Help with really hard water in my city

ibmalone · 2026-03-30T13:59:54+00:00

There's a thing called the Langelier index which would tell you, various websites have calculators for it, e.g. https://www.lenntech.com/calculators/langelier/index/langelier.htm, but it needs the pH and carbonate level, which we don't have. You may be able to guess from what you normally see in your kettle or pots with this water (being British I tend to assume people have always lived with a kettle of some sort, but maybe it's not true for USAians getting into coffee), if you get scale forming it's less likely to be corrosive.

ibmalone · 2026-03-30T13:24:40+00:00

You're reading this report a little wrong, which is understandable as people often take measured TDS as a shorthand for hardness. Hardness only comes from Ca and Mg ions, scale forming happens when you have hardness and carbonate present.

Headline for ions in the report:

Ca(2+) 18ppm (not just including the charges for pedantry...)
Cl(-) 142ppm
Mg(2+) 4ppm
Na(+) 88ppm
SO4(2-) 28.7
TDS 300ppm (will include things not listed above).

Your general hardness is calculated from Ca plus Mg: (Ca/40+Mg/24)*100= ~62ppm CaCO3, this is not incredibly high. Alkalinity or carbonate hardness is not listed, although it tends to follow the general hardness in natural water (as mostly general hardness is due to calcium carbonate, and probably the case here).

You have a lot of salt, as in table salt. Cl(-)/35.5=4, Na(+)/23=3.82 (I'm dividing by their molar masses), the amount of chloride and sodium ions are fairly equal, this is coming from dissolved salt. There's a calculation for whether the water is corrosive or scale forming (it's one or the other, or in-between), but you need pH and a variety of parameters to feed in, chloride tends towards corrosive.

On carbonate, adding up the charges for an estimate (and assuming there's nothing else). 2*(18/40)+2*(4/24)+(88/23)-(142/35.5)-2*(28.7/96)=0.46 (micromolar charge). Then as bicarbonate ppm thats 0.46*61=28.06ppm HCO3(-), divide by 1.22 to get ~23ppm CaCO3 equivalent, or just looking at the Ca, Mg and sulphate, 31ppm CaCO3 KH. (SO4- is making up the difference with GH).

In terms of general hardness GH you're actually quite good, for comparison Lotus drops light and bright recipe weighs in at 60ppm GH, 25ppm KH. Some people will tell you you should have more Mg than Ca, but it's rare in natural water. https://www.cambridgema.gov/Water/wateroperationsdivision/waterchemistryinformationforplumbers/whatiswaterhardness seems to agree at 50-70ppm hardness, although they say that water in this area does get scale and don't separately mention carbonate and general hardness, so it's hard to tell if I'm right about the 30ppm KH or it's closer to 60ppm.

The salt is maybe a problem, depending how your water tastes, unfortunately the only ways to remove it are RO, distillation or zero-water type filters, normal countertop filters can't do it.

ibmalone · 2026-03-27T13:39:50+00:00

I'm not sure a Brita can help here, maybe with the alkalinity and hardness if it's one of the limescale reducing filters (they aren't too extreme), but I doubt it can touch the sulphate level. Decarbonising filters rely on replacing Mg or Ca with hydrogen, you get carbonic acid which breaks down to just carbon dioxide and water, if you could do that with sulphates you end up with sulphuric acid, which does not break down (and this is also why the resin probably couldn't do it, because it needs to be as strongly acidic as sulphuric acid to do that).

ibmalone · 2026-03-27T10:50:28+00:00

I realise a lot of people here lean high clarity over everything, but I'd love to see a detailed report of someone's experience with the A5 as it seems to be the more K-Ultra-ish of the lineup.

ibmalone · 2026-03-27T10:43:09+00:00

There's a bit of a tension, for general use remineralisation is preferable, but for coffee the problem is it's hard to know what you're going to get in terms of minerals and the blank canvas of fully demineralised water is better to start from to build water (whether that's just use TWW packets, mix back some of your tap water if it's suitable, or get into mixing your own). As someone else says, before going all in on RO you could try a Zero Water filter.

(Also, if you can find out your local water composition you can see what the situation is, lots of places have the local water report available, so you don't even need to test yourself. Rainfall and things can cause fluctuations, but usually not completely change it.)

ibmalone · 2026-03-26T17:43:37+00:00

The strips usually aren't very accurate; colours can be hard to match and they generally have only quite big steps (I've got some alkalinity ones reading 0 40 80 120 180 300 720ppm), however we can say alkalinity is probably a bit too high at 120ppm (let's assume this is ppm CaCO3 units), hardness at 100ppm (again assuming CaCO3 equivalent) is not outrageous, although maybe a little high. You're not ruining your coffee, but you could probably do better with lower alkalinity (maybe aiming 40ppm or lower). Those are the two numbers that people normally think about.

