Post-reverse osmosis water remineralization options for pH control

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
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#1: Post by TheMadTamper »

So I'm making a ton of changes to the espresso setup, including moving toward a plumbed setup (in progress.) Well, a Flojet driven plumbed setup. Various position/location issues as well as not just trusting it being fully plumbed in after an "ice maker incident" led me to a manual-fill of the bottle from the tap situation to a Flojet bottle. We'll call it "semi-plumbed". Nearly all the convenience, plus a lot of peace of mind by manually filling the reserve on demand. And some minor annoyances when it comes to large flushes.

The fine folks at Chris's have been spending *WAY* too much of their time helping me through all the minutiae of water, and are still helping, but since some of my questions are extending beyond the products they carry, I figure it's not fair to keep pestering them alone about it all, though even still, they're helping where they can! Those guys are rock stars! I can't praise them highly enough! As I shop for a new machine (the poor Duetto needs quite a bit of work, possibly due to water issues over the years that went unknown) it makes me a bit sad to be looking at some machines they don't stock. There's other great dealers, but these guys have been through the trenches supporting me, and it would feel wrong not having them behind the machine. Hard choice there: Buy the wrong machine because it's supported by the right people... Can't get much more praise than actually considering doing that! Those guys are top notch.

So back to water. My tap water, apparently, is saltwater, for no known reason. >60ppm chlorides. That explains a lot, from years of non-stop Duetto problems despite making my own water mixture with some tap mixed back in, to years of tub spigot disintegration from the inside out. Right now I've gone as far as getting a pump-boosted RO set up. Just a generic consumer under-sink one. Sitting in the open. Who needs dinner when there's espresso? It's up, it's running, it's quiet other than the Flojet doing 5 seconds on 5 seconds off, but the refill with the booster is reasonably fast. Waste isn't the best, isn't the worst. It's a kit that's been mentioned in other threads here, including a post about it being used by a Slayer dealer/cafe - iSpring RCC7P-AK. Good kit. But the remin cartridge is giving me some issues. They're a good company with good support, I'm working with them as well, but I have concerns over if dialing it in specifically for the needs of espresso is really in their wheelhouse and I might be going in circles not talking to some of you guys who seem to know a good deal on this stuff!

So right now, I have a feed water with a pH of 7.0-7.5 with an alkalinity of 80. I have not tested what comes straight out of the membrane yet, as I'd have to depressurize the whole thing. However what's coming out of the iSpring FA15 remin is a stratospheric pH.

Feed water:
TDS 170-210ppm
Total Hardness: 180-250ppm
Alk: 80ppm
pH: 7-7.5
Chloride >60ppm
Chlorine .1
Sulfide: 0
Iron: .25ppm

First flush out of FA15 remin after overnight saturation:
TDS: 400ppm
Total Hardness: 5-50ppm
Alk: 40-120
pH: 12.5 (!!!!)
Chloride: 0
Chlorine: 0

Output of FA15 remin after flushing anywhere between 1-6L:
TDS: 30-40
Total Hardness: 0-20ppm
Alk: 40
pH: 10.6-11.2 (!!)

I fear that pH would probably cause even the trace TDS to harden into rock on the element (or just corrode the copper anyway....) Let alone espresso taste (actually, I tried it, it tastes surprisingly good, though a Over time as the cartridge ages I'm sure it will drop somewhat. And I'm going to build out a bypass valve specifically so that with *any* remin, I can set it overnight to only send pure RO to the machine so it's not sending 400ppm saturated TDS junk into a boiler for the first refill call on a timer startup, then switch to remin after a line flush on first use. The few ounces of pure RO would easily be corrected by the higher TDS, higher pH water in the boiler from actual running versus trying to get massive mineral buildup out if letting it fill with the saturated stuff.

Still, for whatever reason it's way, way overperforming it's spec, taking a pH of 7.5 -> RO (should LOWER pH), -> remin -> 12.5. Even if I can fix it, it's a 6 month cartridge....trying to dial in a new one every 6 months if it's this much of a variable doesn't sound fun.

