Decreasing Chlorine Formulas

Proper water chemistry is crucial to the safety and health of the public who use public water facilities.  The following information regarding decreasing chlorine should be helpful in maintaining the quality of the water in swimming pools, spas, hot tubs and wading pools in Clark County.  This information is also available for download in Adobe PDF format.   Information on increasing chlorine is also available.

 


Instructions

STEP 1:   Determine the ppm change (decrease):    Current ppm - Desired ppm = ppm change
 

Example: Current ppm (20) - Desired ppm (1.0) = ppm change (19)

STEP  2:   Determine chemical to use to lower the chlorine, plug in ppm change and use the following formula:

1. Sodium Sulfite  (0.2) x (ppm change) x (pool volume / 10,000) = pounds

2. Sodium Thiosulfate (solid) (0.0625) x (ppm change) x (pool volume / 10,000) = pounds
 
3. Sodium thiosulfate (liquid) (1) x (ppm change) x (pool volume / 10,000) = ounces

Example:

200,000 gallon pool has 20 ppm Chlorine. Sodium thiosulfate will be used to decrease the chlorine level to 1.0
Current ppm (20) - Desired ppm (1.0) = 19 ppm change
(0.0625) x (19) x (200,000 / 10,000) = 23.75 pounds sodium thiosulfate

note: " / " means divided by,  x means multiply

How To Shock a Pool

The "smell of chlorine" in a pool is actually the smell of chloramines, the chemical compounds formed when chlorine combines with sweat, oils, urine and other contaminants in the water. Chloramines are not effective in disinfecting the water and cause eye and skin irritation.  Breakpoint Superchlorination or "Pool Shocking" is required to combat the loss of effective chlorine in the water.  Breakpoint Superchlorination is required (on average) every 2-3 weeks for indoor pools and every 7-10 days for outdoor pools.  Heavy bather loads will increase the need for Breakpoint Superchlorination.

Instructions for Breakpoint Superchlorination of your water are available to read online, or you can download and print a copy of the instructions in Adobe PDF format.

Public Water Facility Chemical Log Sheets

Public water facilities are required by 410 IAC-6-2 to keep a record of the pool water chemistry.  Log Sheets for recording this information are available for download in Adobe PDF format.

 

 

Pool Safety Homepage     Pool Accidents and Injuries     Pool Chemistry     Pool Chlorination     Pool Inspections     Pool De-chlorination
Pool Fecal Accidents     Pool Inspections     Pool Regulations     Pool Shocking Instructions     Pool 9600 Rule
 

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