Let’s Just Call it Tetraborate
Borax or Boric Acid to Establish a Pool Borate Level?
If you use sodium tetraborate pentahydrate (let’s just use tetraborate), you will increase pH and total alkalinity in addition to raising borate in the water. The pH goes really high (near 9.0), and the TA almost doubles. This requires adding a large amount of acid to lower TA back to a target of 90 ppm, which will reduce pH much lower than 7.0. Then you need to aerate and create turbulence and splashing to raise only the pH. If you add soda ash to raise the pH back up, you will also raise alkalinity which makes TA too high. Establishing a Pool Borate Level.
Borax or Boric Acid in Establishing a Pool Borate Level ?
If you use boric acid to increase borate in the water, it will only lower pH by 0.2 and have no effect on total alkalinity.
Let’s do an example:
Pool volume: 15,000 gallons
TA: 90 ppm
CH: 350 ppm
CYA: 50 ppm
Goal: Increase borate (boron, chemical symbol B) by 50 ppm
Sodium tetraborate pentahydrate dose: 684.7 oz or 42.8 lbs
New pH: 8.97 and pH increase is 1.47
New TA: 204 and TA increase is 114 ppm
The acid dose required to lower TA from 204 to 90 ppm: 3.47 gallons of muriatic acid (31.4% HCl)
New pH: 6.32 and pH decrease is 2.65
New TA: 90 and the TA decrease is 114 ppm
But pH is now 6.32. You must aerate and make turbulence and splashing to raise only pH to 7.5. If you try to raise the pH with soda ash from 6.32 to 7.5, you will increase TA from 90 ppm to 312 ppm.
Boric Acid dose: 572.73 oz or 35.8 lbs
New pH: 7.3
New TA: 90 ppm
Done or you could aerate and cause turbulence to raise only pH from 7.3 to 7.5. Much easier.
Similar Article: The Use of Borates in Swimming Pools