Pool professionals know the price of their chemicals. Ask a service company owner what they're paying for liquid chlorine, and they'll likely have an answer ready. The same goes for trichlor tablets, cal-hypo shock and dichlor.

But the price on the invoice doesn't tell the whole story.

The reason is simple: Not all chlorine products contain the same amount of available chlorine. A gallon of liquid chlorine, a pound of trichlor and a pound of cal-hypo may all cost different amounts, but they also deliver different amounts of sanitizing power.

To make a true apples-to-apples comparison, the cost must be adjusted based on available chlorine.

For this article, Service Industry News used representative contractor pricing gathered from 2026 survey responses, contractor reports and market price surveys. The figures are intended as examples and will vary by region, supplier, and purchase volume.

Representative Prices Used

• Liquid chlorine (12.5% sodium hypochlorite): $5.25 per gallon

• Trichlor tablets (90% available chlorine): $155 per 50-pound bucket

• Cal-hypo shock (68% available chlorine): $190 per 100-pound bucket

• Dichlor granular chlorine (56% available chlorine): $250 per 50-pound bucket At first glance, trichlor appears to be the bargain. A 50-pound bucket costing $155 works out to just $3.10 per pound.

However, that calculation assumes all 50 pounds are chlorine. They aren't.

Trichlor contains approximately 90% available chlorine, meaning a 50-pound bucket contains about 45 pounds of available chlorine. When the cost is divided by the actual available chlorine content, the price rises to $3.44 per pound of available chlorine.

The same principle applies to every sanitizer.

A 100-pound bucket of 68% cal-hypo contains about 68 pounds of available chlorine. At a representative price of $190, the actual cost works out to approximately $2.79 per pound of available chlorine.

A 50-pound bucket of dichlor contains about 28 pounds of available chlorine. At $250 per bucket, the true cost is approximately $8.93 per pound of available chlorine.

Liquid chlorine is sold by volume rather than weight. For purposes of this comparison, a gallon of 12.5% sodium hypochlorite is treated as containing approximately one pound of available chlorine. At $5.25 per gallon, the cost is roughly $5.25 per pound of available chlorine.

Using those assumptions, the comparison looks like the table above.: Another way to compare sanitizers is to focus on the result pool professionals are actually trying to achieve: increasing free chlorine in the water.

How We Calculated the Numbers Using the industry rule of thumb that one pound of available chlorine raises free chlorine approximately 10 ppm in 10,000 gallons:

• Liquid chlorine (12.5%): 1 gallon ≈ 1 pound available chlorine.

• Trichlor (90%): 1.00 ÷ 0.90 = 1.11 pounds.

• Cal-hypo (68%): 1.00 ÷ 0.68 = 1.47 pounds.

• Dichlor (56%): 1.00 ÷ 0.56 = 1.79 pounds. Not surprisingly, the results closely mirror the available-chlorine calculations because a 10 ppm increase in a 10,000-gallon pool requires roughly one pound of available chlorine. The two methods simply express the same concept in different ways.

Viewed this way, the differences between sanitizers become easier to see. A technician may think of trichlor as costing $3.10 per pound because that's what the bucket price suggests. In reality, that pound of product delivers less than a pound of available chlorine. The true cost of achieving the desired increase in free chlorine is closer to $3.44.

Of course, chlorine cost is only one consideration.

Liquid chlorine adds neither calcium nor cyanuric acid. Trichlor and dichlor contribute stabilizer. Cal-hypo contributes calcium hardness. Depending on the pool, those side effects may be either beneficial or undesirable.

Regional pricing can also dramatically change the equation. Florida service companies, for example, often report liquid chlorine prices that are far lower than those found in much of the rest of the country. In those markets, liquid chlorine can become one of the least expensive chlorine sources available.

Still, these calculations highlight an important point. The price printed on a bucket, bag, or invoice isn't necessarily the price you're paying for chlorine. Whether measured by available chlorine or by the cost to raise free chlorine in a pool, understanding the economics of a sanitizer requires looking beyond the package price.

After all, customers don't buy gallons, buckets, or bags. They buy clean, sanitized water.