Swimming Pool Chemicals Part One-Just What Am I Putting in My Pool?
Posted: Tuesday, November 28, 2006
by Rob Dr Duck Coxworth
Webfoot Leisure.com
As owner and operator of a retail site selling pools and
everything to do with pools and spas I am constantly amazed by the need for
information on many of the basic products used by pool owners.
Since chemicals are a universal, this and subsequent articles will
hopefully give pool owners a better idea of what they’re putting in their pools
and how it will perform.
Chlorine is still King of Sanitizers for swimming
pools. Chlorine and its relative Bromine are members of the halogen
family of chemical elements. Halogens share the characteristic of
being powerful oxidizers, which makes them ideal for swimming pools and
spas. The oxidizing property breaks apart chemical contaminants
from swimmers and the environment making the pool unattractive for infestation
by algae and bacteria. Having said this swimming pool chlorine is
available in a number of different forms each possessing unique
properties. This article will discuss each popular type.
Bleach (sodium hypochlorite) is a liquid form of
chlorine identical to the bleach used for laundry but in a more concentrated
form. Laundry bleach usually provides 4-5 percent available
chlorine while pool bleach is 10 percent or a little more. Bleach
isn’t a very good pool product compared to other types of chlorine available
today. It’s expensive; chorine in other forms delivers 56 to 90
percent available chlorine compared to 10 percent for bleach.
Bleach also has a pH of over 13. This will tend to raise the
pool pH unless pH reducer is added regularly. Bleach is
unstabilized and easily broken down by the UV rays in sunlight.
Once added to the pool it will be gone in about 2 hours.
Bleach may also add dissolved solids that can make pool water cloudy and
unattractive. Given the drawbacks and availability of better
sources of chlorine bleach shouldn’t be an option for use in a swimming
pool.
Calcium Hypochlorite (Cal Hypo) is usually sold in
granular form although tablets are available, typically for use in septic
systems. Cal Hypo is most commonly found in 1 lb. bags sold as pool
shock. Cal Hypo provides a healthy 65 percent available chlorine
but as it is unstabilized sunlight quickly burns it out. If used as
a regular source of chlorine, stabilizer (cyanuric acid) is usually added to the
pool to keep the Cal Hypo from disappearing so quickly. Cal Hypo
makes an effective shocking agent because it does its job and quickly
disappears. There are several drawbacks to Calcium
Hypochlorite. It is the most powerful oxidizer (Class II) available
for pool owners and the most dangerous to store and handle. It can
react explosively when mistakenly mixed with other chlorine products.
It must also be pre-dissolved before use to avoid bleaching out vinyl
liners.
Sodium Dichlor (Dichlor) is always sold as a granular
product and provides 56 percent available chlorine. Typically more
expensive than other forms it doesn’t lend itself well to automatic feeders and
provides a little less bang for the buck in available chlorine. On
the plus side it is a Class 1 oxidizer and somewhat less dangerous to handle
than other forms of chlorine especially bleach and Cal Hypo. It
also makes an excellent shocking agent as it dissolves in water quite
well. Dichlor has cyanuric acid added during production to
stabilize the material so it stays around up to 6 hours in direct sunlight.
Sodium Trichlor (Trichlor) is the most widely used
form of chlorine for swimming pools. Almost always sold in the form
of tablets or sticks Trichlor provides 90 percent available chlorine.
This is the highest percentage available which makes this type of
chlorine the most cost effective. One 3 inch Trichlor tablet
provides nearly seven times as much chlorine as a 4 gallon case of bleach.
The formed product is ideal for automatic feeders and because it is also
stabilized Trichlor will stay around for a while. Like its cousin
Dichlor, Trichlor will not affect pH nearly as much as other products.
Trichlor is also ideal for feeders because it requires flowing water to
dissolve.
Each of these types of chlorine, except bleach, has its place
in keeping pools clean and sanitary. Knowing the characteristics of
each will help save money, time and effort caring for a swimming pool.
Rob "Dr. Duck" Coxworth is the driving force behind http://www.webfoot leisure.com/, an
on-line retailer of swimming pools, supplies,equipment and accessories. Rob has
spent many years in the pool industry in a variety of roles; CEO, manufacturers
rep, consultant, National Sales Manager and part time pool float. Dr. Duck likes
to write about pool issues and share the information he's gained from working
with pool industry firms over the years.
I wonder if Dr. Duck is being disingenuous, or is misinformed. Trichlor contains cyanuric acid, and has a VERY low pH. prolonged use of trichlor will always result in significant pH drops, requiring pH raising chemicals to keep the pH at an acceptable level. There are many, many successful pool owners that use essentially nothing other than grocery store bleach, borax, and baking soda to maintain a crystal clear pool all season long. The claim that bleach is not an acceptable pool sanitizer is simply false, and bleach (when not purchased from a pool store) is easily the most cost-effective pool sanitizer. And this doesn't even address the dramatic overstabilization that occurs when using a lot of trichlor. in effect, the continuous addition of cyanuric acid increases the chlorine demand of the pool throughout the season, resulting in even greater increases in cost. the myth that bleach can't be used is perpetuated by pool stores that want you to purchase more expensive forms of chlorine.I never attempt to change the mind of bleach enthusiasts. You're convinced and that's all there is to it. If your pool works well on the blend of chemicals you use more power to you. Having said that, you would have a hard time convincing the working pool chemists and manufacturers that your prescription is better for the majority of pools than the more widespread products currently available. I've been in the pool chemical world long enough to know that water chemistry can be quite capricious and variable. Translating success with a particular sanitation method to success with all or even most pools is a tall order, one that no one has yet filled. I'd be much more willing to argue tha merits of salt water chlorination than bleach.Despite the argument to the contrary, what Dave S. has posted is 100% correct. Sanitizing with bleach is by far the most economical - that is if liquid chlorine is not the better deal in your area. You do need to add a small amount of cyanuric acid to stabilize the chlorine so that it doesn't get burned off in the sun, but that's a small issue. The article glossed over this part. It also glosses over the fact that long-term use of trichlor will OVERstabilize your chlorine, since you add stabilizer every time you add trichlor. When you overstabilize, the chlorine is rendered ineffective since it is sequestered by the stabilizer. This stabilizer (cyanuric acid) doesn't go away quickly. Once you add it, it stays. The only way to get rid of it is to drain water from your pool and refill.
Very helpful. Thank you for the info.
My pool has turned green as I opened it very late. I am planing to drain the pool, and wash the walls with Clorox. But after reading this useful article I like to know if someone could guide me what I should use to clean the walls with? I don't want to acid wash. Thank You SamDear Sam, I would wash the walls with a solution containing algaecide first then a clorox wash. This will ensure the algae is dead and the clorox will help dispose of the residue. Good luck iwth it. Rob "Dr,Duck" Coxworth
I have a 16' x 48" above ground pool can someone tell me how muchchlorine tab to put in my pool. just don't know what to do