I was looking back at old posts regarding the use of borax to help stabilize ph and other beneficial qualities. What I don't understand is the calculation to determine how to arrive at 30-50ppm of borax in the water. My understanding is that 1ppm is the equivalent of 1:1,000,000. In practical use, this means that one pound of product (borax for instance) added to one million pounds of water (120k gallons) equals one part per million. Wouldn't that mean that to bring the level of borax to 40ppm in a 14k gallon pool, which is the equivalent of approximately 116,667 lbs, that about 4.6 lbs of borax would be necessary? The prior forums indicate that about 9 to 10 times this amount is required to reach that same 40ppm. What gives?
Use of Borax in pool water
- Thread starter martsem
- Start date
ewkearns
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Welcome to TFP! 
As with most parts-per-million (ppm) calculations they are standardized to a specific weight and in the case of borate products it is in ppm Boron which only has a molecular weight of 10.811 g/mole. Boric Acid, on the other hand, has a molecular weight of 61.83 g/mole so 5.7 times higher. 20 Mule Team Borax has a molecular weight for its sodium tetraborate decahydrate of 381.38 but contains 4 boron in each molecule so per boron this is 95.4575 g/mole so 8.8 times higher than ppm Boron units. This is why you need to add a lot more weight of product to get 50 ppm borates since that is in ppm Boron units.
You can use PoolMath to calculate dosing for you.
As with most parts-per-million (ppm) calculations they are standardized to a specific weight and in the case of borate products it is in ppm Boron which only has a molecular weight of 10.811 g/mole. Boric Acid, on the other hand, has a molecular weight of 61.83 g/mole so 5.7 times higher. 20 Mule Team Borax has a molecular weight for its sodium tetraborate decahydrate of 381.38 but contains 4 boron in each molecule so per boron this is 95.4575 g/mole so 8.8 times higher than ppm Boron units. This is why you need to add a lot more weight of product to get 50 ppm borates since that is in ppm Boron units.
You can use PoolMath to calculate dosing for you.