I am new to TFP. I have been googling pool topics, which led me to this forum. I have read the "pool school" twice. I have a gunite pool that was built 10 years ago. Details are in my signature below. We have had very few problems and no major issues with water over the 10 years, but last summer our chlorine useage was up and it is even higher this summer. I decided to take control of this myself, rather than relying on the pool store, and my first step was to buy the recommended TF-100 test kit. It arrived yesterday and I have done my first tests.
As the topic states, my concern or problem is excessive chlorine use. As indicated in the signature below, I use tri-chlor tablets in a new water dispenser. I use Haviland di-chlor granules and liquid chlorine, as needed, which is every 1-2 days this summer. I do have ProTeam Supreme in the pool and have had for 5-7 years. I understand the CYA issue with tri-chlor and di-chlor, but I like the convenience of the New Water automatic dispenser. Simply stated, I am not at the pool daily to add liquid for the duration of the summer.
Here are my first test results from this morning, after adding 1.5 gallons of liquid and 5 cups of di-chlor granular at dusk last evening.
Free chlorine: 7.0 ppm
Combined chlorine: 1.5 ppm
Total chlorine: 8.5 ppm
Total Alkalinity: 145 ppm
Calcium Hardness: 290 ppm
CYA: 110 ppm
Borate: 30 ppm
Once again, although I have had the pool for ten year and I am fanatical about using the standard OTO/PH test, I am new to this level of detail. I am not a pool chemistry expert, but let me try my first analysis.
Chlorine: The free chlorine content is actually reasonable based on my CYA level. The problem is that is will be gone or very low by this evening. The combined chlorine indicates that I may have some bacteria in the pool since it should be near zero. I know that the sun eats the liquid chlorine during the day and the rest may be fighting some bacteria. The pool is and has been crystal clear, so there is no visible indication of bacteria or algae.
Alkalinity: This is a bit high. My undrstanding is that it can be reduced through aeration of the pool. I do have a fountain and waterfall that run constantly when we are in or around the pool. I have a jetted seating area that runs occasionally. I am not terribly concerned about alkalinity at this time.
Calcium hardness: Appears ok.
CYA: I know that this is high and I expected it since I use tri-chlor and di-chlor. I need to reduce it and I know that it is reduced by draining the pool. Since I live in a northern climate the pool is drained down about 12-18 inches each fall, but this is not enough. I have looked at the CYA calculator and it appears that I need to drain off 50%-65% of the pool and refill. I will do this, but would like to wait until September (when the grandkids are back in school, swimming slows and we stop heating). I fill the pool with our well water, which has a high iron/rust content. I know that adding 50-65% well water is going to cause some rust staining, which creates another issue. Any suggestions on reducing rusty well water would be appreciated.
Borate: Appears to be at the low end of OK. ProTeam Supreme is added at pool opening in the spring.
My summary analysis and plan:
Due to the free chlorine and combined chlorine test I think that I have some bacteria in the pool. The sun and bacteria are eating the chlorine daily causing it to disappear and creating my excessive chlorine useage. I understand that the high CYA adds to this problem. My solution is to shock the pool with liquid. The pool calculator shows that I need to shock with 7-8 gallons of liquid, getting the FC to 39 and then follow the guidelines for shocking. The Ph has been on the low side all summer, but adding this much liquid may increase it to the high normal range. Lastly, I need to drain and replace water to address the high CYA. I would really like to wait until September to do this and get the CYA down to about 50. I know that over time it will increase as long as I use tri-chlor in my New Water dispenser. I accept this as a trade off for the ease of maintaining chlorine and will need to drain water/refill periodically.
Sorry, for the long post, but this is my newbie analysis with the TF-100 results. Please, Please I would like and would welcome expert opinions on my analysis. Am I on track? Do you agree with my assessment. Do you have thoughts, comments, experience to set me straight?