Distilled Water (2025 Guide): What It Is, Uses, Safety & Buying Tips
Distilled water is purified by boiling water into steam and condensing it back to liquid, leaving behind most minerals, salts, and impurities. Freshly distilled water is very low in TDS (near 0–10 mg/L), tastes flat, and is prized for appliances and lab tasks that need mineral-free water. This page explains where to use it, when not to, and how to store or make it safely.
Note: This guide is informational, not medical advice. For infant feeding, medical devices, or specific health conditions, follow manufacturer and clinician guidance. Distilled water is mineral-free; if using it as your main drinking water, ensure minerals come from diet or consider light remineralization for taste.
Distillation Basics
Distillation boils water to steam and condenses it back to liquid, leaving most dissolved minerals, salts, and solids behind. The result is very low-mineral water with near-zero TDS and a “flat” taste.
How Distillation Works (At a Glance)
- Evaporation: Heating drives water to vapor; non-volatile minerals/salts are left behind.
- Phase change: Steam travels to a condenser (coil or finned radiator) and cools back to liquid.
- Collection: Condensate is routed through food-grade tubing (often via a small carbon filter) into a clean container (glass/HDPE).
- Taste: With minerals removed, distilled water tastes neutral/flat; many users remineralize lightly for drinking or coffee.
Chemistry Notes
- TDS (Total Dissolved Solids)
- Near zero in fresh distillate. Common spec: 0–10 mg/L.
- Conductivity
- Low ionic content → very low conductivity (often < 5–20 µS/cm). Rule-of-thumb: TDS ≈ 0.5–0.7 × conductivity (µS/cm).
- pH
- Fresh distillate approaches neutral, but absorbs CO₂ from air, forming mild carbonic acid → measured pH typically ~5.5–6.5. This is expected and not the same as “acidic” like soda.
Good practice: Use clean glass or food-grade plastic containers with tight lids; avoid touching the spout. Once opened, treat like normal drinking water and store away from heat/sunlight.
Distilled vs Purified/RO/Deionized
All four are “low-mineral” waters, but they’re made differently and labeled for different uses. Match the method to your device manual and target purity (TDS or conductivity).
Key Differences
| Water Type | How It’s Made | Typical Purity | Drinking? | Best Uses | Caveats |
|---|---|---|---|---|---|
| Distilled | Boil → condense steam → collect | TDS ~ 0–10 mg/L; Conductivity <5–20 µS/cm; pH ~5.5–6.5 (CO₂ exposure) | Yes (flat taste) | CPAP/humidifiers, irons, appliance/glass rinse | Not sterile; small VOCs may need post-carbon polish |
| RO (Reverse Osmosis) | Membrane separation; often + carbon/UV | TDS ~ 5–50 mg/L (depends on feed & filters) | Yes | General drinking, many appliances if low-TDS | Quality varies with maintenance; remin for taste if desired |
| DI / Demineralized | Cation/anion exchange resins | Conductivity often 0.1–10 µS/cm; TDS near zero | Usually no (often labeled “not for drinking”) | Lead-acid batteries, coolant mix, lab/industrial rinses | Can leach ions from metals; store in proper plastics |
| Purified (bottled) | Usually RO (may include DI, UV, ozone) | TDS typically <10–50 mg/L | Yes | Drinking, appliances where “purified/low-TDS” is allowed | Check label/spec: some add minerals “for taste” |
| Lab/Reagent Grades (ASTM I/II/III) | RO+DI+polish (tight controls) | Type I: 18.2 MΩ·cm (~0.055 µS/cm), ultra-low TOC | No (not a beverage) | Analytical instruments, assays | Expensive; specialized storage & handling |
Rule of thumb: TDS (mg/L) ≈ 0.5–0.7 × conductivity (µS/cm). Devices that list a max conductivity or max TDS are asking for low-mineral water regardless of method.
