LOW CHLORINE PROBLEM
Chlorine is being rapidly lost by some chemical reaction - Please advise.
Pool: Concrete/plaster, 80 000 L = 21 000 US gal., Sand filter new – Hayward S244T, solar heating
Chlorine chemistry: HTH granular 65% Calcium Hypochlorite + 3” HTH pucks in Cl feeder
History of chem. parameters and chemical additions:
May 24 Start up 1pm, 7pm 1400g Cl
May 25, 10am: free Cl 1, pH 7.6, 1-3pm 3.7 L Muratic acid, 4pm 1400g Cl, 8pm 1400g Cl
May 26, 10am: free Cl 0.4, pH 7.0, Stab. 0, 1-3pm 1.75 kg Stab., 7pm 1400g Cl
May 28, 10am: free Cl 0, pH 7.0, 11am 1400g Cl, 10pm 1400g Cl, 10 pm 400g pH-Up
May 29, 8 am 400g pH-Up, 9am 600g Cl, 1pm test: free Cl 0, pH 7.3, Stab. 5
May 30 home test: 7pm free Cl 0.3, 10 pm free Cl 5, 2 hrs after 1400g Cl
May 31, 10am: free Cl 0, pH 7.1, 10:30 pm add 500g pH-Up
Thanks for the question Jaro and the readings
There's a few things that jumped out at me. First is the use of calcium hypo, then muriatic acid, then pH Up.
Calcium hypo is a good source of chlorine, but it has a pH level of 12. Each time you use it the pH will slightly increase. Then you're using muriatic acid to decrease the pH, then pH up to increase it. This is burning a hole in your wallet.
If you're having an issue with the pH jumping around, use liquid chlorine and keep the alkalinity between 80 - 100ppm. This will lock it in place. You can also use unscented bleach for chlorine. It's the same thing as pool chlorine, sodium hypochlorite, only about 1/2 the strength.
On May 25 the pH was 7.6. That was a good reading. If the next pH reading is around 7.4 - 7.8 leave it alone. Only decrease it if it gets above 8.0.
can use baking soda or 20 Mule Team Borax to increase the pH. Baking soda is also used to increase the alkalinity, it's just how you apply it that matters if it hits the pH or alkalinity.
Anything called pH Up or Alkalinity Up is either sodium carbonate or sodium bicarb which is baking soda. Go to your grocery store and get a box of Arm & Hammer for 1/3 the price.
Swimming Pool pH Levels
It seems the reason the chlorine isn't holding is you don't have enough stabilizer, cyanuric acid (CYA). The CYA needs to be between 30 - 50ppm. Use Dichlor and shock the pool. You should be able to get Dichlor chlorine at your local pool store. This will get the CYA into the pool.
Once you get a CYA reading of 30 - 35ppm, stop using Dichlor and go back to liquid chlorine for weekly maintenance. CYA reading should be between 30 - 50ppm. Your'e already using Trichlor pucks which is dosing your pool with CYA so you want to start low and work up from there.
Don't shoot for 50ppm CYA with the Dichlor, stop at 30 - 35ppm.
Be careful when using Dichlor as it can get out of hand quickly. For every 10ppm of chlorine added with Dichlor, you'll raise the CYA by 9ppm. For every 10ppm of chlorine added with Trichlor tabs you'll raise the CYA by 6ppm.
Shock at night then retest in the morning. Keep filtering 24/7. As the CYA starts to rise you'll notice the chlorine will hold longer. Remember to allow for 1 full turnover of the water before retesting.
If you make an adjustment then retest after an hour you're not going to get an accurate reading. A turnover is normally about 8 - 10 hours.
You're doing a great record keeping job. You're notating everything and looking for patterns. That's 1/2 the battle.