Alkalinity, Testing Your Tap Water

[mitch]

Just to let everyone know, There is a far better test kit on the market that can be used to work out your waters alkalinity

I've been using a Salifert alkalinity/carbonate hardness test kit for a few months: they are crap. Firstly the indicator solution is ready mixed into the reagent so if your water is anything less than very alkaline you will be adding tiny amounts of indicator and consequently find it difficult to impossible to identify the end point. Also, by using one acid for your reagent and a different acid to treat your water you are compounding any errors introduced by variations in the acid's concentrations. If I could get hold of some pH indicator solution then I would follow DaaB's water testing procedure and throw away my Salifert kit.

[mitch]

Can you convert alkalinity in meq/l expressed as calcium hardness obtained using the kit into alkalinity in mg/l expressed as CaCO3 ?

(ALK in mg/L as CaCO3) = 50 * (ALK in meq/L)

[beesley121]

mitch not quite understanding what you are saying.

These test kits are unbelievably accurate!! We use them everyday for a company that makes millions in the chemical industry.

can you tell me what results you get for your water from daab kits?? then tel me how you go about testing your water with the salifert kit and I will try to see where you going wrong as i can asure you that these kits are the bee's knees

[Graham]

mitch not quite understanding what you are saying.

These test kits are unbelievably accurate!! We use them everyday for a company that makes millions in the chemical industry.

can you tell me what results you get for your water from daab kits?? then tel me how you go about testing your water with the salifert kit and I will try to see where you going wrong as i can asure you that these kits are the bee's knees

No way can it be more accurate than the method that Chris is advocating. The only possible source of error is the accuracy of measuring volumes. It is also self compensating to a degree, because the same acid is used to do the determination as is used to do the alkalinity correction.

Saifert say this on their web site:
The only difference between alkalinity and carbonate hardness is a conversion factor.
Quite frankly a company that makes a stupid and inaccurate statement like that shouldn't be trusted to inflate a bicycle tyre, leave alone produce an accurate test kit.

[mitch]

mitch not quite understanding what you are saying.

My main problem with the Salifert kit is that the indicator is ready mixed with the acid. This means that you add pH indicator (the colour changing dye) in proportion to the reagent (acid). If your water is lowish in alkalinity then you will only need to add a small amount of acid before your pH crashes and the dye changes colour, but because you are also adding only a small amount of colour changing dye the water may not appear very coloured at all and you will find it difficult to observe the transition.

If your water is quite alkaline then the kit would be better than nothing, but still useless is you wanted to check your alkalinity after water treatment.

DaaB's method will always be more accurate for the reason Graham just mentioned but also because the transition is easier to spot (because you can add the colour changing dye until you are happy you can see what colour it is in solution). Also the Salifert kit will only give you 200 tests if you use a 2ml sample of water: far too small a sample for accurate results using this method.

[adm]

I just happened to pass a tropical fish shop earlier today, so popped in and bought one of the Salifert Alkalinity test kits.

Bear in mind that i've never used one of these things before, so I've got no basis for comparison, but here are my thoughts anyway....

First, i was amazed at how easy it was and how quick to do the test. After spending hours talking to the water company, I could have just got on and done it!

The process was easy. You add 4ml of tap water into the little test tube (from the graduated 5ml syringe), and 2 drops of the blue dye. Then you fill up the small syringe with the other test solution (1ml, graduated in 1/100 ml) and drip a drop at a time into the test tube. The drops that come out of the syringe nozzle are very small - maybe 1/100 ml?

The test tube liquid starts out blue, but turns pinkish once you get to the right point. I was worried the colour change might be slight, or too subltle for me - but it was very clear indeed - I couldn't miss it. It changed colour quite definitely with the difference of one drop of solution.

Anyway, the test came out to read 134 mg/l CaCO3 equivalent. I tried it 3 times, and it came out with the exact sam eresult each time, so i am comfortable with that.

However - my water company tells me the total alkalinity is 108 mg/l CaCO3 - so there's a fair old difference between the two numbers. So my question is, which should I use - or should I just average the two?

My feeling is that the water company test number is a year old and wasn't taken on my exact tap water, so the test kit number is more likely to be right. What do you guys think?

As for the price - it was £7.99 for the kit which can do 100-200 tests, although 100 is what you'll get if you use the full 4ml per test. Still - 8p a test is fine with me if it helps me take my beer up a level!

[mitch]

Salifert must have recently changed the design of their kit because the kit I bought a few months ago contained just one bottle of a red chemical (a mixture of acid and pH indicator). The instructions were to measure out 4mL of water into a beaker and then add drops of the red chemical to the beaker using a 1mL syringe. After adding about a third of the syringe of red chemical the water takes on a blue tint and continuing to add drops of the red chemical eventually causes the colour of the water sample to become pink. The volume of red chemical remaining in the syringe is then looked up in a table to determine the alkalinity.

