CRS cockup or measuring cockup

[sladeywadey]

I tested my water this morning using the salifert test and it came out at 217 CAC03

So using Chris' logic, I calculate I need to add 23ml of CRS to get down to my target of 30mg

So I add the 23ml of CRS to my water, then after a quick stir, I leave to 10 mins and then another quick stir and then I sample the treated water. I put 2 drops of indicator in the 4ml sample and it immediately turns pink.. So it looks like I've overshot the CRS or measured the original alkalinity wrong. After measuring the tap water alkalinity again twice, each result was the same - 217mg CAC03. What am I doing wrong?

Here are my workings:

salifert ml reading just before going pink - .24 = 4.34 meg/l = 217 CAC03 (4.34*50)
Therefore measured cac03 level = 217
target - 30
cac03 to remove (per L) - 187
total water qty to use (L) - 22
total cac03 (mg/L) - 4114
crs mg reduction per ml - 180
total crs ML to add to total brew length - 23ml

[sladeywadey]

thanks for the reply Chris. My volume of water to treat is 22l so I'm not far off your figures (I rounded up to 23ml CRS from 22.856)

I'm reasonably certain the FV is accurate as I measured the water into it in 1L increments when I calibrated it after buying. I'm using a 10ml plastic syringe to measure the CRS so I'd assume that should be reasonably accurate. maybe not.

I'll look at the threads you quote. It is likely then that I'm not taking the sample measurement properly. Whatever, the measured CAC03 is definitely lower than the recent water report I got. I'll check it again.

[EccentricDyslexic]

i did a pedigree brew yesterday and for the first time i tested my alk after adding the crs and my test also turned pink within a couple of drops, but i recon as you are at the end of the measurment range its not so acurate...i recon im pretty close so will stick with my curent procedure. Also my mash PH is pretty much spot on every time...so somethings right!

steve

[sladeywadey]

just thought I'd update this - it was due to bad calibration of my buckets etc - my fault! recalibrated properly today using scales etc.. That would also account for my low efficiency on my last batch sparge etc!