Best Water for Espresso Machines: How to Read Your Water Test Report
Coffee University · Water & Filtration
Best Water for Espresso Machines: How to Read Your Water Test Report
A plain-English guide to every column, unit and result on a lab water report — and what each one means for your coffee and your machine.
Every great espresso starts with an ingredient most cafe owners never think about: water. It makes up more than 90% of a shot of espresso and almost all of a cup of brewed coffee. Yet when a lab report full of columns like MDL, PQL, GPG and NTU lands on your desk, it can read like a chemistry exam.
Water quality matters for two reasons. The first is taste: the minerals in your water control how flavor is pulled out of the coffee. The second is your equipment: the wrong water slowly coats a machine in scale or eats away at it from the inside. La Marzocco says proper water treatment is how cafes get great espresso and extend the life of their machines (La Marzocco, Water Quality Episode #2). This guide translates your report line by line, unit by unit.
The short version
- The best water for an espresso machine has 80–150 mg/L TDS, 30 mg/L or less chloride, zero chlorine and a pH between 6.5 and 8.0.
- A lab report that is green on every line can still be wrong for espresso. Green means "under the EPA drinking water limit," and those limits are far looser than any espresso machine spec.
- Chloride is the line to check first. It doesn't form visible scale, it causes pitting corrosion in boilers, and only reverse osmosis removes it.
- 1 mg/L = 1 ppm. To convert hardness in grains per gallon to mg/L, multiply by 17.1.
- Get a full lab panel before installation. Test strips won't show chloride in mg/L or calculate the LSI.
Part One
The best water for espresso machines: cheat sheet
Keep this table next to your report. Compare your Observed Value for each test to the espresso target, not just to the Regulatory Limit. Each line is explained in detail further down.
| Test | Espresso target | EPA limit | If out of range |
|---|---|---|---|
| TDS | 80–150 mg/L | 500 mg/L (guideline) | Reverse osmosis with blending or remineralization |
| Total hardness | 70–150 mg/L as CaCO3 (4.1–8.8 GPG) | None | Scale-reduction cartridge or reverse osmosis |
| Alkalinity | 40–75 mg/L as CaCO3 | None | Dealkalizing cartridge or reverse osmosis |
| pH | 6.5–8.0 (7.0 ideal) | 6.5–8.5 (guideline) | Depends on the cause — ask your technician |
| Chlorine / chloramine | 0 mg/L | 4.0 mg/L | Activated carbon |
| Chloride | 30 mg/L or less | 250 mg/L (guideline) | Reverse osmosis only |
| LSI | +0.10 to +0.70 | None | A balanced filtration system |
| Iron | 0.02 mg/L or less | 0.3 mg/L (guideline) | Reverse osmosis or a dedicated iron filter |
| Turbidity | Under 1 NTU | 1 NTU | Sediment prefilter |
Targets based on La Marzocco's published water specifications, SCA ranges as reported by Barista Magazine, and Bean and Brew Technologies installation practice. Always confirm against your machine manufacturer's current specification.
Part Two
Why "safe to drink" is not the same as "good for espresso"
The EPA's guideline for total dissolved solids is 500 mg/L, and for chloride it is 250 mg/L. These secondary standards aren't enforced; the EPA describes them as guidelines to help public water systems manage taste, color and odor (U.S. EPA).
An espresso machine is far less forgiving. La Marzocco's specification caps TDS at 150 ppm and chloride at 30 ppm (La Marzocco).
