Earlier this Summer we discussed this same topic and we feel quite certain that we will discuss it many more times in the future. Today’s inquiry comes to us from ‘JerseyGuy82560’ who asked,

Sas your answer regarding chlorine not lasting long with the answer being that liquid chlorine without a stablizer was probably the problem. I’m using powdered shock and put 2 pounds in last night at 10 PM. This morning at 6 AM, there was just a trace of chlorine. I don’t want to empty the pool in the middle of the season, so can I use conditioner to make the chlorine last longer? Thank you.

Thank you for your question, JerseyGuy. Many of the powdered (also called granular) shocks on the market have calcium as their base and do not possess stabilizer. For that reason the situation you described where 2 pounds of shock literally vanished overnight makes sense… providing you have not added chlorine stabilizer to the water at some point.

Chlorine Stabilizer, AKA: Cyanuric Acid
Chlorine Stabilizer Powder
AKA: Cyanuric Acid

If you have not added any stabilizer (cyanuric acid) this year, then certainly putting some in now should help you maintain a healthy chlorine residual in your pool water.

If, on the other hand, you have added chlorine stabilizer and still cannot maintain a healthy chlorine level, you either have an abundance of contaminants in the water that require your chlorine’s immediate attention or you may not have enough chlorine stabilizer in the water.

Testing for Chlorine Stabilizer?

Several different test methods for cyanuric acid exist: 1) Wet Kits; 2) Test Strips; 3) Water Testing Meters.

  • Wet Kits for Stabilizer Testing: Test kits of this nature use a chemical reagent that reacts with chlorine stabilizer to create a white substance in test samples which makes the water turbid and difficult to see through. Analysts then measure chlorine stabilizer levels as a function of turbidity.
  • Test Strips for Stabilizer Testing: Test kits of this sort use a small piece of chemically impregnated cloth which changes color in the presence of cyanuric acid. Analysts then measure chlorine stabilizer levels as a function of change in color.

  • Meters for Stabilizer Testing: These devices typically use the same principles as wet kits for determining cyanuric acid levels in pool water samples except the meter interprets turbidity levels instead of analysts taking the measurements. Given the very subjective nature of quantifying turbidity in a sample, meters generally tend to give more accurate and repeatable results.

So, JerseyGuy, if you have clear water at this time and still cannot maintain a proper chlorine residual, first we suggest determining if you have any stabilizer already in your water. Then we suggest bringing the level up to around 30 or 40 parts per million.

We hope this helps!

In the Swim: Cyanuric Acid Test Kit
Cyanuric Acid Test Kit

Pool Check 6 Way Test Strip w/ Cyanuric Acid Test
6 Way Test Strip w/ Cyanuric Acid Test

eXact Micro 7+ Pool Testing Meter
eXact Pool Testing Meter

Spread the Water Testing Word!