We received an email recently from ‘Michael’ who asked us a question about pool water. He asked,

What does .25/.25, and .5/1, in the free/total column from the Taylor Test Kit represent in a pool log, are these levels safe for swimming. If not what levels from the Taylor Test Kit would be normal. What ORP level is considered to dangerous for swimming. I’m sorry I forgot to mention this is an indoor public pool.

Taylor K 2006 Pool Water Test Kit
Taylor K2006 Pool Water Test Kit

For legal reasons we cannot tell you that your pool water definitely meets all the necessary criteria for getting labeled as ‘safe’, but we cannot assist you with interpreting the data in the log book.

First, we suggest you take a look at an earlier blog posting we did called Free Chlorine, Combined Chlorine, Total Chlorine. The information in that posting will help you to understand the differences between the three basic ‘types’ of chlorine. You will also find some very useful information on Pool Water Testing Blog’s entry entitled Free Chlorine and Combined Chlorine — in a Swimming Pool.

Getting back to your question about the readings in the log book, the entry of “.25 ppm free chlorine & .25 ppm total chlorine” indicates that all of the chlorine in the pool has got converted into chloramines (combined chlorine) and you had no free chlorine, your pool’s main sanitizing agent, available to ‘kill’ any unwanted biological contaminants in the water.

The second entry, “.5 ppm free chlorine & 1.0 ppm total chlorine”, indicates that you had 0.5 ppm free chlorine available in the pool to wipe out any unwanted biological contaminants… and for the record, most pool experts agree that water in a swimming pool ought to contain between 1.0 ppm and 3.0 ppm free chlorine — assuming the pool does not use an alternative sanitizer system (i.e. Baquacil).

By the same token, most pool experts also agree that swimming pool water ought to contain as few chloramines (combined chlorine) as possible. Elevated chloramine levels can contribute to added eye irritation and foul tastes and smells in the water.

What do ORP levels mean?

We freely admit that we do not know a whole lot about ORP and that many people have different ideas as to its usefulness as a means of judging a body of water’s relative safety, but we do know that many water experts believe a properly pH balanced pool (readings between 7.2 and 7.6) with an ORP reading greater than 700 means that the hypochlorous acid (free chlorine) will work effectively as a sanitizing agent.

Michael said he has an indoor pool?

In the case of indoor pools, you will DEFINITELY want to keep combined chlorine counts to minimum because the fumes can build up to noxious levels very quickly. Indoor pools tend to have warmer water temperatures (which increase chlorine off gassing) and less air movement across their surfaces.

Michael said it’s a public pool?

Consult with your local health department and find out what THEY want to see in terms of pool water chemistry because in the end, when they stop by to perform an inspection, their word, and ONLY their word, will determine whether or not your pool stays open that day.

OTO & pH Test Kit for Residential Pools
Total Chlorine & pH Test Kit

FAS-DPD Test Kit
FAS-DPD Test Kit

Complete Service DPD Test Kit
Complete Service DPD Test Kit

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