Uses & Applications
Distilled water’s near-zero minerals prevent scale, spots, and residue—ideal for appliances, lab/cosmetic prep, and certain automotive tasks. For drinking, many people prefer mineral or filtered water for taste (or lightly remineralize).
Common Use-Cases
- CPAP & Humidifiers: Prevents mineral scale and airborne white dust. Empty & dry reservoir daily.
- Steam Irons & Clothes Steamers: No mineral spots on fabrics; descale less often.
- Glass/Surface Steamers: Reduces streaking and nozzle clogging.
- Lead-Acid Batteries: Top-up with distilled only (to plates’ level). Follow vehicle/manual guidance.
- Coolant Mix (Automotive): Many OEMs recommend demineralized/distilled for mixing with concentrate—check your manual.
- Espresso/Autoclave Rinse: Use for rinse cycles or after descaling to avoid new deposits. (Brew water usually needs minerals for taste & corrosion balance.)
- Cosmetics/Skincare DIY: Use distilled in water-based formulas; store in sanitized containers.
- Lab/Instrument Rinse: Low residue for glassware and electrodes; verify required grade (conductivity/TDS).
- Aquariums/Plants: Mix with salts/buffers to target GH/KH; do not use plain distilled for tanks or hydroponics.
Do / Don’t
- Do: Store in clean, sealed glass/HDPE away from heat/sunlight; label date opened.
- Do: Check equipment manuals for “distilled,” “demineralized,” or “purified” requirements.
- Don’t: Leave water sitting in warm tanks (biofilm risk); refresh routinely.
- Don’t: Use plain distilled where minerals are required (brewing, aquaria, some espresso profiles) without remineralizing.
Safety note: For medical devices (e.g., CPAP), follow manufacturer instructions for cleaning and replacement intervals.
Health & Safety
Distilled water is very low in minerals and tastes flat. It’s generally safe to drink, but it isn’t required for most people and isn’t the best choice in some scenarios. Use this section as practical, non-medical guidance.
Drinking & Electrolytes
- Taste: With near-zero TDS, distilled tastes neutral/flat. Many people prefer mineral or filtered water for daily drinking.
- Mineral intake: Minerals primarily come from food. If using distilled as your main water, you can add trace minerals or a pinch of bicarbonate/magnesium blend for taste (optional).
- After sweating/illness: Hydration may also require electrolytes (Na/K). Consider foods (soups, salted snacks, fruit) or an electrolyte beverage if appropriate.
- Myth check: Distilled water doesn’t “pull minerals” out of you in a meaningful way during normal diets; the body regulates electrolytes tightly. Still, don’t rely on any plain water to replace heavy electrolyte losses.
Infants, Pregnancy & Medical Contexts
- Infant formula: Use water type and preparation steps exactly as the formula label or clinician directs (some advise boiled/cooled water; some allow distilled).
- Medical devices: Devices like CPAP/humidifiers often require distilled to prevent scale. Follow cleaning and replacement schedules.
- Clinician advice: If you have kidney, heart, or electrolyte disorders—or are on sodium/potassium restrictions—ask your clinician what water fits your plan.
Reminder: This is informational, not medical advice. Follow device manuals and your healthcare provider’s guidance.
DIY Distillation & Storage
Choose a countertop distiller for set-and-forget consistency, or use a careful stovetop setup. Expect low output per hour and some energy cost; clean and store properly for best results.
Method A — Countertop Distiller
- Prep: Rinse boiler and collection jug. Install/replace the small carbon sachet if your unit uses one.
- Fill: Add tap/filtered water to the MAX line (do not exceed).
- Run: Assemble lid/fan. Start cycle. Typical batch: 3–6 hours for ~3–4 L (varies by model).
- Collect: Distillate flows into a clean glass or HDPE jug. Cap immediately after cooling.
- Descale: After each batch or when you see scale, soak boiler with warm citric acid or white vinegar; rinse thoroughly.
Tip: If output tastes “flat” or plasticky, flush a short batch and discard, ensure the carbon sachet is fresh, and store in glass.
