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The short answer
The best substitute for distilled water depends on the job. For a neti pot, boiled-and-cooled tap water or a filter certified for cyst reduction works (FDA). For humidifiers, reverse osmosis or deionized water is the closest match (EPA). For steam irons, many makers want plain tap water. For a CPAP or contact lenses, follow the manufacturer: some CPAP makers say distilled only, and lenses need sterile solution. Purified water labeled as made by reverse osmosis or deionization is a close substitute for most appliance uses.
Is distilled water the same as purified water?
Not exactly. Under FDA rules, “purified water” is water made by distillation, deionization, reverse osmosis, or other suitable processes that meets the US Pharmacopeia standard. It may be labeled “distilled water” only if it was distilled, “deionized water” if deionized, and “reverse osmosis water” if made by RO. So all distilled water is purified water, but a bottle labeled “purified” may be RO or deionized. The EPA says distillation removes minerals most effectively, and water demineralized by deionization or RO would, on average, be expected to contain a higher mineral content. Our reverse osmosis vs distilled water guide compares the two in more detail.
| Label | What it means (21 CFR 165.110) |
|---|---|
| Purified / demineralized | Made by distillation, deionization, RO, or similar; meets the USP purified water standard |
| Distilled | Purified water made by distillation |
| Sterile | Passes USP sterility tests; the only label that guarantees sterility |
| Spring | From an underground source; minerals not removed |
| Mineral | At least 250 ppm total dissolved solids, the opposite of distilled |
Distilled isn’t the same as sterile. The FDA treats “sterile water” as a separate label (21 CFR 165.110).
What can you use instead of distilled water?
| Use | Best | Acceptable substitute | Avoid |
|---|---|---|---|
| Neti pot | Distilled or sterile | Tap water boiled 3 to 5 minutes and cooled (FDA); a filter certified for cyst reduction | Untreated tap water |
| CPAP humidifier | Distilled | Tap water only if your maker allows it; ResMed does but recommends distilled (ResMed) | Additives; Philips says distilled only (Philips) |
| Ultrasonic humidifier | Distilled | RO or deionized water (EPA) | Spring or mineral water |
| Steam iron (Rowenta) | Untreated tap water | 50/50 tap and distilled if your water is very hard (Rowenta) | Pure distilled, filtered, or rainwater |
| Lead-acid battery | Distilled | Deionized, if necessary (Trojan) | Tap or mineral water |
| Baby formula | Safe tap or bottled water | Low-fluoride bottled water, if you want to lower fluorosis risk (CDC) | Water under a local warning |
| Contact lenses | Sterile commercial solution | None | Any water, distilled included (CDC) |
What water is safe for a neti pot?
The FDA says use distilled or sterile water, tap water boiled for 3 to 5 minutes and cooled until lukewarm, or water passed through a filter designed to trap infectious organisms. Boiled water keeps in a clean, closed container for 24 hours (FDA). The CDC says a 1-minute rolling boil, or 3 minutes above 6,500 feet (CDC). For filters, the CDC lists those certified to NSF/ANSI 53 or 58 for cyst reduction or with an absolute pore size of 1 micron or smaller. Most pitcher filters don’t carry a cyst claim.
What can you use instead of distilled water in a CPAP?
Check your machine’s manual first. The Philips DreamStation humidifier manual says to use only room temperature distilled water with no additives. ResMed says tap water can be used but recommends distilled water to limit mineral buildup. Bottled purified water made by RO is the nearest substitute where your maker allows it.
What water should you use in a humidifier?
The EPA recommends water with low mineral content, such as distilled water, because ultrasonic and impeller humidifiers spray minerals into the air as white dust. Water demineralized by RO or deionization is the next best option. Spring, artesian, and mineral bottled waters haven’t had their minerals removed. Even distilled water still contains some minerals, the EPA notes.
Do you need distilled water for baby formula?
No. The CDC says to use water from a safe source, and that bottled water is safe to use (CDC). For babies younger than 2 months, born prematurely, or with a weakened immune system, it advises boiling the water first. Formula made with fluoridated water may increase the chance of mild dental fluorosis; bottled water labeled deionized, purified, demineralized, or distilled has no or only trace amounts of fluoride. See the best water for baby formula.
Can you make distilled-quality water at home?
A countertop distiller makes true distilled water, slowly. A reverse osmosis system makes water that’s close for most uses: NSF/ANSI 58 requires at least 75% TDS reduction, and certified systems often do better. A pitcher filter doesn’t lower minerals much and isn’t a substitute.
| # | System | Score | Certified by | Lead | PFAS | Fluoride | Running cost | Price |
|---|---|---|---|---|---|---|---|---|
| 01 | AquaTru CarafeCountertop RO, no plumbingCountertop RO | 4.6 | IAPMO R&T | Certified | Certified | Certified | $0.33/gal | $335.75on Amazon › |
| 02 | Waterdrop G3P800Tankless under-sink ROUnder-sink RO | 4.3 | IAPMO R&T | Certified | Certified | Certified | About $160/yr | $759.00on Amazon › |
| 03 | APEC RO-90Under-sink RO with tankUnder-sink RO | 4.2 | WQA | Certified | No | Certified | $60 to $75/yr | $209.99on Amazon › |
Certified: Certified by an independent body (named in each pick). Lab test: Tested by a named independent lab, not certified. Claim: The maker's claim, not certified. No: No claim. PFAS means PFOA/PFOS, or Total PFAS where the pick says so.
Common questions
Is distilled water the same as purified water?
Not exactly. Purified water can be made by distillation, deionization, or RO; it’s called distilled only if it was distilled (21 CFR 165.110).
Can I use purified water instead of distilled?
For most appliances, yes, though RO or deionized water has slightly more minerals on average than distilled, according to the EPA. Follow your appliance’s manual for CPAPs.
Can I use boiled water instead of distilled water?
For a neti pot, yes: the FDA says boil 3 to 5 minutes and cool. Boiling doesn’t remove minerals, so it won’t stop scale or white dust.
Is distilled water sterile?
Not necessarily. The FDA treats sterile water as a separate label. For contact lenses, use only sterile solution (CDC).
Can I use filtered water instead of distilled?
A pitcher filter doesn’t remove many minerals, so not for humidifiers or CPAPs. RO water is a close substitute. For a neti pot, only a filter certified for cyst reduction or with 1-micron absolute pores.
Sources
Prices as of November 1, 2026. Product prices and availability are accurate as of the date/time indicated and are subject to change. As an Amazon Associate we earn from qualifying purchases.