Stupid question


Well-known member
Jul 17, 2012
Forest, VA
I went to our neighborhood pool and they post the chlorine level daily. It said 2 in the AM. This is a huge pool with a high bather load. And it looks like that is about normal for a commercial pool (1-3) according to the internet. My question is how the heck with the sun all day is that enough chlorine? My pool loses about 4ppm just to sun. Do they have some special chemicals? Any replies are always appreciated.


Bronze Supporter
LifeTime Supporter
May 8, 2012
Southeast Michigan
I don't know about special chemicals/potions, but that is why they have that recognizable distinctive "chlorine" smell, which we know is not really FC. Probably CC, ammonia, etc. :sick:


Well-known member
May 29, 2019
My guess is that they are constantly adding it. So while that was the test that morning, it doesn't mean they won't be maintaining it throughout the day. I know a guy that used to be a lifeguard, and they had a chlorinator that was constantly feeding chlorine into the pool.


Bronze Supporter
Jul 6, 2017
Kinston, NC
I don't have any experience with commercial pools . They do have different rules which are mandated. One of the problems is their CYA requirements (varies by location) may be low or even none. The following reference refers to a maximum of CYA of 15:

With the constant influx of human products into a public pool and the constant degradation of chlorine by light, there has to be a continuous addition of chlorine to combat that. The main determinant of chlorine demand is likely bather load. Multiple FC checks per day and little to no CYA would allow and FC of 1-3 to be effective IF MAINTAINED. Using the above scenario of CYA of 15, then a 7.5% minimum FC level would be just over 1. That could work. No one would want to manage a residential pool this way. It's too much work.

This Hayward reference Salt Chlorine Pools for Commercial Pools and Spas
gives some insight into demands of a commercial pool. It says that a 50,000 gallon commercial pool may require 120 gallons of 10% liquid chlorine per month. Using pool math that's 8.5 ppm each day and more than twice what a residential pool would use.
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Well-known member
May 27, 2017
Coventry, CT
I used to manage a seasonal pool a long time ago, outside with tons of constant sunlight.

I didn't know much about cyanuric acid but for the fact we didn't use it. The lifeguards check FC and pH every hour (or in reality sometimes every other hour, honestly it was checked very often) shooting for 1-3 ppm and 7.2-7.6 on the pH scale. We chlorinated with variable speed peristaltic pump connected with something like a 55 gallon drum of sodium hypochlorite (liquid bleach). The pump was never turned off, overnight it was turned very low and during the day it was cranked up and adjusted as the lifeguards would check the FC level.

So no special chemicals, just going through tons of liquid bleach.
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