Deionized vs Distilled Water: Which One Cleans Better?
Deionized vs distilled water: how each is made, where each wins, and which one gives streak-free glass, facades and solar panels on South Florida buildings.
Both are “pure” water, and for exterior cleaning the practical difference is small. Distilled water is boiled into steam and condensed again. Deionized (DI) water is passed through ion-exchange resin that strips out dissolved minerals. For glass, facades and solar arrays, DI is usually the better working choice because it is fast and cheap to produce at volume. Distilled is a fine alternative when a job is small or you have no DI system. If you manage a building in Miami, Fort Lauderdale or Boca Raton, what matters more than the label is how the water is made, filtered, stored and delivered on the day.
Below we cover how each type is made, where each belongs (lab, medical, cleaning), and what the choice means for window, facade and solar work in South Florida’s salt air, heat and humidity.
TL; DR
- Distilled water is made by boiling and recondensing. Deionized water is made by ion exchange. Both leave very few dissolved minerals, which is why both dry without spots.
- For commercial cleaning volumes, DI is the practical choice: the EPA’s WaterSense guidance notes that distillation takes far more energy and time than deionization.
- Neither is a drinking-water product or sterile water. Do not swap either one in for medical use.
- DI water is aggressive: it picks up minerals and CO2 quickly, so it should be made close to where it is used and filtered at the output.
- On anodized aluminum, powder-coated metal and other finishes, pure water is the gentle part of the process. The coating maker’s care guidance still decides what else touches the surface.
Table of Contents
- How each type of water is made
- Deionized vs distilled at a glance
- Why spots happen, and why pure water avoids them
- Pure water and electricity: a common worry
- Where DI water goes wrong
- What about drinking, plants and medical equipment?
- Anodized aluminum, powder coat and other finishes
- Which water suits which exterior job
- How to vet a cleaner’s water claims
- Our perspective: purity is a process, not a label
- What this means for your building
- FAQ
- Sources
How each type of water is made
Distilled water starts as ordinary water that is heated to steam. The steam leaves most solids and minerals behind, then cools and condenses into a separate container. The process also leaves behind many organic contaminants, and the EPA’s water purification guide describes it as energy and time intensive.
Deionized water is made by forcing water through ion-exchange resin. Tap water carries charged particles from the soil and from pipes, such as sodium, calcium, iron and copper. The resin swaps those for hydrogen and hydroxide ions, which combine into plain water. The University of Illinois Physics Van gives a plain explanation of this: DI water is simply water with the ions taken out.
That last point is the key limit. Ion exchange targets ions. It does not reliably remove bacteria, viruses or many organic compounds, while distillation does a better job on those. For a window, that rarely matters. For a medical device, it matters a lot.
Deionized vs distilled at a glance
| Factor | Distilled | Deionized (DI) |
|---|---|---|
| How it is made | Boiling, then condensing steam | Ion-exchange resin |
| Removes dissolved minerals | Yes | Yes |
| Removes microbes and organics | Largely, through the process | Not reliably |
| Speed and energy | Slow, energy-heavy | Fast, lower energy |
| Practical at commercial volume | Costly | Yes |
| Best fit | Small batches, sensitive uses | High-volume cleaning, lab rinses |
| Main watch-out | Can pick up microbes if stored badly | Absorbs CO2 and minerals if stored; resin residue if unfiltered |
The real answer to “which is purer” depends on what you measure. Mineral content: both are very low. Microbial and organic content: distilled has the edge. Cost and volume: DI wins. For rinsing glass and panels, the mineral content is the only number that decides whether a surface dries clean.
Why spots happen, and why pure water avoids them
When ordinary water evaporates from glass, the dissolved minerals stay behind as a white film. Pure water leaves nothing to stay behind. That is the whole principle behind streak-free glass and solar cleaning.
A UNLV thesis on soiling removal from photovoltaic panels notes that solar facilities where soiling is a problem use demineralized water, and it tested how lower-quality water performs against purer water on panels. Distilled water did better on the soiling it tested than the lower-quality types. The practical lesson is the same for a glass curtain wall: the less the water carries, the less it leaves.
South Florida makes the risk higher. Heat dries water quickly, humidity and salt-heavy air deposit more grime, and the research we reviewed points to mineral scaling that traps dirt and bonds to the surface, making each later cleaning harder and more expensive. If you want the property-manager version of this story, our guides on why high-rise windows streak after rain and streak-free high-rise glass cleaning steps go deeper.
