We have very hard well water, and calcium carbonate builds up on wet surfaces like the inside of the toilet bowl (see photos at the end of the narrative). For years I used a product called “The Works” toilet bowl cleaner that removed tough calcium deposits, rust and other hard water stains from the toilet bowl really well. Then all of a sudden the stores stopped carrying it. For some months “The Works” was not on the shelves. The company’s website showed they still made the kind that worked on calcium deposits, but all the calcium fighting bottles of “The Works” I found on-line were very expensive. Then “The Works” appeared in the stores again, but only as a regular toilet bowl cleaner with no claim to removing calcium deposits, or other hard water stains. I tried a few other products than claimed to work on calcium deposits, but they did nothing, not even removing the ring around the waterline that almost all cleaners removed. The calcium in our water sticks really well and is almost impossible to scrape off, so chemicals are needed to dissolve it or at least soften it enough to scrub off.
While doing research on products that would actually remove calcium deposits, I came across a forum where someone said that Coca-Cola Classic did a good job on calcium deposits. Laurie was skeptical about the claim, but I figured it was worth a try. Neither of us drink Coke or other sodas, so we didn’t have any Coke around the house to try out in the toilet, so I dropped by the store Friday on my way home from work and picked up a 2 liter bottle of Coke Classic — paid a whole $1.50 for it. It took two rounds of pouring Coke in the toilet, letting it set for about 45 minutes, then scrubbing the calcium deposits with a stiff scrub brush, but the Coke actually worked to soften the calcium deposits enough that I could scrub them off the inside of the toilet bowl.
Why it worked, I can’t tell you for sure, but it’s probably the citric acid and bubbly. If you drink coke, I wouldn’t be too concerned, because stomach acid is very strong. If I was bulimic, barfing in the toilet and letting it sit for 45 minutes would probably be more effective than Coke, but since I hate throwing up, the next time the calcium starts building up, I’ll try lemon juice with fizzy water and see how that works.
After a 45 minute soak in Coke, and a bit of really hard scrubbing most of the calcium is gone.
Off Center & Not Even 
Buona Domenica 🙂 KISS
Grazie, Simona!
Thank you for this useful information! Going to keep it in mind…
Thanks, Herman! And it has a 100% cat approval rating by Rosencrantz.
Now with Rosencrantz approval we can be sure that it really works…
Useful but it does make you wonder what it’s doing to our insides!
Wow, very interesting!
Thanks, Maya!
Being from the east coast/south, I wasn’t expecting that problem when I moved to ABQ. I didn’t think of using Coke then (even though I knew it was used to clean auto engines!). Here the water doesn’t have to be treated as heavily, so I had not encountered that kind of buildup. It’s devilish to deal with. Great tip, Tim.
Thanks, Teagan. We have untreated water from our private well, so it’s even worse than you had to deal with.
Have you ever tried a product called CLR, Tim? I think it’s supposed to work on calcium deposits. I use it periodically to clean my coffeemaker. Amazing the Coke worked.
Hi Cathy. CLR is one of the products that didn’t do a thing. It’s a useless, expensive product in my opinion. Coke would probably clean your coffee pot as well, and it’s really cheap.
I’ll try it next time.
I looked closer at the CLR and I don’t think it’s really made to get hard calcium deposits out of toilets.
Heard you can also use it on battery terminals too. Which makes you wonder what it does to our innards!
Maybe Coke cleans your insides?
Just glad I don’t drink it!
Hello Timothy, I usually avoid to use chemical products, when possible. I suggest you to use sodium bicarbonate together with white vinegar. I don’t know how ‘hard’ are your deposits but with mine it works! I use it regularly on sinks, in case of slow drain, in the electrical kettle, etc.
Vinegar dissolves calcium deposits, bicarbonate helps scrubbing.
I hope this will help you 🙂
Big hug from Italy
Thanks, PK Queen. Our water is so hard that vinegar doesn’t really do much either.
Add some mentos to a diet coke and you have a pressure washer along with the cleaning power of coke.
There you go! Thanks, Craig!
We’ve emptied the shelves of our local hardware store trying to find something to clean the deposit on our glass shower doors. Never thought of Coke, even though I have read in the past about how it miraculously cleans deposits on car batteries. Gotta stop at the store tonight and pick up a bottle. Thanks!
Once you get the shower doors and shower clean you can try Clean Shower spray after each shower. We’ve found it works really well at keeping the water deposits off of the bath enclosure.
Thanks, Tim. The guy at home depot said we should use Rain-X. But I tried that on my windshield on the car once and didn’t like it.