“Break-point” or superchlorination.
The need for “break-point” or super chlorination occurs when there is a build-up of chloramines or combined chlorine in the pool water. Chloramines are a combination of chlorine and usually nitrogen. When the chloramine situation becomes “bad” it is because hydrogen has combined with the nitrogen to form ammonia.

Chloramines can and do contribute to algae blooms and cloudy water. The more chloramines present, the more dull the water becomes. The pool doesn’t sparkle as it should. The added nitrogen becomes food for algae. The water smells like there’s too much chlorine, but the actual FAC (the chlorine that is killing bacteria) is low or maybe even zero!

Here’s an example: The total amount of chlorine in the pool is 2.0 ppm but the FAC is 1.0 ppm. That means there is 1.0 ppm of chloramines. Chloramines must be completely destroyed or they will produce MORE chloramines and the situation will worsen.

When treating chloramines, it’s an “all or nothing” proposition. In cases of very high chloramines, it is often a good idea to use a mono-persulfate shock (MPS) which will break up most if not all of these nitrogen bonds without adding more chlorine to the pool. This is good to do in cases where the FAC is over 1.0 ppm.

If your pool has less than 1.0 ppm FAC and lots of chloramines, follow that MPS shock with a solid chlorine shock of Cal-hypo or lithium shock. To reach break point, 10 times the amount of chloramines present must be reached to destroy the chloramines.

In the example above, you would need to reach 10 ppm of FAC to reach break-point!

Typical doses: Double or Triple the amount of regular shocking.

Chlorine Demand.
These are the typical symptoms if your pool has a chlorine demand problem: an inability to hold or maintain a normal Free Chlorine residual (1.5 ppm or higher) over several days, cloudy or hazy water, visible algae that just won’t clear up.

Behind the scenes, there are most likely chloramines that are combining and re-combining due to inadequate shock treatments. When “break-point” is not reached, chloramines recombine with a vengeance & become more difficult to destroy.

Treating a chlorine demand is similar to break-point chlorination except that the stakes are higher.

Treatment must be complete and done at ONE time. It’s like long-jumping the Grand Canyon; you must do it in one jump. You can’t be short!

We often ask a customer who is dealing with a chlorine demand problem, "how much shock have your added?" They respond, "oh, tons! I've added 30 lbs." We ask, "over what length of time?" They respond, "over the last month." Unfortunately, that' s typically not nearly enough. Meeting chlorine demand must be done in ONE SHOT. And no, it's not too much chlorine.

Most people don’t know that their pool has a chlorine demand problem until they have shocked & shocked & shocked and nothing has happened. The water won’t clear. The algae persists. A solid chlorine level is almost impossible to maintain.

Even a clear pool can have a chlorine demand. If the pool can’t hold chlorine, yet the water balance (pH, total alkalinity & calcium hardness) is good and proper, then a chlorine demand exists.

The best way to determine a chlorine demand is to perform a chlorine demand test. The BioGuard® Accu-Demand 30 is one of the most accurate methods for chlorine demand testing. The test takes about one hour. In extreme cases, the test may call for shocking the pool with up to 75 lbs (sometimes more) of shock in a 20,000 gallon pool. Don’t be “shocked”!

Read the complete Chlorine Demand article here.

The good news: once the chlorine demand is met, it is met. The pool will normally stay in great condition for weeks or months on end. But remember, shock your pool weekly or you could be back to a break-point or chlorine demand situation.

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