measuring alkalinity of water

[craigmarshall]

Hi,

I am interested in measuring the hardness/alkalinity/acidity of my tap water - are all these the same thing, or can I convert between them?

I have a "RITCHIES wine & beer acid test kit", presumably I can use this as I used to with a PH paper at school, and get a number, and correct it with either an alkali or acid. I've read the sticky thread about this topic, but it demands an alkalinity expressed as mg/l, not as ph nor as an acid as mg/l, which is what my kit will provide.

Any way around this without buying more stuff? I can't ring the water company as we're on a farm and the tap water comes from a hole in the ground about 1/2 a mile away...

Thanks,
Craig

[Graham]

Ritchies test kit is an acidity test kit; it will not test for alkalinity. It is a solution of caustic soda - basically it is a bottle full of alkalinity.

For an alkalinity test kit you need the opposite - a bottle full of acid.

Depending upon whether Ritchie buy it in from a professional standardised source, or mix it up themselves, it did occur to me months ago that it could be useful for testing the accuracy of home-made alkalinity test kits. However, my guess is that they mix it up themselves, in which case it is unlikely to be accurate enough.

[craigmarshall]

Okay chaps, thanks for the info, I'll go for the salifert kit next time.

Cheers,
Craig

[craigmarshall]

Well I bought a salifert KH/Alkalinity Profi test kit. Here are the results:

For tap water: 143 mg/l
For filtered water (through the sainsbury's cheapo "brita" filter): 34.5 mg/l

I get the impression from the sticky thread on alkalinity that I should be fine with these numbers. I guess I should just use filtered water if I make a pale ale or lager, and normal tap water is fine for everything else. Please correct me if I'm wrong.

I bought some gypsum a while ago. Should I be using gypsum and/or campden tablets in my brewing liquor, given the above info? I don't think we have any chlorine in our supply, it comes from a spring - is this a safe assumption (I certainly can't taste any, anyway).

Thanks,
Craig

[OldSpeckledBadger]

Ph is a measure of acidity.
Alkalinity is a measure of the resistance to a change in ph (with the addition of an acid).

When I was studying for my BSc Hons in Chemistry pH was actually a measure of hydrogen ion activity. As far as I'm aware it still is. It can be applied equally to acidic or basic aqueous solutions. Alkalinity is a measure of the ability to neutralise acid i.e., raise the pH towards 7. Solutions which are resistant to pH change are called buffer solutions. The average home brewer may not need to worry about these exact definitions though

[craigmarshall]

If your water comes via a treatment plant it will contain chlorine, otherwise it probably wont.

No - It comes from a pump in a small shed in a nearby field, which draws literally from a hole in the ground (and doesn't always work that well), so fairly sure it's chlorine free.

Don't use the filtered water as it may contain an ion exchange system to lower the bicarbonate and increase the sodium levels (which can result in an unpleasant harsh bitterness).

Thanks for explaining the problem, I will not use the filter for brewing liquor in that case.

I am slightly worried about the slight sediment we get from our tap water though (in the bottom of the kettle etc. (Not limescale). There are no odd tastes to our water though, and clearly it's certified safe, so I don't worry about it in that sense. I just wanted to keep the grit/solids out of my beer. Can I filter with something else, like my fine nylon mesh bag, or perhaps a coffee filter? Does anyone else have this issue? I did rack my beer through a fine nylon mesh bag as there were a few loose bits of protein etc. on the surface that didn't want to drop.. It worked fine. I could just put the same bag over the tap as I fill up the boiler.

With an alkalinity of 143mg/l CaCO3 you can add 0.63 mls per litre of Brupaks CRS direct to your water to reduce the alkalinity down to ~30mg/l CaCO3 for your pale ales and bitters.

Thank you - that saves me a calculation. Now if only I could find it for sale from somewhere that didn't charge the same again or double for postage...

Can I use citric acid in place of CRS? I could gradually add it until I reach a specified pH, and then record how much acid it needed...

Cheers,
Craig

[craigmarshall]

You can use citric acid and the mash ph can be adjusted emprically (i've done it myself with CRS and Phosphoric), the result isn't as reliable though and with citric acid you can end up with beer that tastes a little like fanta if you use a lot, lactic, sulphuric, hydrochloric or phosphoric are the prefered acids, CRS being a blend of hydrochloric and sulphuric acid, designed for the job.

Thanks for all these helpful answers and comments Chris and others.

Okay - so I should probably hang on and get the right stuff (CRS) for the job. Although with water heading towards the soft end of the scale, I probably wouldn't need to add all that much, maybe one day I will try it if I run out of CRS, I want as little as possible to go wrong at this stage though, so I will kit myself out properly to start with. I will let you know how it goes - might be a little while yet, next batch will be a full size one and I have a boiler and mash tun to make. I have all the parts now though...

Cheers,
Craig