Don Vandervort, Head Homeboy, has written more than 30 DIY home improvement books, been a segment host on HGTV, served as MSN.com's home improvement expert and written countless magazine articles.
Swimming Pool Sanitization: Chlorine Shock Treatments
A chlorinated pool typically contains two types of chlorine. Free available chlorine (FAC) has maintained its pure chemical composition and is standing at the ready to clean up contaminants. Combined available chlorine (CAC), also called chloramine, has already done its work and now is impure because it has combined with ammonias and other contaminants in the water. (These contaminants, for the most part, come from urine, sweat, and saliva.)
When a pool smells like it has too much chlorine and the water burns your eyes, you are actually smelling the contaminated CAC rather than the pure FAC. We often think that the odor and irritation are the result of too much chlorine, but they actually indicate that there is not enough FAC in the water.
The solution is to “shock” the water by adding a large dose of chlorine, a process called super-chlorinization. This megadose breaks down the CAC and re-establishes a healthy level of FAC.
Administer a chlorine shock at night, after people have finished swimming, so the water can have time to recover. At the very least, give it an hour or so before allowing people into the pool, and make sure the pump and filter are operating. Purchase an amount of shocker suitable for your size pool. One form is a powder that you scatter over the water at various locations in the pool. Use a free-chlorine test kit to make sure you have achieved free chlorinization. If the treatment did not work sufficiently, repeat it.
If a pool is heavily used, you may need to shock it on a weekly basis. Otherwise, administer a shock when the pool smells bad or when a test kit reveals the need. If you want to lessen your maintenance time by partially automating the task, consider installing a salt chlorine generator (see Swimming Pool Sanitization: Salt Chlorine Generators).
