No. Distilled water and deionized water are two different products made two different ways, even though both end up very low in dissolved minerals. Distillation is a phase change; deionization is a chemical exchange on resin. Knowing which is which matters when a manual or a supplier specifies one of them by name.
Distillation: boil it and catch the steam
A distiller boils water and condenses the vapor in a separate chamber. Anything that will not evaporate at that temperature stays behind: dissolved calcium and magnesium, which the USGS describes as what water hardness is made of, plus sodium, metals, nitrates and any microorganisms present. That residue is exactly the scale you scrub out of the boiler. What can travel with the steam are volatile organic compounds boiling near water, which is why better distillers carry a carbon post-filter.
Deionization: swap the ions out on resin
Deionized water is made by passing water through cation and anion exchange resins that trade dissolved charged particles for hydrogen and hydroxide ions, which combine into water. It is very effective and very fast at removing anything carrying a charge. What it does not touch is anything uncharged: bacteria, many organic molecules, dissolved gases and particulates all pass through untouched, which is why deionization normally sits behind reverse osmosis and carbon rather than working alone.
So which is purer?
It depends on the contaminant. A deionizing bed can drive the mineral content lower than a single distillation, which is why it is used where conductivity must be extremely low. Distillation is stronger on the non-ionic side, since a phase change leaves bacteria, particulates and most heavy organics behind. Neither is universally purer, and industrial and laboratory water systems routinely use both in sequence rather than choosing. At home, distillation is the practical one.
Which does your application need?
Steam irons, humidifiers, CPAP machines and topping a lead-acid battery all name distilled water in their manuals, and distilled is what you should use. Laboratory work, some electronics rinsing and certain automotive coolant specifications call for deionized. Both are stripped of minerals, so where a device is protected simply against scale, either will serve; where a specification names one, treat that as the requirement. Our reverse osmosis system guide covers the home method closest to both.
Questions people ask about is distilled water deionized
Can I use deionized water in place of distilled water?
For scale prevention in appliances, generally yes. For anything where sterility or organics matter, distilled is the safer substitute of the two.
Is deionized water safe to drink?
It is not intended for drinking, since deionization does not remove bacteria or many organics. Do not treat a laboratory grade as a drinking supply.
Does a home distiller produce deionized water?
No. It produces distilled water. Deionization requires ion exchange resin, which is a different process with a different failure mode.
Which has a lower TDS reading, distilled or deionized?
Deionized water usually reads lower, because ion exchange targets exactly the charged species a conductivity meter responds to.