Pool Water Chemistry

Pool Water Chemistry, Secrets Revealed

Chlorine kills microorganisms and oxidizes everything else. This happens when your Tri Chlor tablets react with water to form hypochlorous acid. This IS your most wanted outcome. Sounds simple, right?

Don't Pee in the Pool (forgive me for being blunt)

Hypochlorous acid from your chlorine loves ammonia. The ammonia in urine (and sweat) naturally bonds with the free chlorine in your water, creating a compound called chloramine

The creation of chloramines is the result of your chlorine being destroyed by ammonia. The chloramine has zero sanitizing ability and smells bad too. Chloramines can only be removed by super chlorinating the water. This is why you shock after heavy bather usage.

And you thought peeing in the pool was unsanitary for it's own sake. It is pool water chemistry gone bad. Urine destroys the sanitizing effect of your chlorine.

Why pH Can Bankrupt You

The secret? Low pH gives you more free chlorine. You use less chlorine tablets and get more free chlorine in your pool water.

High pH allows less free chlorine. You use more and more chlorine and get less sanitation.

This one simple fact of pool water chemistry can save you hundreds of dollars a year.

High pH, greater than 8, causes dissolved minerals and metals to precipitate, makes the water cloudy. These solids also build as scale in heaters, filters and pipes.

Low pH, below 7.0, means the water is acidic. This causes eye irritation. Below 6.5 pH, the water is damaging to metals in the pool or filter system. Very low pH will damage your automatic pool cleaner and every other pool part..

pH Affects Chlorine !! pH is kryptonite to Chlorine

At PH 7.2, about 60% of chlorine exists as the most wanted hypochlorous acid. At pH 8.5, only 10% exists as our most wanted acid. At pH 7.0, dissolved chlorine will be 75% our desirable acid. Chlorine is almost 8 times more effective at pH 7, than at high pH 8.5


Now the unrecognized problems.

Chlorine Affects pH! It’s true. Tri Chlor is very low pH, about 2.9. VERY acidic and should not be placed in the skimmer basket where the acid may gravitate to your pump .

To offset the acidity, add a quarter pound of soda ash or borax for every pound of Tri Chlor or use a high pH shock.

Chlorine Shock Affects PH

Liquid chlorine, such as Clorox, Calcium Hypochlorite and Lithium shock are all very high pH. Use these shocks if pH is low. DO NOT use these shocks if the pH is already high. The water may get cloudy if the pH is too high.

Calcium shock will cloud the water in the best of conditions. Avoid using calcium shock when your pool is suffering from a high pH level.

Liquid has pH 13, can be neutralized with muriatic acid at the rate 1 quart acid for 2 gallons liquid shock.DO NOT MIX ACID AND LIQUID SHOCK TOGETHER!

Lithium shock has pH 10.7. Calcium shock has pH 11.8 Both pH’s may be offset with 4 ounces muriatic acid per pound of shock.

For high pH conditions, use Dichlor shock. It is almost PH neutral, dissolves quickly and has a long shelf life. Dichlor shock is stabilized. It will increase the cyanuric acid (CYA). Only use if pH is high and stabilizer is low.

Raise or maintain your pH with chlorine pool shock.

Who Knew the type shock you use, may BE the problem?

BEST PH for maximum chlorine efficiency is 7.2. The one factor that upsets pool water chemistry is the PH of the chlorine itself. Throw Calcium shock into an algae bloom and the pH increases lowering the amount of free chlorine available to kill and oxidize the algae. As the PH climbs, the calcium stops dissolving causing the water to be cloudier still.

Basic Pool water chemistry will save you time.

When adjusting pH, you must account for the chlorine shocks addition to the alkalinity. When fighting algae, keep the PH low to maximize the power of the chlorine.


CYA or stabilizer slows the sanitizing and oxidizing ability of the chlorine. As a rule of thumb, maintain 1 ppm free chlorine for every 10 ppm of CYA/stabilizer/cyanuric acid. EG: Cyanuric acid 80 ppm, maintain 8 ppm free chlorine.

If you have algae growing despite what is considered to be adequate chlorine then check the stabilizer level and adjust free chlorine accordingly.

Sunlight will burn off 50% of your chlorine every half hour if no CYA is present, so be sure to maintain CYA minimums.

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