So what I'm wondering is, this is a Calcite+Corosex+"mineral stone" cartridge. Would I be better off just replacing it with a generic 10" Calcite filter like CC cells? Not as good mineral mix potential, but maybe more controlled pH without Mg?

Or would I be better off with one of the BWT systems like Bestmax Prem or Bestmin? I'd contacted WLL who contacted BWT, the initial recommendation was Bestmax Prem due to the Mg me, sending RO water into an IX sounds like a bad plan, or at least an ineffective plan - I may end up with acidic pH again, or without much/any Ca to exchange post-RO, it may do nothing at all. It sounds like it would have been cost effective with the S or V size, but I don't know enough to know if that's a bad recommendation.

Alternatively there's Bestmin. With the FlexHead bypass settings, I could *probably* control the initial flush TDS/GH + pH by just setting the bypass to max. But I don't know if that would be sufficient, or how much water that thing wants to flush. It also has the other problem: In the US, the M size seems to be the only available size. Flushing it daily is out of the question - much too much water in there. Plus it's expensive for a capacity I couldn't use if I tried within 12 months. BUT....If it's what works with the bypass head and larger mineral space...I'd certainly consider it. Nothing else really offers the same kind of single purpose flexibility. Not sure what I'd be getting into there (or if it could end up bringing me back to a scale problem.)

Or could there be other options I'm missing? The more dozens of hours I spend researching, including some of your posts here, the more options and confusion I end up with! This water thing has certainly been an (unwelcome) surprising adventure!

Water is truly the bane of espresso :roll:
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#2: Post by ira »

Saw this today, might be interesting: ... e-issue-9/


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#3: Post by TheMadTamper »

Update: So, apparently it is *not* the remin filter that's boosting the pH. It is boosting pH, but not far outside it's expected norms despite some over-performance. The real issue here is the RO process itself is RAISING the pH, rather than reducing it! Feed water is 7.5 pH or so. What's coming out of the RO with the remin removed is 8.5-10.5! Remin is then simply boosting *that* to 10.5-12.5.

Digging and searching I've found one or two references to the phenomenon, but RO increasing the pH seems like an exceedingly rare phenomenon. And it leaves me with quite a confusing mess to try to control. My current thinking is RO -> DI -> remin.....I can't think of any other way to reduce pH at this point. I just don't know if that'll actually be successful in pH reduction, and/or if there's any problem feeding pure/deionized water into a remin/calcite/corosex system. If it works, I"d hope the DI could bring me back to 6-8, and then remin could bring me back to 7.5-9.5 or so. 9.5 is still on the high side, but a lot more tolerable than double digits. I'd just hope it won't bring me into non-correctable acid territory. And hope similarly that it won't just do nothing.

BTW, Thanks for the link, ira! Interesting read. Doesn't help with the immediate conditions, but it does help understand targets!
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#4: Post by TheMadTamper »

Another update: I'm not certain about the pH of the RO water entirely now. It seems like the electronic pH meter may be struggling with RO or DI water. The basic pool test strips are showing more realistic values, with the RO closer to 7.5-8.0 which matches more closely the feed water. That still means RO isn't REDUCING pH as expected.

Feeding water into the either the BWT Bestmin or the iSpring FA15, I still end up with 11+ (off the chart of the pool strips that top at 9) pH, no matter the bypass setting I select. I put my own bypass valve in after it to mix the plain RO in with it. Electronic meter tells me 10.5+ PH is the result. Pool test strips tell me it's probably around an 8.8-9.0. A lot more sane if correct. BUT with that mix I end up with a hardness of 0-15 and a TDS of 18-20. I still have to figure out what it is about my water that's making remin filters (at least Mg remin filters?) spike the pH so astronomically above their spec. Vendor is looking into it, but I'm not expecting an easy result there. I'm thinking maybe it's due to the RO water having a higher than normal pH? Not sure why RO isn't reducing pH, even if it's leaving it mostly the same as start. 40 alkalinity, ph between 7.5-8 post-RO, then remineralizing to 11. GH isn't significant post-remin though....25-50ppm in general.

