Making the change from Volvic to home RO water.

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
Wattbe

#1: Post by Wattbe » Jun 12, 2019, 10:24 am

Hi there,

I've been using Volvic water in my espresso machines for the last 5 years. I've never had an issue with scale by using it but my current machine started to show signs that it might have some scale buildup on the steam boiler heating element. The issue, a constant 'fizzing' noise, was discussed at length in another thread over in the 'repairs' forum.
When I removed the element for inspection, there was slight scale buildup evident, nothing much and to be expected based on Jim's insanely long post.

Long story short, I descaled the steam boiler and have now made the switch to a counter top RO system - the Osmio Zero, based on recommendations over at coffeeforums.co.uk
It produces water at around 30-40ppm and then uses a remineralisation cartridge to add 20ppm to give a total, as measured by my TDS meter, of 61ppm.
I also tested the alkalinity using a KH/alkalinity test kit which gave a result of 45ppm and the PH using a digital meter backed up with those simple test strips of around 6.8.

The reason I'm putting all this down is because I've read a fair amount on the subject, and not being a chemist, I think that I have a basic understanding of what I'm trying to achieve.
My only concern was that the water might be too acidic and cause corrosion in the long run (I have stainless steel boilers with copper plumbing). I've read from respected posters on here and elsewhere that it could be risky having an alkalinity below 50ppm which mine is.
Is it worth me trying to raise it with a touch of bicarbonate of soda or is it close enough that it won't be an issue?
On a separate note, I made 2 espresso today using the new water and I definitely prefer it. I don't have the most refined palette in the world but it has a smoother/silkier mouthfeel to it, almost creamy without the thickness of cream if that makes any sense!

Any info/thoughts on this would be appreciated.

Cheers,

Ben

Edit: I received a more accurate, calibrated PH meter in the post today which indicated a PH of 6.52 which is lower than I'd like. I'm not sure that it's as accurate as it states though, as I tested it in the supplied buffer solution which was labelled as 4.00 but indicated as 3.72. Ironically the cheap £10 ebay meter indicated 3.97 and measures my RO water at 6.8
This is my first dabble with this kind of equipment, is it generally fairly accurate? I don't know how accurate the buffer solution is either.

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SiempreTuParceroMike

#2: Post by SiempreTuParceroMike » Jun 12, 2019, 11:44 am

Hi, Ben. I recently switched from Volvic to Crystal Geyser; the Volvic is no longer sold at a local market and the CG is. So far, I prefer the CG, but had considered mixing tap with distilled, distilled with minerals, or installing some sort of a system as you described. I don't believe the Osmio Zero is sold in the US, but I'm happy to hear it's giving you pleasing results.

Sounds like you're doing things well, but I'm going to follow this thread. You'll get some better/more specific advice from the local experts, I'm sure.

Best,
Mike

*from the proper source; variation in TDS and such is very different from one source to another
eager and self-proclaimed newbie

www.michaelckregler.com

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Peppersass
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#3: Post by Peppersass » Jun 12, 2019, 2:19 pm

Hello again, Ben.

I would trust the cheap pH meter, as the reading is much closer to the reference solution (assuming that's accurately measured!) You might purchase a pH reference solution from a reputable third party to check.

It looks like your RO/remineralization system is operating at the lower end of the hardness range, 30 ppm plus 20 ppm, so you're getting about 50 ppm, which is a little low for optimum extraction without scaling. Assuming the cheap meter is correct, a pH of 6.8 isn't cause for great concern. I seem to remember reading somewhere that 6.8 is the minimum recommended by LM. I would be concerned about a pH of 6.5, however.

Also, 45 ppm is a bit light for optimum extraction, at least according to the experts. As I recall, Jim Schulman recommends something like 70 ppm, which should get the pH at neutral or above. (Personally, I think coffee water chemistry more complicated, given that I get excellent extractions with 0 ppm hardness and 140 ppm alkalinity from my cation softener.)

I see no problem with adding a little bicarbonate to bring up the TDS and pH. I think bicarbonate of soda is acceptable, but most coffee water recipes I've seen use other chemicals. Here's an example recipe from George Howell that I've made. It uses potassium bicarbonate and magnesium sulfate, both of which are available from Amazon. You could add a pinch at a time of one or both of those until you get the desired TDS and pH (measuring each pinch so you can repeat the recipe.) Plenty of other coffee water recipes here on HB and on the web.

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homeburrero
Team HB

#4: Post by homeburrero » Jun 12, 2019, 4:08 pm

Wattbe wrote:My only concern was that the water might be too acidic and cause corrosion in the long run (I have stainless steel boilers with copper plumbing). I've read from respected posters on here and elsewhere that it could be risky having an alkalinity below 50ppm which mine is.
I wouldn't worry. If your alkalinity is 45 ppm (CaCO3 equivalent) then you are in the zone you need for corrosion protection. The SCAA has long recommended "at or near 40" and the newer 2018 SCA Water Quality Handbook says much the same: "Alkalinity should be at least 40 ppm CaCO3 (2.2°d) to insure that the water is sufficiently buffered to minimize the risk of corrosion."

And in your case since it's based on remineralized RO you have additional safety because you can assume that your levels of chlorides and sulfates, which are common in natural water and can promote corrosion, are low.

pH can be confusing to evaluate. A pH of 6.8 is lower than what you would expect for RO water at 25℃ remineralized with calcite to 45 mg/L alkalinity and at equilibrium with CO2 in the air. But it still is nearly neutral and should not be a problem. If you do a Puckorius pHeq calculation, which roughly predicts the pH to be used in Langelier calculations for steam boilers you get a nice neutral pHeq = 6.96 for an alkalinity of 45 ppm.

