Pool Chlorine Brands – What’s the Difference?

drpool-shock-3Pool chlorine – one of my favorite topics! Hello again, I’m Dr. Pool, resident chemist at In The Swim.

Why would a chemist work for a pool supply retailer? To create & test our own chemical formulations, in a state of the art compounding facility.

Is all pool chlorine the same? The short answer is NO ~ Trichlor tablets may look the same, but they differ in “materials and workmanship”.

Chlorine Materials

Chemical labeling and MSDS sheets provide a look into the ingredients used in chlorine tablets and pool shock, but manufacturers are allowed “proprietary” license, to not list trade secret ingredients.

Trichlor tablets can contain additives to control algae or improve water clarity. In such cases, a lower percentage of available chlorine will tip you off to the use of fillers or additives.

Cheaper binders can gum up chlorinators and cloud pool water. Raw materials can contain impurities or be cut with low grade fillers in cheap chlorine.

Chlorine Workmanship

How chlorine is made does make a difference in the level of impurities, and in how the chlorine is delivered. Cheaper tableting equipment can produce a crumbly tablet that dissolves too rapidly.

pool chlorine types, pool chlorine tablets or trichlor tabsA chlorine product’s solubility, hardness and bulk density affects the release rate and is dependent upon the heat and pressure used during tablet formation, as well as the quality and purity of ingredients.

It takes a lot of pressure and heat, and precise cooling to create a well-made chlorine tablet, and do it without harm to the environment. Less sophisticated tableting facilities produce an inferior product and discharge excessive byproducts into air and water.

Country of Origin

In recent years, chemical manufacturers in the U.S. have petitioned the International Trade Commission for protection and sanctions against imported isocyanurate products being dumped on the U.S. market.

dept-of-commerce-logoLate last year, the Dept of Commerce ruled that imported Chinese chlorine was found to be heavily subsidized by the Chinese government, and was unfair to domestic manufacturers.

The effects have already caused one major US chlorine manufacturer to stop producing pool chlorine – Chemtura. Tariffs will increase for Chinese chlorine, which likely will force cost cutting measures to maintain profit on their investments.

Differences in Chlorine

In a nutshell, there are significant differences in the quality of chlorine tablets and pool shock. This results in tablets that dissolve too rapidly and leave a gummy residue, and granular products that separate too slowly, and leave behind a cloudy residue.

There are many ways to make a cheap chlorine product, so stick with a major brand; and avoid private label brands and sales on “Generic” pool chlorine from big box retailers, home stores or discount clubs, which are domestically packaged with imported chlorine.intheswim-chlorine-tablets

No matter what type of chlorine you use – Trichlor, Dichlor or Cal Hypo – look for a respected brand of domestic pool chlorine, and steer clear of chlorine products of dubious origin or of poor materials and workmanship.

Dr. Pool

Dr. Pool



Pool Chlorine Brands – What’s the Difference? — 9 Comments

  1. Good evening
    I’m 19 weeks pregnant with my first baby and everything is going swimmingly. I’m looking to go scuba diving next week with my husband in Fiji. We usually go to 20 metres deep and I was wondering how pressure would effect the baby and if it’s safe to scuba dive while pregnant? How deep can I dive?
    Thank you
    Kind regards

    • Hi Jacqueline, although I am no expert in scuba or the effects on unborn children, there are some reports of problems with hyperbaric oxygen, or oxygen under pressure. Maybe not so much from pressure of being underwater, but from breathing canned air? I found this: “A range of developmental abnormalities have been associated with hyperbaric exposure. These include low birth weights among the offspring of diving mothers 14,15,26; fetal abortion 28; bubbles in the amniotic fluid 13,25; premature delivery 14; abnormal skull development 11,15,16; malformed limbs 11,15,16; abnormal development of the heart 16,20; changes in the fetal circulation 2; limb weakness associated with decompression sickness 21; and blindness 14.” So, although I am not a doctor, I would recommend that you stay near the surface and use a snorkel 🙂

  2. I am looking for a chlorine product that wont raise my cya, I use a product now called GLB. Is this a good product?

    • HI – GLB is a good brand of chlorine products. Stabilized chlorine tablets are those known as Trichlor, and also Dichlor granular shock. Non-stabilized (without CYA) – that’s any of the hypos – cal hypo, lithium hypo (both granular) or liquid sodium hypo. You could use 5 gallon liquid drums, with the Pool Pal chlorinator, or use Cal Hypo tablets, with a Cal Hypo tablet feeder (do not use a Trichlor feeder or floater). Both systems are a bit pricey however, and the tablets are also expensive (cal Hypo tabs). You could also switch to bromine, which is not stabilized with cya. Or, you could just use Trichlor and use BioActive cya reducer as needed, or replace 1/4 of the pool water every season, to lower cya.

  3. Stablizer question – my salt chlorinator died and I have been using TriChlor tabs. While doing this I have also had to ADD CYA, but everyone is saying that TriChor has stablizer, and using TABS has driven their CYA over the limit?

    I am confused about this – I use ~ 2 3″ tabs a week, 19K gallons. But my CYA reads zero if I do not add any? What is up with that?

    • Hi, Trichlor tablets or sticks do contain a small amount of stabilizer, but it would take months or years for the level from tablets alone to build up to a good cya level, longer for pools that get regular rain, or have small leaks, backwash frequently, or lower the water for winterization, all which dilute the cya concentration. That is why most people will start with adding 20 ppm or so, of cyanuric acid (2 lbs per 10,000 gals), to give an initial boost to untreated water. After that, for many pools, just using tablets will raise the level to 30 ppm or so, by the end of the summer.

    • There are several types of chlorine, for granular or powdered chlorine there is Calcium hypochlorite and lithium hypochlorite, with calcium being twice as strong as Lithium, but half as easy to dissolve (not as fine). There are Trichlor tablets and Cal Hypo tablets, Trichlor is stabilized and slow dissolve, Cal Hypo is not stabilized and fast dissolving. So, yes you are correct that the main differences between chlorine are dissolution rate and potency, but also other factors like if it is stabilized with cyanuric acid (or not), or if the pH level is high, low or neutral. And know this – all chlorine types are incompatible and will explode or ignite if they contact each other, even just a grain or granule.

  4. Pingback: In The Swim: Pool Chlorine Brands – What’s the Difference? | DesRochers Backyard Pools

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