Best Chlorine Types for your Pool

Liquid Chlorine or Bleach is the tried and true standard chemical of choice for most pool service professionals. It is easy to use and relatively inexpensive and it has the least side effects of any of the chlorine you can choose from. It is usually sold in 12.5% active chlorine per gallon with Bleach coming in at about half that strength at 6.5%. It will raise the pH slightly, but it does not contain any Stabilizer or Conditioner making it ideal for all pool types. This means that when you add a gallon of liquid chlorine and your Conditioner level (CYA) is 50 ppm it will stay at 50 ppm even if you add 20 gallons of liquid chlorine.

Pros:

Fastest acting of all chlorine types

Will not raise your CYA level

Safe for all pool types

Easy to use

Cons:

Breaks down by the Sun’s UV Rays so your pool needs a CYA level of 30-50 ppm

Short shelf life so rotate stock or buy fresh chlorine when needed

The gallons can be heavy compared to a bag of shock

Is seen as weaker than shock based on the low percentage of chlorine but is stronger

Cal Hypo is very popular and there are a number of reasons why it is widely used in the industry. It is easy to carry and comes in different strengths 60-75% active chlorine. One of the major side effects is that it contains calcium, so over time it will raise your pool’s calcium hardness. Not an issue if you live in an area with soft water but I caution the use in areas with hard water. It also has a high pH of around 12 so it will raise the pH in a pool if you use a significant amount each week. It can also make the pool cloudy if you pour a bag directly in. A very powerful form of shock.

Pros:

Strong and easy to use

Does not contain Conditioner so it will not raise the pool’s CYA levels

Safe for all pool surface types but use caution with a vinyl liner

Cons:

Raises Calcium Harness in a pool

Raises the pH in a pool

Clouds up the pool water

Dichlor is a very popular form of chlorine and the granular form makes it very easy to measure and use in a pool. It is pH neutral which means it will not raise or lower the pool pH in any significant way. It does contain Conditioner, about 45%-50% by weight. So, if you add 10 lbs. of Dichlor to a pool you are also adding about 5 lbs. of Conditioner. Over time this will increase the pool’s CYA levels. A little Dichlor goes a long way making this an ideal chemical to carry on your truck if you service pools. Just don’t overuse it because of the high amount of Conditioner in the product. It is usually about 62% active chlorine by weight.

Pros:

Easy to use and powerful

pH neutral

Safe for all surface types

Long the shelf life of 2-3 years

Cons:

Adds Conditioner to the pool

Tri-Chlor or Trichloroisocyanuric Acid comes in three forms. The familiar 3” tablets that slowly dissolve in your pool, a very fine powder shock and a granular form. About 50% of the Tri-Chlor by weight is Conditioner. So, a 50 lbs. bucket of tablets is about 25 lbs. of Conditioner. If you overuse tablets your pool’s CYA level can go up rapidly. Trichlor tablets are usually 95% to 99% active chlorine. Tri-Chlor tablets have a very low pH of 2-3 so they will lower the pH in your pool. The tablets contain acid in the for of Cyanuric Acid so if one falls into the pool it is likely to stain the surface by burning it.

The powder form of Tri-Chlor shock is a good mix of both power and less Conditioner per pound. It is fast acting but has a strong chemical smell so use caution when using it. It is less pure than the tablet form and is usually 65%-70% active chlorine.  I use it on my route and find it to be effective in shocking a pool.

Tri-Chlor granular is very powerful stuff. It is basically the Tri-Chlor Tablet grounded up in granular form and is 99% active chlorine. Use with extreme caution as the Conditioner in the granular can stain the plaster. The CYA in the tablet is basically acid and if you let it pile up on the pool surface it will stain the plaster as if you dropped a 3” Tablet into the pool. Never add this to the skimmer and if you do use it for Black or Mustard algae make sure it is evenly dispersed on the pool surface. Not for use in Vinyl, Fiberglass or color plaster pools.

Pros:

Very strong and slow dissolving in tablet form so it releases chlorine all week long

Easy to use and affordable

Cons:

Can stain the pool surface

Contains 50% CYA by weight