If you wanted to play it super safe and do a bicarbonate spike, that wouldn't be difficult and would do no harm. You could use potassium bicarbonate or plain old baking soda sodium bicarbonate. But in very tiny amounts -- For example, you could make a concentrate by adding 1.0 gram of potassium bicarb to 500ml of RO that you keep in the fridge (that's a 20 mmol/L KHCO3 solution), then for each liter of water that you add to the espresso machine reservoir, add a tablespoon (15ml) of your concentrate to get a 15 ppm (as CaCO3) bump in alkalinity. (if using baking soda you would use a little less - about 0.8 gram in the 500 ml concentrate.)
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

Wattbe

#5: Post by Wattbe » Jun 12, 2019, 7:27 pm

Thank you for the great replies - it's given me a lot to think about and more importantly, it's clarified what I'm trying to achieve and how to actually achieve it!

I've got some bicarbonate of soda lying around in the kitchen, but I might grab a bag of potassium bicarbonate if that's a better way to go.

How long would you say I could safely keep the 500ml concentrate in the fridge for? With such tiny amounts being used, it'll take a while to get through 500ml of it. I was hoping to avoid having to add anything to the RO water but in all fairness, just adding a tablespoon of concentrate to a litre and mixing isn't really a hassle.

Regarding the PH tests, I find them quite frustrating as I don't know which one is actually accurate. I was hoping that a branded, pre calibrated test meter would stop the goal posts from moving so to speak but in reality, it's just added to the the blurriness. I'm going to try and source a certified buffer solution to test as I have no idea if the test solution supplied with the meters is in any way accurate either.

Just for clarification, if I add the 15ml of concentrate to a litre of my RO water, raising the Alkalinity by 15ppm, how much will that raise the PH by? If I look worst case and my water has a PH if 6.5, would that 15ml of concentrate raise the PH back up to 7ish?

Thanks again for the advice.

Cheers,

Ben

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homeburrero
Team HB

#6: Post by homeburrero » Jun 13, 2019, 1:58 am

Wattbe wrote:Just for clarification, if I add the 15ml of concentrate to a litre of my RO water, raising the Alkalinity by 15ppm, how much will that raise the PH by? If I look worst case and my water has a PH if 6.5, would that 15ml of concentrate raise the PH back up to 7ish?


It would not change it that much - maybe raise it to 6.6 or 6.7. But I wouldn't worry too much about measuring pH in espresso machine water - just go with the alkalinity, which is a better measure for machine health purposes (and also for extraction and taste predictions). The pH is highly dependent on dissolved CO2 and carbonic acid in the water which can change with exposure to air and temperature changes.

If you know the alkalinity, one way to calculate an effective pH for the superheated water inside the steam boiler is to use the Puckorius equilibrium pHeq. (It's appropriate for doing Langelier Saturation Index calculations.) Here are some example values:

Alkalinity . . pHeq
ppm as
CaCO3
------------------------
15 . . . . . . . 6.26
30 . . . . . . . 6.70
45 . . . . . . . 6.96
60 . . . . . . . 7.14
75 . . . . . . . 7.29


For the pHeq equation and discussion see Jim Schulman's Insanely Long Water FAQ.


P.S. For an interesting and easy to read discussion of pH, alkalinity, and extraction by Marco Wellinger, check out the very recent article in SCA magazine: https://scanews.coffee/25-magazine/issu ... e-issue-9/
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

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homeburrero
Team HB

#7: Post by homeburrero » Jun 13, 2019, 2:59 am

Wattbe wrote:How long would you say I could safely keep the 500ml concentrate in the fridge for?
I noticed that I neglected to answer that one. And have no expertise about that. Googling sure turned up a lot of nonsense. The concentrate will have no chlorine disinfectant, so would be comparable to bottled water with no chlorine. The Nestle Pure Life advice for their pure (no chlorine) water is probably conservative and they advise (here) that once opened, the bottles can be stored in the fridge for up to 2 weeks. Of course a lot depends a lot on how hygienic you are about handling the bottle. I use glass swing-top 750 ml bottles for my concentrate and use it up in about 20 days.

To be cautious you could always go with a half recipe in 250 ml and replace that every 2 weeks.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

Wattbe

#8: Post by Wattbe » Jun 13, 2019, 5:02 pm

Thank you for all the information Pat - it's very much appreciated.
That article you referenced regarding the significance of alkalinity was an interesting read.
I ordered some PH calibration powder yesterday, accurate to a PH of 0.01 apparently and calibrated both PH meters with it. I tested my water post calibration and got readings of 6.7 and 6.75.
Based on this, combined with my alkalinity readings of 45ppm and a TDS of 61ppm, I'm tempted to leave it as is. Based on what you've said (if I've understood correctly!) and on the article you referenced, it seems to be within an acceptable range to prevent both scale and corrosion.

Thanks again for sharing your knowledge with me - I certainly have a better understanding of water now than I did 3 days ago!

Cheers,

Ben

Stanford55

#9: Post by Stanford55 » Jun 14, 2019, 5:04 pm

@wattbe, or anyone who'd like to chime in: I'm curious to know what you're using to measure the TDS and alkaline levels.

Thx

Tim