My test results are baffling me.

[JenniferJuniper2]

Okay, so I am new to testing my own water. I have two tests kits, both Taylor brand. One is an OTO kit that tests total chlorine, bromine, and Ph. The other is a K-1001 DPD that tests free chlorine, bromine, and Ph. We tested out water at a pool supply store on Friday and it said our total chlorine was at 10 and the free chlorine was at 10 as well. We tested it with the OTO kit for total chlorine the next day, Saturday, and it was at about 5 ppm. The DPD kit was at about 5ppm as well. We had several people in the pool on Saturday and Sunday. Now it's Monday and the total chlorine reads about 1ppm and the free chlorine is basically completely clear, or zero?! Is this normal? How can a pool go from 10ppm free chlorine on Friday to 0ppm on Monday?

ETA: we did add a little acid in Friday because the Ph was also really high (8) and we brought it down to 7.2. But the Chlorine levels were still high on Saturday, as mentioned above.

 

[bjbarlowe]

I'm still a newbie to the TFP method, but I'd wager a guess that your reading at the pool store was inaccurate, and you were actually at or around 6-7ppm on Friday. Then it would be pretty normal to lose 2ppm per day, especially with a heavy swimmer load. Add chlorine to bring it back to target for your CYA level and I'd keep testing everyday yourself. If you find you're losing more than 3 ppm or so a day, you might need to SLAM the pool because that's one indicator there's something in the water using up the chlorine.

 

[MarianParoo]

Can you get a better FAS-DPD test kit?

 

[welbo]

That actually seems pretty normal to me, especially with use.
Things to consider:
1. Pool store tests are historically very inaccurate
2. OTO and DPD are both only capable of giving you a rough idea of your chlorine levels.
3. The first step everyone here will recommend is buying a good test kit with the FAS-DPD chlorine test, such as the TF-100 or K-2006C.

So, with all that said, what are you intending to do? Because the answers may be different depending on your intentions.
When I first came here, I was really just curious about this TFP method and some of the folks who were very passionate about it turned me off a little on it.
If you are looking to take total control of your pool, save some money and have beautiful water, you have come to the right place. Folks here are pretty smart about that subject.
In other words, whether you want to jump in head first or just see how it works, let us know so we know how to respond.

 

[pooldv]

Agreed, pretty normal. Your pool in perfect condition with nobody swimming in it will use about 2 ppm of chlorine per day and up to 4. Add a bunch of people swimming and that chlorine usage will double or more. It is important to test chlorine before, during and after a big swim day to make sure that the pool is properly sanitized and eliminate risk of person to person disease transmission. To ensure a properly sanitized pool the chlorine level must remain above minimum level for the CYA level on the Chlorine CYA Chart. As soon as it falls below minimum level the pool becomes unsanitary and algae, bacteria and viruses are no longer being killed quickly enough.