Pure water and electricity: a common worry
Property managers often ask whether spraying water near solar arrays or rooftop electrical gear is safe. The USGS explains that conductivity depends on dissolved ions, and that pure water is a poor conductor. That is one reason both distilled and DI water are preferred around sensitive equipment.
Two cautions belong right next to that fact. First, water does not stay pure once it touches a dirty surface, because it dissolves what it lands on. Second, a spray pattern aimed at live equipment is a different question from the water’s purity. Follow the array manufacturer’s cleaning instructions, and ask your electrician or system installer about any exposed connections before work starts.
Where DI water goes wrong
DI water is not a “set and forget” product. Three habits separate clean results from disappointing ones.
- Use it near the point of production. According to the EPA guidance, stripped water seeks to rebalance itself and absorbs CO2 and minerals from its surroundings, including from storage containers. Leaving it in an open or plastic tank for days undoes the purification.
- Filter the output. Simple resin columns can release small amounts of resin beads or residue. A USGS memorandum on distilled and deionized water for district operations covers quality requirements for this kind of water, and practitioners commonly add a fine final filter, often 0.45 micron, so the water coming out is truly clean.
- Maintain the resin. The EPA notes that efficiency improves when resin is regenerated based on volume or conductivity rather than on a fixed calendar schedule. A water-quality meter at the outlet tells you when to swap, so you are not guessing.
The same logic applies to distilled water: it is only as good as the container it is delivered in. If a crew fills a dirty tank with it, you have bought expensive tap water.
What about drinking, plants and medical equipment?
The search results for this topic mix cleaning, lab and household questions, so a short, careful answer is worth giving.
- Drinking. Neither type is intended as a primary drinking-water source, and neither is guaranteed sterile. The CDC’s page on tap water contaminants lists distillation and reverse osmosis among treatments recognized for removing Cryptosporidium. If someone in your household or building has a weakened immune system, ask their doctor or your local water utility what water they should use.
- Medical devices. Distilled is not the same as sterile. A CDC study in Emerging Infectious Diseases looked at how people misunderstand unsterile water in home medical devices, and it names older adults, young children and people with weakened immune systems as being at higher risk of infection. For a CPAP, nebulizer or similar device, follow the maker’s label and your clinician’s advice, which may call for sterile water.
- Plants. We keep our advice to the building side of the fence here. Pure water also lacks the minerals plants normally get, so ask a landscaper or your extension office before using it on green walls or landscaping.
Anodized aluminum, powder coat and other finishes
Many of the building owners we talk to ask this on the same day they ask about water. The finish decides how careful the whole process must be, and water is the lowest-risk part.
Anodized aluminum is a finish formed from the metal itself through an electrochemical process. Powder coating is a separate layer of cured powder applied over the metal. They look similar from the street, but they respond differently to harsh chemicals, abrasion and aggressive cleaners. The shared rule is simple: use a pure-water rinse, a mild neutral cleaner when one is needed, a soft touch, and never a strong acid or alkaline product unless the coating manufacturer approves it.
We do not publish a spec table here because the right product depends on your finish, its age and its warranty. Check three things before any cleaning:
- The coating’s care guidance. Your architect, window-wall supplier or coating applicator should be able to give you the maintenance instructions.
- Your warranty terms. Some warranties require a stated cleaning frequency or method.
- A test patch. Clean a small, low-visibility area first and check it in daylight once dry.
On stucco, EIFS, concrete, tile and metal, we pair a pure-water rinse with substrate-matched soft-wash chemistry rather than a single approach. You can see how this looks on a real job in our video on drone cleaning metal sun-shade louvers, and our facade cleaning page lists the substrates we handle.
Which water suits which exterior job
| Surface | Preferred approach | Why |
|---|---|---|
| High-rise glass | Pure-water rinse, DI or distilled | Dries without mineral film |
| Solar panels | Pure-water wash, no residue | Avoids scaling that traps dirt on the glass |
| Anodized or powder-coated metal | Pure-water rinse plus mild cleaner if needed | Gentle on the finish |
| Stucco, EIFS, concrete | Soft-wash chemistry, then pure-water rinse | Chemistry is matched to the substrate |
| Roofs (tile, metal) | Soft-wash, rinse as the roof requires | Cleaning, not spot control, is the goal |
For most commercial projects, the water is produced as DI on site or nearby, because a 30-story curtain wall uses far more water than a distiller can produce at a reasonable cost. That is the same reason the EPA’s guidance favors deionization over distillation for facilities that need volume.