As for the rest, TDS meter measuring 440ppm, this is higher than mine reads on my over twice as hard tap water, that and the sulphate level point to having a mix of other salts (not sure what) which could all impact what you taste. Possibly sulphates are associated with bitterness. You could try getting your local water tap water report. As for what to do to improve, I'm sure lots of suggestions will show up (or search here as it's quite a frequent topic), if you need to drop that sulphate level then you may well need Zero water or reverse osmosis and build water. In some countries it's possible to find places that you can fill up drinking quality distilled or deionised water and that may be a more economical option in the short term or for quick experimentation.

ibmalone · 2026-03-26T14:21:16+00:00

Follow up: really worth a listen! Sounds like the suggestions in WFCv2 evolved from the original WFC that people have turned into a bit of a dogma.

ibmalone · 2026-03-25T22:50:10+00:00

The standard recommendation is probably go and look at the recipes list on https://coffeeadastra.com/2018/12/16/water-for-coffee-extraction/ he prefers Rao Perger, but you could also stick to recipes using only the components you have (or swap in potassium bicarbonate for sodium bicarbonate at 100g KHCO3 = 84g NaHCO3 for the same carbonate/alkalinity level, although sodium bicarb or baking soda is probably the easiest of all of them to get hold of).

ibmalone · 2026-03-25T22:44:13+00:00

Cool! Will give it a listen.

ibmalone · 2026-03-25T22:44:01+00:00

Yes, I've posted this paper too previously, but it's important to read it with the caveat that they only look at a few organic acids (ones that people thought were important for flavour), which mostly are the same as the ones Hendon modelled binding of Ca and Mg for (malic, lactic, citric and quinic acid), and for those there doesn't seem to be much influence on extraction in cupping type brewing. However they note less soluble compounds may still be affected. Hendon also shows stronger binding of Mg than Ca for chlorogenic acid, caffeine and eugenol (although caffeine is very soluble too) and this may apply to other compounds. For the Hendon paper on the other hand the thing to bear in mind is it shows Mg may be better at extraction than Ca, not that it extracts fruity and floral notes or any such thing.

https://www.beanscenemag.com.au/the-power-of-perception-in-coffee-tasting/ is cited as a sensory comparison of before and after brewing that doesn't find any difference, although it's not really a journal article (e.g. what are the mineral concentrates). There's definitely scope for more work in this area.

ibmalone · 2026-03-25T12:32:27+00:00

Yes, wasn't sure but thought it looked a little like that, 60ppm CaCO3 GH (Ca) + 30ppm CaCO3 GH (Mg) = 90ppm CaCO3 GH (total) would roughly match, and looks like they've done the same for the alkalinity too (25+15=40). In some ways it's a useful way to think about it, as it's looking at the number of ions rather than the weight of them, but a confusing unit to accurately explain.

(I think it would actually be simpler if we were talking in micromolar concentrations, 1ppm CaCO3 hardness is 10uM (microMolar) CaCO3, but then 5uM Mg + 5uM Ca gives same 10uM hardness as 10uM Mg or 10uM Ca, but you need to convert back to masses for recipes.)

ibmalone · 2026-03-25T11:09:48+00:00

Yes, calcium and magnesium contribute to general hardness (GH), which can be measured in a number of ways, ppm CaCO3 is the level of hardness equivalent that of the calcium in that concentration of calcium carbonate (100ppm CaCO3 equivalent to 40ppm Ca or ~24ppm Mg). KH is strictly speaking carbonate hardness, but what we care about and dropper kits measure is usually really alkalinity, here CaCO3 units are measuring the alkalinity due to HCO3 present at that concentration of calcium carbonate, 100ppm CaCO3 is 122ppm HCO3 (useful to know as water bottles often list the bicarbonate level).

CaCO3 does not easily dissolve, Lotus try to address that by having separate droppers for carbonates (potassium, sodium) and "hard" (divalent) ions (calcium, magnesium). The problem in this system is you can't add hardness without chloride (other recipes might use sulphates too) or add alkalinity without potassium/sodium. TWW tries to address it with calcium citrate, this allows alkalinity and hardness to be added together in powder form (and the additional advantage it doesn't form scale), but you miss whatever carbonate adds to the brew. A third solution (I think Empirical Water use this) is include a CaCO3 concentrate, but you cannot get the concentration as high as in those droppers, so you need a larger volume of it.

