RO Filter performance

This is a continuation from the TM's spreadsheet thread discussion with A.J. Delange about the TA measurement I received from Wards lab. Started a new topic because I was getting close to hi-jacking the original thread.

I completed the drop test with a higher resolution per A.J.'s direction and found a TA of 15ppm on my RO. My RO system is tankless and was designed for aquarium use. I feed the RO with ion exchange softened well water. Below is my pre & post water sample results from Wards.

Pre RO(softened well water)
ph - 7.5
TDS(est) - 276
EC, mmho/cm - 0.46
C/A, me/L - 3.6/4.7
Na - 6
K - <1
Ca - 38
Mg - 17
Hardness, CaCO3 - 166
NO3-N - <0.1
SO4-S - 12
Cl - 4
CO3 - <1
HCO3 - 236
TA, CaCO3 - 193

Post RO
ph - 7.3
TDS(est) - 176
EC, mmho/cm - 0.29
C/A, me/L - 1.2/2.6
Na - 5
K - <1
Ca - 11
Mg - 5
Hardness, CaCO3 - 48
NO3-N - <0.1
SO4-S - 3
Cl - 4
CO3 - <1
HCO3 - 138
TA, CaCO3 - 113

I rely on my drop test results for alkalinity, disregarding Wards because they never gave me a solid explanation why it is high. I add CaCL2 for most beers and if I'm brewing a stout or porter use a 4:1 ratio of RO to hard water. If I'm brewing a pale ale I emphasize the sulfate more than the chloride with gypsum. I've looked at most of the available spreadsheets for profiles and use them occasionally to check myself but mostly go on past experience, tweaking the water as needed to suit my taste.

Now that I see the TDS numbers I am convinced that your sample got mis-labeled or contaminated or some of the ions got measured on your sample and some on someone elses.

A functioning RO system should reject at least 90% of almost everything so that your 276 feed water shouldn't read above 28 at the output (for reference, at the moment my feed is 160 and the permeate is 4). Your results show sodium reduced by 20 % and chloride not at all. I suppose, there could be a serious problem with your unit but I doubt that's it. The large imbalance between anions and cations in the Ward labs results points a finger at a problem in the testing.

I'll be pulling some samples in the near future as I try to keep track of my well, soft and RO water. My well is shallow, around 45ft and I have very low flow 1-2gpm. I'm just in a bad area, everybody around me as low output issues. So needless to say we conserve water every way possible so we don't draw the well empty and have to wait for it to catch up. Eventually I'll put in a storage reservoir so we don't have to regulate showers with washing clothes.
Anyway back to the water testing issue, do you know of other labs. My county health department will test water but they don't provide a complete lab report for brewing and I'm still curious about your statement in a previous thread about shipping samples can skew the results.

I'm afraid I can't recommend any other labs (I do all my testing myself) but I know you can find them in the phone book, in the Grainger catalog (you buy a kit of empty bottles, fill them up and Fedex them off - the testing is prepaid when you buy the thing) etc. The problem is that none of them, that I've ever seen, gives you the set of stuff that Ward Labs does at the price. I think they did screw up on your RO sample but at the price they provide and awfully good service for brewers, IMO.

The problem with shipping is that the sample can lose CO2. This happens with more with samples with at low pH since much of their carbo is in the form of dissolved CO2. This can throw an acidity measurement way off but brewers aren't really interested in acidity, just alkalinity and alkalinity is little effected. Just as an example a sample with 6 mmol/L carbo at pH 6, where 70% would be carbonic, has an alkalinity of 88 ppm as CaCO3. This is not that unreasonable a pH for some wells, by the way. If such a sample stands to the point where the pH rises to 7 it will have lost 3.82 mmol/L as CO2 gas but it's alkalinity will be 89.5. That's not much of a change so you only need worry about shipping WRT alkalinity if you want the most precise analysis and there is really little need for that in home brewing.

The other problem with overnight shipping, and I think this was mentioned earlier, is that microbiological testing results can be skewed if the sample is not processed within 12 - 24 hours and is not kept cold between collection and testing.