Part Three
Understanding the columns on your lab report
A typical commercial water test, like the Pentair H2O Express report we use for installations, lists each test as a row with the same set of columns. Here's what each column means.
| Column | What it means in plain English |
|---|---|
| Long Test Name | What was measured, such as Chloride or Total Hardness. "(Est.)" means the value was calculated from other results rather than measured directly. "Total as CaCO3" means the result is expressed as if it were all calcium carbonate — a standard way to compare minerals on one scale. |
| Observed Value | The actual result for your water, and the number you compare to the targets in this guide. Many reports color-code it: green for within the regulatory limit, yellow or red for a value worth attention. |
| Unit | How the result is measured: usually mg/L, sometimes GPG or NTU (explained below). pH and LSI have no unit. |
| MDL (Method Detection Limit) | The smallest amount the lab's test can reliably tell apart from zero (Minnesota Department of Health). A result of "0" really means "below the MDL," not literally zero. |
| PQL (Practical Quantitation Limit) | The lowest level the lab can report as an accurate number. A result between the MDL and the PQL means the substance is present, but the exact amount is an estimate. |
| Regulatory Limit | The EPA drinking water standard for that item. Some are enforceable health limits (lead 0.015 mg/L, arsenic 0.010 mg/L); others are non-enforceable taste and appearance guidelines (TDS 500 mg/L, chloride 250 mg/L). "NA" means there's no federal limit. These limits are for drinking, not for espresso machines. |
Part Four
The units: mg/L, ppm, GPG and NTU
- mg/L (milligrams per liter): the most common unit on a water report. For water, 1 mg/L is the same as 1 ppm (part per million), so a chloride reading of 30 mg/L is 30 ppm. Manufacturers like La Marzocco usually write their specs in ppm.
- GPG (grains per gallon): an older unit used mainly for hardness and by the water softener industry. 1 GPG = 17.1 mg/L. A hardness of 105.4 mg/L as CaCO3 equals 6.17 GPG, and you'll often see both on the same report.
- NTU (Nephelometric Turbidity Units): measures how cloudy the water is, by shining light through the sample and measuring how much is scattered by tiny particles. Lower is clearer. The EPA requires treated public water to stay at or below 1 NTU (EPA).
- No unit (pH and LSI): pH runs on a 0–14 scale. The LSI is an index that can be positive or negative.
Part Five
What each test means for espresso
Total dissolved solids (TDS), mg/L
TDS is the total amount of minerals and salts dissolved in the water. Pure water reads 0 mg/L. Some minerals are good: they give espresso body and help extract flavor.
- Above 150 mg/L: La Marzocco describes unbalanced body and acidity, low aromas and a harsh taste, plus mineral build-up in the machine.
- Below 75 mg/L: espresso tastes weak and tart, and the water becomes aggressive against the machine's metal parts (La Marzocco).
The SCA recommends 75–150 mg/L (Barista Magazine). Our installation target is 80–150 mg/L. If your report says "TDS (Est.)," the lab calculated it from the other results, so confirm it with a handheld TDS meter at install.
Total hardness as CaCO3, mg/L and GPG
Hardness measures calcium and magnesium — the minerals that leave white crust on a shower head and limescale inside a boiler. The USGS scale is soft (0–60 mg/L), moderately hard (61–120), hard (121–180) and very hard (over 180) (USGS). In grains, that's roughly 0–3.5 GPG soft, 3.5–7 moderately hard, 7–10.5 hard and over 10.5 very hard.
La Marzocco's machine specification is 70–100 mg/L. Its water guide warns that above 150 mg/L (8.8 GPG) you get over-extraction, a harsh, bitter taste and heavy scale, while very soft water produces a flat body, low aromatics and little or no crema. Your report may also list Calcium, Total and Magnesium, Total separately; together they make up most of the hardness number.
Alkalinity as CaCO3 and bicarbonate, mg/L
Alkalinity, mostly bicarbonate, works like a sponge for acid. Some is good. Too much soaks up the coffee's bright, fruity notes and drives limescale when the water is heated. The SCA range is 40–75 mg/L, and excess alkalinity can dull acidity (Barista Magazine). The "Bicarbonate (Estimated)" line is calculated from alkalinity, so the two track together.
pH (no unit)
pH 7.0 is neutral, and La Marzocco calls it ideal for espresso. Below pH 6.5, water tastes sour and becomes more corrosive. Above pH 8.0, espresso tends toward bitterness, and with high hardness the boiler becomes prone to scale. Target: pH 6.5–8.0.