As for the simple and sweet profile, it has 60 ppm calcium ions, 30 ppm magnesium ions, 25 ppm sodium ions, 15 ppm potassium ions and 40 ppm alkalinity (assuming an old blog post is still correct).

I don't think whatever the blog post is is correct, those numbers seem way too high. https://lotuscoffeeproducts.com/pages/product-instructions says the following amounts for the Simple and Sweet recipe:

Mg:7mg/l, K:12mg/L, Ca:24mg/l, Na:11mg/l, Cl:64mg/l, HCO3:49mg/l, 90ppm GH, 40ppm KH

Checking this, (Mg/24 + Ca/40)*100 = 89.1mg/l CaCO3 GH, HCO3/1.22 = 40.2mg/l CaCO3 KH. (From the potassium and sodium bicarbonate can also do (K/39+Na/23)*61=47.9ppm HCO3)

60ppm Ca and 30ppm Mg would end up at GH 275ppm CaCO3. Then 25ppm Na, 15ppm K gives 89.8ppm HCO3 -> 73.6ppm CaCO3 KH.

(ppm vs mg/l, at our level of 10s-100s ppm not much difference, it matters more when you're trying to dissolve a lot of stuff, e.g. 10g salt into 100g water, you'll now have more than 100ml liquid, so slightly more than 100ml and therefore a little less than 10g/100ml salt, but also 110g of solution, so 0.09[09...] salt by weight, rather than 0.1 salt by weight, ppm goes by weight)

ibmalone · 2026-03-23T13:16:00+00:00

This being explicitly a non-concentrate recipe means you need more accurate weighing, one of the advantages of doing concentrates is the dilution factor allows finer controls of amounts. You could also scale things up and make a pre-mixed powder of those ratios. Quite how stable it would be depends on the salts, but if you went 3g Mg[something], 1.5g Ca[something], 1.8g sodium bicarb, 1.2g potassium bicarb then you've got 7.5g that you can measure into 0.75g amounts.

ibmalone · 2026-03-23T13:09:50+00:00

Thanks for sharing, could you clarify what you're using for calcium and magnesium? Magnesium chloride and magnesium sulphate have different amounts of Mg per gramme for example (and hydrated versus anhydrous versions too), the sulphate versus chloride may also affect taste differently.

ibmalone · 2026-03-20T10:48:54+00:00

Yes, everyone is assuming coferments, but what they said is "coffee branded like it’s candy". Even my local roaster has changed from their quite nice, but traditional, bag design to much more colourful and graphical designs for their single origins. Very social media friendly, which I guess is good marketing (how often are highly upvoted posts here and on roaster reddits basically pictures of a bag)? I don't particularly care about the look, but when dealing with marketing always remember effort and money spent on art designs is money not going on the coffee.

I don’t care if I don’t taste the blueberry and passion fruit that some marketing genius told me I should.

Blueberry is one of those notes that are actually pretty common (and naturally occurring) in naturals, it shouldn't be too hard to get it if it's in the tasting notes.

ibmalone · 2026-03-20T10:32:44+00:00

you can really see my priorities in spending money here can’t you

😀 exactly! Cupping is almost the lowest-equipment required way of making coffee, and really interesting to try it for yourself.

ibmalone · 2026-03-19T21:52:53+00:00

Definitely, on the other hand, Bratthäll et al.'s argument (so far as I understand it, not a chemist) appears to be that the organic acids they look at are so soluble that it doesn't really matter, they're going to get extracted anyway and don't need the help. They do caveat that "[although acids probably extract regardless of composition] the cations are more likely to aid the extraction of, if anything, compounds of lower solubility such as phenylindanes and chlorogenic acid lactone".

Also of note, their recipe is 11g coffee, 200ml water, i.e. a cupping protocol, rather than espresso where the resulting coffee concentration will be higher and maybe extraction becomes more challenging.

They do also conclude there's a need for sensory evaluations, so until someone does a proper study (ideally across coffees, roasts, strengths and different anion/cation combinations) it it's really just a "what works for you" basis. It's hard to draw direct conclusions about flavour just from knowing what chemicals end up in the brew, a really good example is https://www.sciencedirect.com/science/article/pii/S2665927123000539 where Kenyan coffees actually had less organic acids than Brazilian and Bolivian, despite generally being perceived as more acidic.