My next possible steps are to put a Brita/Mavea WAC *BEFORE* the RO....if I can get some H+ in there, I might be able to bring the pH down pre-RO and get the RO to bring it down a bit further...maybe the remin will be more gentle. The other idea is maybe feed the Bestmin water directly into a Bestmax Prem....maybe *IT* can exchange some of the Bestmin's hardness for H+ and get the PH down. BUT...then it adds its own Mg2+ back in. I could end up in the same, or worse position. (Or put the Mavea after the Bestmin to replace the new hardness with H+ - but then I may end up with 0 hardness and an acid bath. This is getting confusing and very expensive. :cry:
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#5: Post by CarefreeBuzzBuzz »

Your experimentation is why we opted to just make our water and not use our RO with remineralization. Results would be too inconsistent. Results making water were easy to replicate and there are only two of us. I am currently starting with distilled water at 80cents a gallon from Walmart. I am sure a few pennies can be saved somewhere along the line but since we just moved haven't sorted that out. Basically I add about 4 gallons to my 6 gallon tank every 3 weeks and its super easy. We are using an Aquatec pump with an RO type holding tank, and it cycles for only about 15 seconds every 3-4 days.

All that said you seem to enjoy the experimentation so keep letting us know what's up.
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#6: Post by TheMadTamper »

I haven't abandoned the thread, honest! Any of you that were following this saga deserve an update on the craziness of everything I tried here. I think I've finally settled on "usable" water. By usable, I mean I think it's pretty good for the machine, for now. Maybe not the best for won't win any WBC titles, but then again unlike a WBC competition, I can't afford to pour liquid limestone into a 3-group Aurelia for a single shot. :wink:

I mentioned in the last update I was going to try a Mavea Purity C Quell. I tried that, after the BWT Bestmin, and it worked at reducing the pH. The bad news is it worked too well. It dropped the pH to 5.5 and inexplicably shot the alkalinity up to 180! And that was at 70% bypass! Well, that won't work. Probably great for making descaling solution though.....or for dissolving gaskets. The Mavea was a waste for this use.

So then I ended up buying a BWT Bestmax Premium. I went with the M-size to match the only size of the Bestmin. I might be able to get away with a V size. MAYBE even an S size, but with S I'd have to watch my usage. V would be enough, but for a $30 difference I can be a lot more carefree with water with the M and use it for other things. I put that after the Bestmin at bypass 3 (40% if I recall?) That worked, but like the Mavea, it brutalized the pH. Not as severely though, and this one didn't muck with the alkalinity, unlike the Mavea. I had a 6.5 or so pH, and the same 40 alkalinity my RO starts with. It's close.... So I improvised. I put a tee at the Bestmin outlet, with a bypass line with a JG ball valve on it, going to another tee on the Bestmax outlet, and a checkvalve preventing backflow into the Bestmax. This means that from the exit of the Bestmin, the line splits, with one line going past the Bestmax right to the machine/tap line, and the other goes through the Bestmax. This has one negative side effect which means that my RO tank which should have around 30psi, or 2.2 bar or so, is barely the right pressure for BWT filters. Splitting the line like that means dropping the pressure below spec pressure for BWT filters. HOWEVER, it appears to work. The JG valve is very imprecise, so it's trial and error, but I've dialed it down so that with the 3 bypass on the BWT, and the bypass around it, only a small amount of water is going through the softener. Some of that softness is just Ca to Mg replacement, and some is hydrogen exchange. The resulting effect is I was able to bring the water down to about 25 hardness, 40 alk, and a pH of 7.2-7.8.

The LM water calcluator alternates between "slightly corrosive but non-scale forming" and "balanced". I wasn't QUITE satisfied so I fiddled a bit and got 25-30 hardness, 40 alk, and a pH of 7.8-8.4. The LM calculator alternates between green and "light scale forming" and "scale will form". This should still be a pretty low LSI and should hopefully keep scale very low to the point of not worrying about it. I'll have to re-balance for different seasons, but it feels like I have a fairly controllable output now. At least to a degree. It's a very EXPENSIVE annual process though, so I'll see how long I want to keep up with it, but it's also an "infinite" coffee water supply without worry. Bestmin and Bestmax are very pricy filters. Bestmin has way more capacity than I need. Though the two together also seem to act as an accumulator tank for the RO. After putting them in I can draw half a gallon or so without the RO even kicking on to refill. Combined with my anticipated lever machine I should have entirely silent espresso with a 10 minute refill afterward.

