Water: pH to CaCO3 converter

[spencerwood]

Thames water can't give me total alkalinity. But a local fish centre has told me that the pH of the chessington tap water is between 8.3 and 8.5. Does anyone know how I convert from pH to the CaCO3 mg/l value so I can use it in all the water treatment calculators?

Thanks


Spencer

[crookedeyeboy]

You would need to titrate the water sample with acid to find out the level of alkalinity in the water.

pH is pretty useless to be fair until you get to the mash and final beer...

[spencerwood]

A lot of people in the other water treatment threads had been buying pH kits of various descriptions. I am guessing these kits give people pH values. Now I know my pH value from the water company, I just need to know how others get from their pH value to the CaCO3 value, typcially about 200 mg/l that is needed to work out how much CRS to add?

Thanks


Spencer

[Aleman]

People are buying the Total Alkalinity test kit by Salifert that gives you a value directly for Alkalinity in milli equivalents which can be converted to mg/l CaCO3 . . . A pH value tells you one thing . . . How many hydrogen ions you have in your water . . . and nothing else.

What you can do, is to use an acid of known concentration , with an indicator, to determine how much acid it takes to reach a certain pH point (pH4.3 IIRC). Then knowing how much acid you add and how much acid is required to neutralise x amount of carbonate you can calculate the alkalinity in the sample . . . This process is called titration, and is effectively what you are doing when you use the Salifert kit

[harry_mac]

This is the same Salifert test as I got http://cgi.ebay.co.uk/SALIFERT-CARBONAT ... 2c507da26c

[OldSpeckledBadger]

I just need to know how others get from their pH value to the CaCO3 value, typcially about 200 mg/l that is needed to work out how much CRS to add?

It can't be done with any degree of certainty. Hardness can be used at a push to get a rough estimate of alkalinity but really those test kits are so cheap that it's silly to just guess.

[coatesg]

In fact it's almost impossible to guess from pH to alkalinity. Alkalinity is a measure of how much the water will resist a change in pH. If you have water with moderately high alkalinity, and you add a small amount of acid, the pH will not change much. However, with water with low alkalinity and the same acid (or by adding enough acid to overcome the buffering effect of the various ions, mainly HCO3-) the pH will go shooting downward.

Use te salifert alkalinity kit for the indicator (your fish shop should have this too, or try a swimming pool shop).

[crookedeyeboy]

In fact it's almost impossible to guess from pH to alkalinity. Alkalinity is a measure of how much the water will resist a change in pH. If you have water with moderately high alkalinity, and you add a small amount of acid, the pH will not change much. However, with water with low alkalinity and the same acid (or by adding enough acid to overcome the buffering effect of the various ions, mainly HCO3-) the pH will go shooting downward.

Use te salifert alkalinity kit for the indicator (your fish shop should have this too, or try a swimming pool shop).

Yup or send to me and Ill test it!