How to vet a cleaner’s water claims
If a vendor says they use pure water, a risk manager or facilities director can ask five short questions.
- How is the water produced, by DI, distillation or reverse osmosis?
- How do you verify purity on site, and with what meter?
- Is there a final filter at the outlet?
- How long is the water stored before use, and in what kind of tank?
- Do you document results, for example with before-and-after photos?
A vendor who answers these without hesitation has thought about the process. Equally useful is the cleaning side: the water is only part of an overall method. A good vendor will also explain access, insurance and how they protect fixtures. For a helpful comparison of the other end of the spectrum, an office-focused guide on glass partition cleaning steps that protect office hardware shows how much a careful method matters to the finish of glass at close range.
Our perspective: purity is a process, not a label
We clean high-rise windows, facades, roofs and solar arrays across Miami-Dade, Broward and Palm Beach counties from the ground, using tethered industrial drones flown by FAA Part 107-certified pilots. Water purity sits at the center of the results we deliver, so we get asked about this a lot.
Our view is simple. Customers do not need to choose a side in the DI versus distilled debate. They need a crew that treats pure water as a controlled input: produced fresh, filtered at the outlet, delivered through clean lines, and rinsed on the surface the right way. On a building near Biscayne Bay or the Atlantic, salt, humidity and heat will punish shortcuts within weeks, because minerals bond to the surface and later cleaning becomes harder.
We also think the surface matters as much as the water. A glass curtain wall, a stucco facade, an anodized frame and a solar module do not want the same treatment. Our process uses a pure-water rinse across the board and substrate-matched soft-wash chemistry where the material needs it. Every job is photographed in 4K before and after, so you can see the result and check it against your own standards.
And we think the safest way to do this work is with nobody hanging off the side of the building. That is the reason our crews stay on the ground, without scaffolding, boom lifts or rope access.
Eliot
What this means for your building
Our drone cleaning service is built around pure-water rinsing. Window cleaning is priced from $0.12 to $0.25 per sq ft of glass, and facade and building cleaning is priced at $0.12 to $0.25 per sq ft. Solar panel cleaning runs $1 to $3 per panel, and parking garage cleaning is $0.06 to $0.08 per sq ft. Roof and industrial cleaning are quoted per project. Final pricing depends on building area and service type, and quotes are free.
Start with the page that matches your building:
- Drone window cleaning for high-rise glass.
- Drone facade and building cleaning for stucco, concrete, EIFS, metal and tile.
- Drone solar panel cleaning for rooftop arrays, with a detailed explainer on how the process works.
If you would rather talk it through, send us the building details and we will reply with a free quote within 24 hours.
FAQ
Is deionized water the same as distilled water?
No. Distilled water is made by boiling and condensing water, and deionized water is made by passing it through ion-exchange resin. Both have very few dissolved minerals. Distillation also tends to remove more microbes and organics, while deionization is faster and cheaper at volume.
Which is better for cleaning windows and solar panels?
Either works, because both leave almost nothing behind when they dry. DI is usually the practical choice for commercial work, since it can be produced in the volumes a tall building needs. The main condition is that it is fresh and filtered at the outlet.
Can I drink deionized or distilled water?
Neither is meant to be a primary drinking source, and neither is guaranteed sterile. If you have a weakened immune system or are choosing water for a medical device, ask your doctor or the device maker. They may recommend sterile water rather than distilled.
Can I make DI or distilled water myself for building cleaning?
For a few windows, a small resin cartridge system or bought distilled water will do. For a high-rise, the volume makes DIY impractical, and storage matters because DI water absorbs CO2 and minerals when left standing. Commercial projects are best handled by a crew with a dedicated, filtered system.
Will pure water damage anodized aluminum or powder coat?
Pure water itself is gentle on both finishes. The risk comes from harsh cleaners and abrasion, so check the coating manufacturer’s care guidance and your warranty, and test a small area first.
Sources
- WaterSense at Work, Section 7.1: Water Purification (EPA)
- What is Deionized Water? (Physics Van, University of Illinois)
- The Impact of Waters of Low Quality on Soiling Removal from Photovoltaic Panels (UNLV)
- Conductivity (Electrical Conductance) and Water (USGS)
- Distilled/Deionized Water for District Operations (USGS)
- Chemicals That Can Contaminate Tap Water (CDC)
- Misperception and Use of Unsterile Water in Home Medical Devices (CDC, Emerging Infectious Diseases)