium gluconate Sulphamic Acid

    Currently I am using Hydrochloric acid & Sodium Gluconate. To clean oil coolers & Radiators



  6. Engr Ghulam Abbas Cyclewala
    July 7th, 2014 at 18:08 | #6

    Dear Selva,

    I have at times advised Phosphoric Acid , it does work faster and is safer than Hydrochloric Acid.

    Best Regards

  7. Selva
    August 15th, 2014 at 01:15 | #7

    Hi GA

    Thanks for your advise!

    Can I mix Phosphoric acid & sodium sodium gluconate together

  8. zia khan
    December 22nd, 2014 at 08:17 | #8

    what is optimum conceteration of sulfamic acid for using in RO unit as antiscaling agent

    • December 22nd, 2014 at 12:04 | #9

      I have no idea, but I solved the hard water problem by putting a water softener in front of the RO unit. Now the RO lasts forever. 😉

  9. Miti
    April 14th, 2015 at 18:46 | #10

    Hello Scotte, I wanna use Phosphonic(not phosphoric) Acid for Aluminium washing. Do you have any idea which kind of Phosphonic acid is better for this purpose?
    Thank you

  10. Chuck
    June 8th, 2015 at 20:14 | #12

    I’m on a quest to effectively clean, rather than replace, my humidifier filter belt! And I don’t like spending more money for products that are less effective than the basic ingredients they contain. Obviously one has to be careful using the strong stuff, but whatever works best, I want to know what it is. Your article has helped tremendously, thanks!

  11. July 26th, 2015 at 20:32 | #13

    I also use Muriatic Acid to clean with, because of the hard water here in Tampa.
    I dilute it one part acid to 4 parts water, and use it just like vinegar, followed by a couple of really good rinse brews.
    Use safety glasses, because you will hit the roof if it gets in your eyes during the cleaning cycle.

  12. Sandi
    March 10th, 2016 at 00:07 | #14

    I’ve got a hot tub that has a combination of heavy calcium scale & chlorine stains. Is there a safe & easy way to remove these stains without causing damage to the tub?

  13. Daryl
    March 16th, 2016 at 23:00 | #15

    CLR and other Sulfamic Acid containing cleaners are the best at removing heavy scale and stains. You’re not seeing chlorine stains but rather iron stains that are yellow and orange. Those cleaners can be quite irritating so make sure you have the bathroom fan running while you are using it. Spray the cleaner or apply it to a wet sponge and apply it so the entire surface is covered. Sulfamic Acid will not damage fiberglass or lined tubs but be careful as it will etch marble and probably other tile surfaces. Allow the chemical to work on the stain for 30 minutes or so and scrub after application. Rinse thoroughly before use.

    The key ingredient is Sulfamic Acid. For heavy hard water stains, foam cleansers, vinegar, Barkeeper’s Friend, and other relatively mild cleansers just aren’t effective.

  14. Daryl
    March 16th, 2016 at 23:03 | #16

    Be careful with that. Hydrochloric Acid is commonly used to strip chrome. It won’t affect the underlying nickel but if you strip the chrome the nickel will tarnish and discolor. No repair possible.

    @Chris Gerald Tucker@Apple Roof Cleaning


  15. Daryl
    March 16th, 2016 at 23:06 | #17

    Phosphoric Acid is Phosphoric Acid. You may be referring to the strength or concentration of the acid. I would think you could effectively clean aluminum with 5-10% /v Phosphoric Acid. Also try Naval Jelly which is available retail.


  16. Rory
    July 26th, 2016 at 01:40 | #18

    It’s not distilled water that is dangerous… It’s deionized water or water of higher, organic chemistry lab purity (MilliQ). These waters strip minerals from your system when consumed.

    Distilled water is just evaporated and recondensed. It still contains some minerals, included compounds it leaches from metal and plastic containers.

  17. Adrian
    August 17th, 2016 at 14:36 | #20

    Hi there! I have a laboratory water still that has a nickel element. I am currently cleaning it with HCl as the scale is 1 – 2mm thick. I would like to change to a weaker acid to prolong the nickel coating. Would you recommend sulphamic acid? (The scale is pretty thick)

    • August 17th, 2016 at 14:48 | #21

      Sulphamic acid is used in a lot of household cleaners at low concentrations, and it does appear to be safer (and weaker) than HCl. Well, I’m no chemist, but I’d give it a whirl!

  18. Adrian
    August 17th, 2016 at 14:54 | #22

    Thanks Scottie! Will let you know.

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