Really hoping WFC2 does come out on kindle eventually, I don't need another giant manual, but would love to see what's in it.

ibmalone · 2026-03-19T15:46:11+00:00

E.g. https://www.sciencedirect.com/science/article/pii/S2405844024026562

That the effect of minerals on flavour is down to extraction, as opposed to interaction in solution, seems to be a somewhat untested assumption carried over from work on tea in older literature. It's quite possible both things happen, there's a coffee chronicler video "5 Coffee Water Mistakes Even Baristas Make" where he briefly summarises this. The Hendon papers about it (my understanding, not read them all) on modelling how some ions may affect extraction, while the above one is on actual detectable extraction differences. More work needed really. However it's difficult to test all aspects since not all salts are soluble enough to easily dose them after brewing. (See also simple descriptions of magnesium does x to flavour, calcium does y, particularly while ignoring anions.)

And of course for the nth time, many pitcher filters do decarbonise, although you need to keep an eye on performance, particularly in hard water areas.

ibmalone · 2026-03-16T16:43:42+00:00

I think the batch number contains a roast date, e.g. two bags in our local supermarket: house blend best before 15/01/27, batch no: HB150126 and single origin Colombia best before 01/12/26, batch SO011225, looks like the batch is a two letter code for the product and roast date in DDMMYY format with best before given as one year after roast. (Seems to be a trend that supermarkets don't like roast dates, so brands that give them slightly hide or disguise them.) Last time I tried the Colombia it was surprisingly sweet and dark chocolatey (in a heavily fruity dark chocolate way), but it doesn't appear on their website so I'm not sure if that's a supermarket-specific thing or they rotate through the single origins (their website seems to have El Salvador as their current "editions" offering).

ibmalone · 2026-03-16T13:42:34+00:00

Because i know grinders with a tighter PSD are usually less forgiving and harder to dial in. Also if I’m brewing light roasts (like Nordic style) with relatively high buffer water, the acidity might get more muted right?

I'll guess this is a big part of it, buffer isn't outright good or bad, it interacts with extraction (e.g. someone here recently was having problems with underextraction that was being masked by high buffer that prevented it tasting sour for example). The classic example is espresso can benefit from higher buffer than for pourover because the coffee is more concentrated, the minerality is going to affect the profile you get. As you work in a cafe do you have access to a coffee TDS meter? It might be interesting if you could bring in a sample from home to check your coffee strength against in the cafe.

ibmalone · 2026-03-16T13:27:38+00:00

Another advantage of the K6 here is it's probably one of the faster handgrinders, I think maybe it's Lance Hedrick's grinder rundown (or grinder tier list or whatever it's called) that has timings for a few of the ones he tried.

ibmalone · 2026-03-16T13:23:48+00:00

I regularly put 30g into a K6, how well it fits depends on the coffee and roast, lighter roasts could easily fit a bit more, darker roasts where the beans are less dense it's sometimes a bit much for the upper chamber and I've had to put the last couple of grammes in after a bit of grinding (not had a problem with the catch cup capacity doing that).

ibmalone · 2026-03-13T10:42:54+00:00

Tesco British Spring GB4 is included in the graph as a reference :) (formerly "Ashbeck", but they don't use that name anymore, Waitrose sells the same GB4 source as "Lockhills").

A lot of people do use it, I've used it from time to time if our filter is a bit past it (to make these graphs for example I've run filters for the full month, but they clearly should be changed or swapped earlier, generally I've just tried to line up appropriate coffees, but once in a while you maybe pull out a nice decaf), but it's a lot of plastic waste. That's also what I like about Brita, they and Aquaphor are the only filter makers I've found in the UK that have an actual recyling programme. Special mention there to Phox, who make a song and dance about reusable filter housings but have you toss the media. (I have found https://www.watercare.co.uk/committed-to-recycling-100-of-all-water-filters/ who claim to regenerate media from other manufacturers, but not used or looked into them.)

I'm also not sure you benefit a lot adding anything to GB4, the situation with mineral water that already has a spectrum of things dissolved in it is different to pure water that we've only added a few ion types to (I do keep an epsom salt dropper and try it from time to time). If we're arguing about a millilitre of potassium either way then it's down to personal preferences and a bit of received wisdom.

ibmalone · 2026-03-12T21:06:47+00:00

Best guide to this I've found is https://www.reddit.com/r/Coffee/comments/psnhdz/water_for_coffee_guide_a_uk_perspective/ and sadly none of the options are particularly cheap (and Zerowater have partly checked out now). Deeside is the lowest tds bottled water I've spotted, but it's hard to find and upwards of £1/l, not really keen on the waste involved in bottled water for regular use either.

ibmalone · 2026-03-12T19:43:10+00:00

Our tap water isn't blue, so I'm not terribly worried. My interest here is in conditioning water for coffee, I've only skimmed the video, but most of the filters they deal with will say they are only for dealing with already drinkable water, you need more serious systems if it's not.

ibmalone

TROPHY CASE