Energy Cost per Liter (Estimator)
E-E-A-T: Home methods are for producing low-mineral water for appliances and general use. They do not create sterile water for medical procedures. Follow device manuals.
Remineralization & Taste
Distilled water is ultra-low mineral. To improve taste—or meet equipment recipes (coffee/tea)—add a small amount of alkalinity and hardness. Use food-grade ingredients, measure carefully, or choose commercial mineral drops.
Taste Targets (Everyday Drinking)
| Profile | Approx. Targets | Simple Adds (per 1 L) |
|---|---|---|
| Crisp/Neutral | TDS ~60–90; Alk 20–35; Hardness 10–30 (as CaCO₃) | NaHCO₃ (baking soda) ~0.04–0.06 g ➜ +Alkalinity MgSO₄·7H₂O (Epsom) ~0.02–0.05 g ➜ +Mg hardness |
| Balanced | TDS ~90–130; Alk 30–50; Hardness 30–60 | NaHCO₃ ~0.06–0.08 g + MgSO₄·7H₂O ~0.05–0.08 g |
| Filter Coffee / Tea (general) | TDS ~70–120; Alk 30–50; Hardness 30–60 | Start with the Balanced row; adjust by taste/equipment guidance. |
Food-grade only. Weigh small amounts with a 0.01 g scale. If you’re sodium-restricted, use potassium bicarbonate (KHCO₃) instead of NaHCO₃—ask your clinician if unsure.
“No Tiny Weighing” Method — Make Concentrates
- Alkalinity concentrate: Dissolve 1.00 g baking soda (NaHCO₃) in 1 L clean water. Add 50 mL of this concentrate to 1 L distilled water → ≈ 30 mg/L alkalinity (as CaCO₃).
- Magnesium concentrate: Dissolve 10.0 g Epsom salt (MgSO₄·7H₂O) in 1 L. Add 5 mL to 1 L distilled → ≈ 20 mg/L hardness (as CaCO₃).
- Tip: Label bottles and refrigerate concentrates. Shake before dosing; use clean syringes/spoons.
Faster option: Mineral-drop products and remineralization cartridges set targets without math—follow the label for TDS/alkalinity.
DIY & FAQs
Quick checks, clear answers, and fixes for the most common distilled-water questions—from “is boiling the same?” to humidifier white dust.
Quick Checks
- Verify purity: Rinse a clean cup, pour sample, measure with a simple TDS meter. Target ≤ 10 mg/L for fresh distillate.
- Smell/taste off? Flush your countertop distiller, replace the small carbon sachet (if used), and store output in glass or HDPE.
- Scaling boiler: Soak with warm citric acid or vinegar, then rinse thoroughly before next run.
- Storage: Cap tightly, store cool/dark. For devices (CPAP/humidifiers), use fresh water daily.
- Equipment wording: “Distilled,” “Demineralized,” or “Purified” in manuals generally means low-TDS water—match the spec if given.
Mini How-To: Clean a Humidifier Tank
- Empty the tank; fill with warm water + a splash of white vinegar (per manual).
- Soak 20–30 minutes; gently brush crevices; rinse well.
- Air-dry parts; refill with distilled; replace wicks/filters as scheduled.
Tip: If white dust persists with distilled water, check for mineral residue inside the device or high room dust; clean more often.
Written by Alex Bennett
About the Author
Alex Bennett is a U.S.-based writer focused on sparkling and mineral waters, flavor trends, and home carbonation. Reviews prioritize ingredient transparency, mineral specs (TDS/µS·cm), and real-world use cases (daily sipping vs. cocktail mixers).
- Experience: 5+ years tasting and comparing seltzers and mineral waters.
- Method: Blind tastings (chilled & over ice), label checks for sodium/TDS, and use-case scoring.
- Editorial policy: No paid placements; products purchased or disclosed if sampled.
Transparency: We recommend unsweetened options for daily sipping and advise checking labels for sodium and acids. This guide is informational—not medical advice.