The Mavea for now is on ice maker duty. No point throwing out a $130 filter. It's more conveient than Berkey and it's softer water for ice (Berkey doesn't soften.) It might get some use for a water pot for hot chocolate, tea etc in winter. Maybe I'll keep buying Maveas for that use now that I have a spot for it.

Hardness should be higher out of the Bestmin, but I think the high pH out of the RO is preventing it from absorbing more minerals (strangely the iSpring "alkaline filter" absorbed a lot when sitting for a long time, too much, but then did next to nothing when running it. Bestmin is thoroughly consistent whether it sat for 8 hours, or just pumped a gallon through.)

So the convoluted setup now is: Flojet & bottle to an accumulator, to the RO, to the pressure tank, to the Bestmin to the Bestmax (with bypass), and finally to the machine/tap, with a Mavea split off from the accumulator before the RO to have some non-RO filtered/softened water for non-boiler use (chlorides...) The down side is I foolishly set it up in a way that protected the RO unit, however to pull it out to change filters ever 6 months I have to disconnect all the tubing in and out of it and lift it out! Hindsight is always 20/200.

I still don't understand why my pH is so high out of the RO. Neither does iSpring. They think it could be either a bad membrane or checkvalve out of the membrane. They did send me a warranty membrane to try. I haven't tried it yet since I have something workable. I might drop that in at the 6 month filter replacement time when I have the system drained for the pre-filers and see if the RO pH goes down at all. They're not confident that's it, and neither am I. The hardness, chlorides, and TDS all seem "normal" for RO, so it doesn't seem brine is really mixing with permeate. But it's also an extremely unusual outcome to have a slightly alkaline post-RO pH, apparently, and it's throwing Bestmin off by a mile.
CarefreeBuzzBuzz wrote:Your experimentation is why we opted to just make our water and not use our RO with remineralization. Results would be too inconsistent. Results making water were easy to replicate and there are only two of us. I am currently starting with distilled water at 80cents a gallon from Walmart. I am sure a few pennies can be saved somewhere along the line but since we just moved haven't sorted that out. Basically I add about 4 gallons to my 6 gallon tank every 3 weeks and its super easy. We are using an Aquatec pump with an RO type holding tank, and it cycles for only about 15 seconds every 3-4 days.

All that said you seem to enjoy the experimentation so keep letting us know what's up.
Chris's poor crew is ready to kill me. "Can't you just make ideal water now?" "No." "How about now?" "No." "It would be so much easier if you just made water." "No." :lol:

They'd really like to see me get the hardness up as well for better extraction but I'm content for now with healthy machines even if it's not ideal brew water. Heck, if the LM calculator can flash green, I figure I'm ok, even if they prefer rock water.

For me, I tend to use half a gallon a day or so on coffee, plus filing the Keurig with it etc as well, so bottled water would REALLY add up, and just be a hassle lugging home tons of bottles all the time. I checked out getting 5 gal jugs delivered, but the delivery costs as much as the water, and winter time would be a pain if they just leave water sitting outside at 15 degrees. So the convoluted system makes more sense, and ends up being much cheaper. Even at it's insanely expensive price. I could trim the Mavea out since it's just a luxury to have softened ice versus Berkey, and I could strip the Bestmax down to a V or maybe even S since I'm sending so little into it. That would trim the annual cost to about $400/yr. Which is still high. Still cheaper than $2.70/gal or more if I were to make the water, across the year though!

I could see doing maybe RO+DI and using that for Third Wave water or something. Then I could ditch the BWT stuff that's the truly expensive part, but I'd have to add a second Flojet (fill the bottle with one, then use the bottle with the other.) That's worth considering too....but I don't trust DI water for coffee. If it came down to it, though, it would work.
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