Chlorine (total and free) and chloramines, mg/L
Towns add chlorine or chloramine to keep water safe. The EPA allows up to 4.0 mg/L, but in espresso even small amounts react with coffee compounds to create a medicinal taste, and chlorine increases corrosion. La Marzocco allows no more than 0.1 ppm total chlorine. Target: 0 mg/L. Activated carbon removes it, which is why carbon is part of nearly every espresso filter. "Chloramines (Calculated)" is total chlorine minus free chlorine.
Chloride, mg/L: the silent machine killer
Don't confuse chloride with chlorine. Chloride is a dissolved salt found in groundwater, in coastal areas and in regions that use road salt. It doesn't form visible scale, so it often goes unnoticed until a boiler fails. La Marzocco warns that chlorides cause severe pitting corrosion and can only be removed by reverse osmosis.
High Sodium, Total and Sulfate, Total results often travel with high chloride, and both add to TDS.
Langelier Saturation Index (LSI), no unit
The LSI combines pH, hardness, alkalinity and temperature into a single number that tells you whether water tends to scale or corrode. Above +0.70, water forms scale. Below +0.10, it tends to dissolve minerals and attack metal. Target: +0.10 to +0.70. A reading of −1.0 is a clear corrosion warning. La Marzocco's free water calculator works it out from your report.
Turbidity, NTU
Turbidity shows whether particles such as silt or rust are floating in the water. Anything under the EPA's 1 NTU limit looks clear. For espresso, low turbidity protects flow meters, valves and filter cartridges from clogging. A sediment prefilter handles high readings.
Silica, iron and metals, mg/L
Silica is a natural mineral that, at high levels, forms a hard, glassy scale. Iron can give milk drinks a greenish tint and a bitter, metallic flavor; La Marzocco's spec allows only 0.02 mg/L, far below the EPA's 0.3 mg/L guideline. Copper, lead, manganese, selenium, barium and arsenic are health-based tests — for these, follow the Regulatory Limit column. Copper or lead readings near their limits (1.3 mg/L and 0.015 mg/L) can also point to corroding pipes in the building.
Part Six · Case File
A real report, decoded
Here are results from a recent lab test at an office in northern New Jersey where we're installing an espresso machine. On the original report, every line the lab measured against an EPA limit came back green — only hardness was flagged yellow. Now look at the espresso column.
| Test | Observed | EPA limit | Espresso target | Verdict |
|---|---|---|---|---|
| TDS (Est.) | 326.9 mg/L | 500 mg/L | 80–150 mg/L | Too high |
| Chloride | 90.9 mg/L | 250 mg/L | 30 mg/L or less | 3× too high |
| Sodium | 54.9 mg/L | None listed | As low as possible | Elevated |
| LSI | −1.0 | None | +0.10 to +0.70 | Corrosive |
| Total hardness | 105.4 mg/L (6.17 GPG) | NA | 70–150 mg/L | Acceptable |
| Alkalinity | 65.7 mg/L | None | 40–75 mg/L | OK |
| pH | 7.2 | 6.5–8.5 | 6.5–8.0 | OK |
| Chlorine, total | 0 mg/L (below 0.01 MDL) | 4.0 mg/L | 0 mg/L | OK |
| Turbidity | 0.16 NTU | 1 NTU | Under 1 NTU | OK |
| Iron | 0.007 mg/L | 0.3 mg/L | 0.02 mg/L or less | OK |
Green: within the EPA Regulatory Limit, as shown on the lab report Yellow: flagged by the lab for attention Uncolored: no limit applied on the report
Source: Pentair H2O Express lab report, northern New Jersey commercial site, 2026. Observed Value colors reproduced as printed by the lab.
Hardness — the only line the lab highlighted in yellow — is the least of this site's problems. The real problems are lines that showed green: 326.9 mg/L TDS, 90.9 mg/L chloride and a corrosive LSI of −1.0.
A standard scale cartridge would have done almost nothing here. The right answer is reverse osmosis to bring chloride well under 30 mg/L, followed by a remineralization stage that restores calcium, magnesium and bicarbonate so the water lands between 80 and 150 mg/L TDS. Without it, this machine's boilers would be at real risk of pitting corrosion — damage that shows up as an expensive repair, not a slow decline in taste.
