Measurement units - just curious

[joemkraus]

I know that it makes no difference, but just curious to know. I cannot find anything about the units of our measurements. For example an FC=6 is 6 what? is that ppm (parts per million), ppl (parts per liter). and are all measurements the same units eg. PH=7.8? Thanks if anyone knows

 

[IceShadow]

PPM. All are the same except pH which is just a test of current acidity/alkalinity.

 

[joemkraus]

OK, thanks. That's what I thought, but today in reading an article about pools opening post covid-19, they said as long as "FC=3 parts per liter or more", so I think they just got it wrong. And yes of course was not thinking about PH being a ratio, but yes makes sense

 

[IceShadow]

Probably. If it were parts per liter you’d need to know what “parts” means. Otherwise it’s meaningless. Grams per liter? Picograms per liter? Etc.

 

[JamesW]

Most measurements are ppm except phosphates, which are ppb (parts per billion).

Chlorine is reported in standardized units of chlorine gas (Cl₂).

For example two pounds of chlorine gas in 1 million pounds of water is 2 ppm.

PH is the negative log of the hydrogen ion concentration (molarity).

For example, a hydrogen ion concentration of 2.5 x 10^-8 moles per liter is a pH of 7.6.

-log(2.5x10^-8) = 7.6

10^-7.6 = 2.5 x 10^-8

TA is in units of calcium carbonate. It's not actually calcium carbonate. It's reported in standardized units of calcium carbonate, which is equivalent to that much calcium carbonate.

Calcium is also in units of calcium carbonate.

So, if you added 100 lbs of calcium carbonate to 1 million pounds of water, the TA and calcium readings would increase by 100 ppm.

Cyanuric acid is in units of cyanuric acid.

Salt is in units of sodium chloride. Salt is sometimes reported in grams per liter by salt systems (Jandy Aquapure is grams per liter. Aquarite can be changed to metric where it will report in grams per liter). 1 gram per liter is 1,000 ppm.

Borates are in units of boron.

Phosphates are usually reported in parts per billion.

Phosphates can be reported in units of phosphorus or phosphate.

I think that most tests report in standardized units of phosphorus.