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- USA
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Ships within 48 hours ยท Estimated delivery Jul 5 - Jul 10
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Description
Pool Calcium Increaser, 4-Lbs.HTH(TM) calcium hardness increaser, 4 lbs., is used to raise the calcium hardness of swimming pool water. Low calcium hardness may cause the pool water to be corrosive, resulting in damage to pool surfaces and equipment. Plaster finish pools may be etched or stained if the calcium hardness of the pool water is not properly adjusted. The calcium hardness of chlorinated pool water should be maintained in the range of 200 500 ppm.
HTH(TM) calcium hardness increaser, 4 lbs., is used to raise the calcium hardness of swimming pool water. Low calcium hardness may cause the pool water to be corrosive, resulting in damage to pool surfaces and equipment. Plaster finish pools may be etched or stained if the calcium hardness of the pool water is not properly adjusted. The calcium hardness of chlorinated pool water should be maintained in the range of 200-500 ppm.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
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Based on 2194 reviews
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Product Reviews
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4
Great watch; but why the triangle screws?
Color: Black/Digital Gray/Silver-Tone
I have been using these watches for many years with very good luck, and would normally give them 5 stars. They are comfortable, waterproof, durable, and have an alarm and a countdown timer. (The waterproof and countdown timer - that can be set to repeat - make them good for sailboat racing, and these are much cheaper than sailing watches. )
But at some point before the watch breaks, the battery will die. It is not hard to replace the battery. Except now the watch comes with triangle head screws holding the back on, rather than the regular phillips head screws they used to have. Why? Is it that important to keep people from opening up their watch? Making things harder to fix is a step in the wrong direction. Knocking off one star for that.
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Reviewed in the United States on August 28, 2025
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5
Still the champ.
Color: Black/Negative Digital/Gray, Color: Black/Negative Digital/Gray
I absolutely LOVE my Casio GBA800 that I have bully bars on, so she's quite huge. Analog with Bluetooth, pretty cool. If I ever remember to use such things. I have a phone and laptop on me usually, why do I need to play with my watch? I want to tell time, that's it.
Comes along a good sale for an Ironman, and I used to be a complete fanatic for only Ironman for a real person's needs. Why not, I've been fighting the Casio all day with my coat cuff, let's get something a bit slimmer for when it's coat season. See if they're still great. Yup! Sure is.
It's been probably 25 years ago last time I wore this style of Timex, and can you believe the button setup and beeps are all still the same as way back when! And somehow, my subconscious remembers the button presses. Wild.
This thing is light as a feather, and I got the inverse LCD for fun, which is cool as all get out, but takes some getting used to. The Indiglo sure looks awesome, though, and she's like Knight Rider down there. Stealth. The display is big, and easy even for my old eyes, the band is supremely comfortable, and there's a strap catch that actually works correctly! With no Bluetooth, battery life should be outstanding - always used to be. Back when watch batteries were like $12 each. There goes my allowance! Lol.
I'm very impressed by this timepiece. I really didn't mean to order order it, but, oh well. I love it as much as my Casio. Affordable tough watches rock!
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Reviewed in the United States on January 21, 2025
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5
The colour is cool
Color: Black/Digital Black/Black
Cool stuff
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Reviewed in the United States on May 20, 2026
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5
This Timex Ironman lives up to its name
Color: Black/Digital Gray/Black
Timex Ironman watches have been with me for a decade. This particular one I just ordered as a backup for the same one that I have had for seven years (and still works perfectly). I don't know why I ordered a backup except that I love it so much that I couldn't fathom the idea that Timex might discontinue this model. Why do I love it so much? Because it is functional in many ways. Aside from its durability, reliability and the fact that it fits on my wrist so comfortably, it is easy to read and extremely useful for tasks that need countdown alarms as well as regular timers (it has three which you can set). Since I gave up "fashionable" watches years ago in favor of practical, easy to read, multifunctional devises I found this Timex the best of all the other brands that I have tried in this category. Years ago, President Bill Clinton, who jogged regularly, was heavily chastised for wearing a very functional Timex Ironman watch in the Oval Office instead of what the professional politicians considered appropriate for a President. It was then that I realized how important it was for a person to wear a watch that they loved, and that was functional for them. At that point in time I had many other watches that I didn't jettison until later when I realized that I need only wear the watch that I loved and was useful to me. I still have another watch that I saved for "appropriate" times out but have only worn it once. The rest of the time my Timex Ironman stays on my wrist wherever I go.
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Reviewed in the United States on September 13, 2025
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5
A very comfy, pleasant casual sports watch- especially good for training
Color: Black/Digital Gray/Silver-Tone, Color: Black/Digital Gray/Silver-Tone
The Ironman series of watches has been around for about 40 years now, and with good reason. The current iteration doesn't disappoint. It's light weight, easy-to-read, has a good backlight, offers simple operation, great buttons, a decently loud chime, and is a feature rich watch. I purchased this one on a lark; it was sold as "used- very good" from an Amazon warehouse for $20. The Timex packaging/ box was damaged, but the watch itself was new, wrapped and seemed unused. Since I do not wear an item's packaging, I always look for such items when shopping on Amazon, as it can save quite a bit. In this case it was $12 less expensive, or about 1/3 less costly.
I have owned a digital watch for over 40 years; from left to right in the photo- my 1980 Seiko (owned since new), my daily Casio, which has solar and atomic clock radio signal time setting, and the Ironman for you to compare size. Owning a number of Casio digital watches, I was pleasantly surprised by the comfort and ease of use of this Timex Ironman. The Ironman does feel somewhat more "plasticky" that some Casio watches I have, which may influence some buyers. But once you get past that feel, if you like the look of the watch, it's a great offering, especially at a $20 price point. The on the Ironman, a chronograph, a countdown timer, a second time zone, three alarms, 30 lap records, occasion reminders , and a perpetual calendar make it comparable, or better than many of the similarly priced Casio offerings. The Ironman does not feel quite as substantial as some of the lower cost G-Shock offerings I have tried, but is at least as comfy on my 7 1/2 inch wrist. Water resistance seems fine at 100 meters, and the recessed plastic crystal should avoid most scratches. The features should be very useful for those who do not want to wear a smartwatch for training. I hope this review has been helpful.
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Reviewed in the United States on May 6, 2023
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