I took my water to a dealer to have it tested. They said there was plenty of chlorine, but no free chlorine. Their opinion was that adding the high doses of chlorine to super shock the tub was bleaching out the test strips for all the readings and that it would be best to drain and refill the tub. I am now just completing the drain and refill process.
Snowbird: How much dichlor do you use when you super shock your 385? Are your chlorine levels around 0 24 hours after use?
The only time I get a zero reading is when I return from vacation and haven't been dosing it regualrly. In that case I follow the charts in the Taylor kit.
Your strips probably do not measure the different types of chlorine.
Free Chlorine (FC) "...is the workhorse of sanitization, killing germs and oxidizing organics." 2-10 ppm is acceptable and I shoot for 3ppm. The Taylor manual says FC has no odor up to 10-20 ppm.
Combined Chlorine (CC) "...is the reaction of FC with amonia wastes from bathers. CC causes the characteristic "chlorine odor"..." "CC has little sanitizing capability."
Total Chlorine (TC) "...is the sum of the FC and CC residuals..." "TC = FC + CC"
"Breakpoint chlorination is achieved by
superchlorinating (shocking the water with chlorine). Here, the chlorine level is increased dramatically in a short period of time."
"Superchlorinating to the breakpoint has the unique capability to destroy CC. Chemists know that when FC is increased to ten times the measured CC, the level of CC will be reduced to a minimum:
"breaklpoint dosage = 10 X CC""adding
less than the breakpoint dosage can create
more CC!" Remember that CC has no sanitizing value and it smells.
I am no chemist and can not explain this stuff. that is why I am quoting from the Taylor manual that came with the test kit. I follow it and it works. I test once or twice a week and we use the spa 3 out of 7 days. We always make sure we are clean going in and since it is an indoor spa, this isn't too difficult.
I add 1/4 tsp per person after each soak. And maybe 1 tbsp each week (sunday usually) to shock. It varies depending on the test readings and use.
I follow a specific order when testing... 1st TA, then pH, then Chlorine.
Occassionally (monthly?) I check Calcium and CYA.
The Taylor formula for water changes is: 1.3 of the volume in gallons divided by max nbr of daily bathers.
In my case 550 gallons divided by 3 equals 183
I is rare when anyone uses the spa other than my wife and I so... 183 divided by 2 equals 91. I change my water every 91 days.. more or less. This is about right because the water gets a certain feel to it when it needs changed.
My point here is to show you and others that the test strips is a pretty crude way to monitor your water, but if it works for you and you are satisfied, continue using them. I tested the strips against the kit and the differences were very large. So for accuracy and peace of mind, I chose the test kit. It was a real PITA in the beginning but it is no big deal now and takes less than 5 or 10 minutes.
I got my kit from rhtubs.com at a decent price and he has lots of info on his site to help you out.
I am learning myself and there is plenty of help from this board. They helped me alot.