It sounds as if the new Salifert kits have separate bottles of indicator (the blue stuff) and acid, which makes the test more like DaaB's.

[adm]

Salifert must have recently changed the design of their kit because the kit I bought a few months ago contained just one bottle of a red chemical (a mixture of acid and pH indicator). The instructions were to measure out 4mL of water into a beaker and then add drops of the red chemical to the beaker using a 1mL syringe. After adding about a third of the syringe of red chemical the water takes on a blue tint and continuing to add drops of the red chemical eventually causes the colour of the water sample to become pink. The volume of red chemical remaining in the syringe is then looked up in a table to determine the alkalinity.

It sounds as if the new Salifert kits have separate bottles of indicator (the blue stuff) and acid, which makes the test more like DaaB's.

There's a 3rd bottle there as well. I have no idea, but i think it's a known value "check solution" but it's not mentioned in the instructions. It's still the same "look up the remaining volume in the syringe on the table" thing though.

I'll take a picture of all the bits in the kit and post it in a bit.

[adm]

To revive this thread a bit.....I've got a few more questions on water treatment as i think I screwed it up in my last brew......

I have one of the Salifert test kits and it seems to be giving me pretty repeatable results, however I am confused as to whether it is actually measuring total Alkalinity, or Hardness !!!!!!

The result I get is about 140mg/l CaCO3.

My water company say the Total Alkalinity figure is 108mg/l CaCO3.

BUT - they also say the Hardness is 145mg/l CaCO3.......which seems suspiciously close to the test kit result.

Any ideas?

Finally, one question on amounts of water to treat.

I will use CRS to treat the entire amount of water in my HLT - about 46l.

However - for the mineral salt additions I am confused as to whether to calculate them on the actual target brew length, or the volume of water used to get to that brew length

For a 23l brew, I have about 31l that goes into the boiler (hop absorbtion, dead space and evaporation), but about 38l that goes through the mash tun (grain absorbtion and tun dead space).

So - should I add salts to treat for 23l or for 38l ??

On the last brew, I treated for 38l and I think I have too much mineral salt in the resulting batch, (particularly sodium chloride) which I think has created a hostile environment for the yeast as I have a stuck fermentation problem. It's stopped at 1022 for the last couple of days and a repitch with SO4 has done nothing.

[adm]

Chris,

I certainly am! I have to add about 0.52ml of the reagent to a 4ml water sample to get the colour change, and the conversion chart supplied with the kit says this is a KH value of 7.7 i dKH (whatever that means), or an Alkalinity figure in Meq/L of2.74

Multiplying that by 50 gives me a CaCO3 figure of 137 mg/L.

I think that's how it works anyway.....

[adm]

What's more, the kit says "Carbonate Hardness / Alkalinity" test kit....and all the stuff I have read here says these are NOT the same at all. But there's only instructions to do one test and get one single number.....

[Andy]

Slight diversion: Chris, any idea on how long the CRS dilute solution in your test will last for ? I've got some made up in March '08 and am wondering if it will still be OK to use.

[Andy]

Ta, yup used distilled.

[adm]

I believe the 50x equation is correct - I found a couple of online converters that used the same number.

Oh well. I think i'll do another test tomorrow before i get a bre on, then do the CRS correction then do another test to see if it's roughly where I think it should be.

As for the stuck ferment, I've bunged in some dry beer enzyme and we'll see what happens with that!

If the problem is that I have to many dextrins, does that indicate the mash temperature was too hot? (Shouldn't be an issue though as the thermomenter said 67.4...)

[mitch]

I have to add about 0.52ml of the reagent to a 4ml water sample to get the colour change, and the conversion chart supplied with the kit says this is a KH value of 7.7 i dKH (whatever that means), or an Alkalinity figure in Meq/L of2.74

The left-most column in the conversion table (that was supplied with my kit) is the volume of reagent remaining in the syringe. If you filled the syringe with 1mL of reagent and used 0.52mL then 0.48mL remains in the syringe so your ALK would be 2.97meq/L or 149 mg/L as CaCO3. Check you are using the the table correctly.

I am confused as to whether it is actually measuring total Alkalinity, or Hardness !!!!!!

The Salifert kit you have is almost certainly measuring alkalinity not hardness and not carbonate hardness (as the kit's box implies).
Try following DaaB's alkalinity test kit procedure using the bottle of coloured indicator solution from the Salifert kit and see if you get a similar alkalinity figure. If you have any pH test strips (pH 3.8 to 5.5) then check the pH of the test solution just before and after the colour change. The pH just after the colour change should be ~ pH 4 and the pH just before should be a bit higher. You could also check the pH of your liquor after CRS treatment to check that you are not over dosing.

My water company say the Total Alkalinity figure is 108mg/l CaCO3.

Most water supplies don't have totally stable ALK levels over time, a fluctuation of 25-30 mg/L as CaCO3 is quite possible.