Part 01 · What your machine needs
°dH, gpg or ppm: how to read a maker's hardness limit
Makers write hardness in German degrees, French degrees, grains per gallon or ppm. Here is how they convert, and where a number can mislead.
The short answer
One °dH is 17.848 ppm as calcium carbonate, one French degree is 10 ppm, and one US grain per gallon is 17.118 ppm. So ECM's common limit of 4 °dH is about 71.4 ppm. We convert every limit to ppm and say when a number is our conversion.
The units you'll see
- °dH, German degrees of hardness, common in ECM, Profitec and Jura manuals. One °dH is 17.848 ppm as calcium carbonate. La Marzocco gives the same factor in its own water calculator.
- °f or °fH, French degrees. One °fH is 10 ppm as calcium carbonate. Bezzera and Rocket Espresso use them.
- gpg, grains per US gallon, common on US pages. One gpg is 17.118 ppm as calcium carbonate. LUCCA rounds it: "85 parts per million (PPM) or 5 grains per gallon (GPG)".
- ppm, parts per million, the same as mg/L for water. We use it for every comparison on this site.
From the maker
La MarzoccoLa Marzocco machines (Technical Center Water Calculator; names no model)
“(Optimal range suggested by La Marzocco) ... Alkalinity [ppm] | | 40 | 80 ... One degree KH corresponds to the carbonate and bicarbonate ions found in a solution of approximately 17.848 milligrams of Calcium Carbonate (CaCO 3) per litre of water (17.848 ppm).”
A worked example: ECM's 4 °dH
Many ECM and Profitec manuals set a hardness ceiling of 4 °dH:
From the maker
ECMSynchronika II
“To protect your machine from limescale damage, only use water that‘s not too hard, with a hardness level of up to 4° dH.”
4 × 17.848 = 71.4 ppm. That's the figure you'll see on those machines' cards: "at most 71.4 ppm (our conversion of the maker's 4 °dH)". We always say when a number is our conversion.
La Marzocco prints all three units side by side, which makes a useful check on the arithmetic:
From the maker
La MarzoccoLinea Micra
“it is important that the incoming water be of a hardness greater than 7°f (70ppm, 4°d) and less than 10°f (100ppm, 6°d)”
"ppm" of what?
Hardness in ppm is usually stated "as calcium carbonate" (CaCO3), so different minerals can be added up on one scale. Some makers say so. Lelit's profile for the Bianca V3 does:
From the maker
LelitBianca V3 PL162T (incl. PL162T-120)
“Below you can see the profile that we suggest for a good and stable extraction: Parameter Range Chlorine (ppm Cl2) 0 pH 6,5 - 7,5 Total Hardness (ppm CaCO3) 0 - 110 Carbonate Hardness (ppm CaCO3) 40 - 75 Chloride (ppm Cl-) < 30 Sulphate (ppm SO4) < 50”
Others write only "ppm". When a maker doesn't state the basis, we keep the quote exactly as written and show it, but our check doesn't use it to decide. Guessing the basis could move a limit far enough to change a result.
Total hardness or carbonate hardness
Total hardness (GH) counts calcium and magnesium. Carbonate hardness (KH) is closer to what many water reports call alkalinity. Some manuals set limits on KH instead of, or as well as, total hardness:
From the maker
ECMMechanika Max II
“Only operate the machine with fresh drinking water. Water with a value of 2–6°dH KH* is ideal. If the water hardness is outside this range, it is recommended to use the water filter that comes with the machine in order to minimize limescale deposits in the machine and to improve the taste of the coffee.”
From the maker
MeticulousMeticulous Espresso
“Both are expressed in ppm (parts per million) as CaCO₃. ... Alkalinity (KH), also called carbonate hardness or buffer, is the amount of bicarbonate. It stabilizes acidity, but it is also the ingredient that combines with calcium when water is heated to form limescale. ... Alkalinity (KH) | 40 ppm | 30–50 ppm”
A test strip for one won't tell you the other. Test strips or a TDS meter explains which tool reads what.
Hardness ceilings, in each maker's words
| Maker | The maker's words | Source |
|---|---|---|
| ECMSynchronika (86274) | You should use water with a hardness of max. 4° dH in order to protect your machine from lime scale damage. | Source for ECM, Synchronika (86274) (opens in a new tab)Saved October 22, 2026 |
| IzzoIzzo Alex Duetto IV (Plus), plumbed-in mode | If your water is above 3 grains of hardness then a softening system should be installed to prolong the life of the machine. | Source for Izzo, Izzo Alex Duetto IV (Plus), plumbed-in mode (opens in a new tab)Saved October 28, 2026 |
| JuraE8 (2017) | If the water hardness is 10 °dH or more, we recommend using the filter cartridge. | Source for Jura, E8 (2017) (opens in a new tab)Saved October 29, 2026 |
| MieleMiele CM 7750 (en-US, CA) | Tip: If your water hardness is > 22 gpg (21°dH), we recommend using bottled drinking water instead (< 150 mg/ l Ca2+ ). | Source for Miele, Miele CM 7750 (en-US, CA) (opens in a new tab)Saved October 29, 2026 |
| Nuova SimonelliNuova Simonelli Oscar II | Water hardness cannot exceed 3gpg or 50 ppm. | Source for Nuova Simonelli, Nuova Simonelli Oscar II (opens in a new tab)Saved October 28, 2026 |
| ProfitecPRO 800 | You should use water with a hardness of 4°dH in order to protect your machine from lime scale damage. | Source for Profitec, PRO 800 (opens in a new tab)Saved October 27, 2026 |
| Quick MillQuick Mill Anita Evo | Three grains/50 ppm or less of hardness is acceptable to be used in the machine. • Note: Should your water’s hardness level exceed three grains/50 ppm, then it is strongly recommended that an in tank softener be used or a different source of water that has been tested for hardness. Some bottled water can be extremely hard and should always be tested before using. Using a Brita or PUR style pitcher or faucet filter does NOT remove any hardness from the water and should only be used in the machine if your water source is under 3 grains of hardness. Using hard water in the machine will affect its performance and may cause damage to the machine which is not covered under warranty. | Source for Quick Mill, Quick Mill Anita Evo (opens in a new tab)Saved October 28, 2026 |
| Slayer EspressoEspresso Single Group (installation cut sheet, Mar 2026) | Water hardness cannot exceed 50ppm, otherwise a ... water softener is needed | Source for Slayer Espresso, Espresso Single Group (installation cut sheet, Mar 2026) (opens in a new tab)Saved October 28, 2026 |
Every machine's own figure, converted to ppm where needed, is on its card on the espresso machines page.
