400 gallon spa, 2 person with 1 hour soak

Kathy Bailey

New member
Oct 19, 2020
1
Lusby
I have been reading this forum for about 2 months now. I am very happy with the results of my hot tub. I started using the BBB method and am very pleased. I also got the K2005C Taylor test kit which has made me more confident when testing my water.

Just a question, how much Chlorine should I put in per person? I am using 10%. I usually add 4oz after getting out, but it is usually down to 1 to 3. So I add another 3 to 4 ounces depending on the results. Is that sufficient?

Also when testing, sometimes after a few days of not bathing, chlorine is above 10, how do you test ph and get an accurate reading, it is always above 8.

Please direct me to any additional information to read.

Today's numbers:
FC 3
PH: 7.8
TA: 80
CH: 160
CYA: 34
 

jseyfert3

Silver Supporter
Bronze Supporter
TFP Guide
Oct 20, 2017
1,348
Southern WI
Pool Size
15000
Surface
Vinyl
Chlorine
Liquid Chlorine
Welcome to TFP! Based on the contents of your post, you've done a lot of reading here already. (y)

We usually round this up to the nearest multiple of 10, so we'd say that's a CYA level of 40. Reason for this is it's not the most accurate test, and the scale is logarithmic, not linear, and most people don't know how to "eyeball" a logarithmic scale correctly. So overall it's better to just round up to the next multiple of 10.

Also when testing, sometimes after a few days of not bathing, chlorine is above 10, how do you test ph and get an accurate reading, it is always above 8.
You cannot get an accurate pH reading when the chlorine is above 10. Taylor includes enough chlorine neutralizer in the pH test to test up to 10 ppm of FC.

Do you have a salt water chlorine generator (SWCG), or are you manually adding chlorine and taking the chlorine level above 10? For a CYA of 40, we recommend a FC of 5-7 ppm, with a maximum (SLAM) level of 16 ppm. It's safe to get in up to the SLAM level, but like you mentioned you can't measure pH if the FC is that high.

Just a question, how much Chlorine should I put in per person? I am using 10%. I usually add 4oz after getting out, but it is usually down to 1 to 3. So I add another 3 to 4 ounces depending on the results. Is that sufficient?
This depends on your personal usage. Some people shower before use, some don't. Some have lotion or perfume, some don't. The only real way to know how much you should add is to test and track how fast it gets eaten after adding. Generally, I personally try to add enough that the following morning or evening my FC hasn't dropped below the minimum FC level on the FC/CYA chart. The maximum you should add is whatever would cause you to reach the SLAM level. You can calculate this with PoolMath, there's either a phone app or a website.

I would say what you're adding seems sufficient, but I'm curious why the chlorine is above 10 after a few days of not using. Once we figure out why that is we can try and dial in the amount you add after usage.
 
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