Part Seven
How to test your water the right way
La Marzocco recommends drawing samples from a cold-water tap that isn't already filtered or softened, using a fresh sample for every test, and testing at each location, because water varies from site to site. Our technicians add:
- Get a full lab panel before installation. Test strips are fine for spot checks, but they won't show chloride in mg/L or calculate the LSI.
- Re-test after any change. A new well, a new softener or a change in your town's supply can change everything.
- Check TDS at every filter change. A handheld TDS meter confirms your system is still delivering 80–150 mg/L.
- Use the manufacturer's tools. La Marzocco's online water calculator interprets results and suggests a treatment type.
For a deeper look at filter types, read our Espresso Machine Water Filtration Guide, and see How Often Should You Service Your Commercial Espresso Machine for maintenance schedules.
FAQ
Frequently asked questions
What is the best water for an espresso machine?
Filtered water with 80–150 mg/L total dissolved solids, 70–150 mg/L hardness, 40–75 mg/L alkalinity, 30 mg/L or less chloride, zero chlorine and a pH between 6.5 and 8.0. For a plumbed-in commercial machine, the way to get there is a filtration system matched to your water test — carbon for chlorine, scale reduction for hardness, and reverse osmosis with remineralization if chloride or TDS is high.
Can I use distilled water in an espresso machine?
Not on its own. Distilled and pure reverse osmosis water have almost no minerals, which makes espresso taste flat and makes the water aggressive toward the machine's metal parts. Many machines also use the water's conductivity to sense boiler level. Pure water should be remineralized back into the 80–150 mg/L TDS range before it reaches the machine.
Is ppm the same as mg/L?
Yes. For water, 1 mg/L equals 1 ppm, so a 150 ppm TDS spec and a 150 mg/L lab result mean the same thing.
How do I convert grains per gallon (GPG) to mg/L?
Multiply GPG by 17.1. For example, 6 GPG of hardness equals about 103 mg/L as CaCO3.
My water report is all green. Is my water fine for espresso?
Not necessarily. Green usually means the result is under the EPA drinking water limit. Espresso machines need much tighter ranges — for example, 30 mg/L or less of chloride compared with the EPA's 250 mg/L guideline.
Will a water softener protect my espresso machine?
Not always. A standard softener swaps calcium and magnesium for sodium. It reduces scale, but it doesn't lower TDS or chloride, and the extra sodium can make the water more corrosive. La Marzocco recommends caution with sodium-based softeners.
What does the Langelier Saturation Index (LSI) tell me?
Whether your water is likely to deposit scale or corrode metal. A positive LSI above about +0.70 points to scale; a value below about +0.10 points to corrosion. For espresso equipment, aim for +0.10 to +0.70.
Not sure what your own report means? Send it to us and a technician will review every line.
Sources
References
- La Marzocco. "Water Quality – Episode #2: La Marzocco Water Ranges Explained." lamarzocco.com
- La Marzocco. "La Marzocco Water Specifications." lamarzocco.com
- La Marzocco Tech Center. "Water Calculator." techcenter.lamarzocco.com
- U.S. Environmental Protection Agency. "Secondary Drinking Water Standards: Guidance for Nuisance Chemicals." epa.gov
- U.S. Environmental Protection Agency. "National Primary Drinking Water Regulations." epa.gov
- Minnesota Department of Health. "How to Interpret Drinking Water Lab Results." health.mn.gov
- U.S. Geological Survey. "Do you have information about water hardness in the United States?" usgs.gov
- Castillo, Angel. "Something in the Water — How Water Chemistry Impacts the Taste of Coffee." Barista Magazine, May 12, 2026. baristamagazine.com
Not sure what your water report means?
Send us your results. A Bean and Brew technician will review every line and recommend the right filtration for your machine and your coffee — before scale or corrosion turns into a repair bill. Serving New Jersey, New York, Connecticut and Pennsylvania · 973-283-5568.
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