Sources
Every quote above is the maker's own wording, saved with its link and date. We link only to the makers' own manuals and pages.
- La Marzocco, Water Calculator (La Marzocco Technical Center, techcenter.lamarzocco.com, page footer (c) 2023; linked as 'Water Calculator' from the La Marzocco IE water page and the LM Deutschland FAQ). maker site (La Marzocco Technical Center) (opens in a new tab), saved October 28, 2026.
- ECM, ECM Synchronika II user manual (Synchronika-II-2505-web.pdf, ecm.de). ecm.de (opens in a new tab), saved October 27, 2026.
- La Marzocco, Linea Micra manual MAN.31.05.1 EN-FR V1.0 (PDF created 2022-04-28), hosted on home.lamarzoccousa.com. maker manual (opens in a new tab), saved October 28, 2026.
- Lelit, Lelit Bianca PL162T V3 Extended Guide 2022 REV00 (models PL162T-EU, -AUS, -120, -100; PDF created 2022-05-06; Lelit document hosted by MaxiCoffee). maker document on retailer site (opens in a new tab), saved October 28, 2026.
- ECM, ECM Mechanika Max II user manual (BA V1.0, ecm.de). ecm.de (opens in a new tab), saved October 27, 2026.
- Meticulous, Water for Your Meticulous: Preventing Scale and Getting the Best Taste (Meticulous Home, Inc. Help Center; written by Roy Raanani, July 29, 2026). maker help center (opens in a new tab), saved October 28, 2026.
- ECM, ECM Synchronika user manual, item no. 86274, file Manual_Synchronika_H02-2024-02 (for machines built Feb 2024 on); ECM PDF hosted by Whole Latte Love. maker document on retailer site (opens in a new tab), saved October 22, 2026.
- Izzo, Alex Duetto IV Espresso Machine owner's manual by Chris' Coffee Service (PDF created 2017-11-30). US retailer manual (Chris' Coffee); importer status for Izzo not verified (opens in a new tab), saved October 28, 2026.
- Jura, JURA E8 (2017) Instructions for Use (US), J72604/E8/US-en/201704. maker manual, hosted by a retailer (Seattle Coffee Gear) (opens in a new tab), saved October 29, 2026.
- Miele, Miele Operating Instructions, Countertop Coffee Machine CM 7750, en-US, CA, M.-Nr. 12 639 560. maker manual, hosted by a retailer (P.C. Richard & Son) (opens in a new tab), saved October 29, 2026.
- Nuova Simonelli, Nuova Distribution USA, LLC, "Oscar II Spec Sheet", Version 3.0 (PDF created 2016-04-05; simonelliusa.com). US distributor (Nuova Distribution USA, LLC) (opens in a new tab), saved October 28, 2026.
- Profitec, Profitec PRO 800 user manual (ba-pro800.pdf, profitec-espresso.com). profitec-espresso.com (opens in a new tab), saved October 27, 2026.
- Quick Mill, Quick Mill Anita Evo instruction manual by Chris' Coffee Service (PDF created 2016-09-27). authorized US dealer manual (Chris' Coffee) (opens in a new tab), saved October 28, 2026.
- Slayer Espresso, Installation Requirements, Slayer Espresso Single Group (cut sheet, MAR 2026), Slayer support knowledge base 'Installation Cut Sheets - 2026'. maker document (opens in a new tab), saved October 28, 2026.
Questions
How many ppm is 1 grain per gallon?
17.118 ppm as calcium carbonate. LUCCA rounds it on its own page: "85 parts per million (PPM) or 5 grains per gallon (GPG)".
Is °dH the same as dGH or dKH?
They use the same degree. dGH is total hardness in German degrees, and dKH is carbonate hardness in German degrees. A manual that says "KH" means carbonate hardness, not total hardness.
Why doesn't the water check use every ppm figure?
When a maker writes ppm without saying what it's measured as, we can't convert it without guessing. We show the quote, labeled, but don't let it decide a result.
Mineral & Steam does not certify water as safe, guarantee protection from scale, corrosion or equipment damage, or recommend a machine as an overall purchase. It compares the water information you provide with documented manufacturer water requirements and shows the basis and limits of that comparison.