Both codes mean "water jets from any direction," and the difference is one line in the test table. IP65 is a 6.3 mm nozzle delivering 12.5 L/min from 3 m away; IP66 is a 12.5 mm nozzle delivering 100 L/min from the same 3 m. That is eight times the water and roughly three times the pressure at the nozzle. If the enclosure passes IP66 it passes IP65; the reverse is not true. Ratings quoted here are manufacturer ratings — rated NEMA 4X / IP66 by the manufacturer; not UL listed — and the same rule applies to any IP mark you see on a box.
What each digit of the code means
The first digit is solids, the second is water. The "6" in IP6X means dust-tight: no ingress of dust in the dust test. That is why IP65 and IP66 sit at the same level as a NEMA 4X box for dust, and why they are the two codes you see on stainless wall-mount enclosures for washdown plants.
The second digit is where the two part ways. IPX5 is "protected against jets," IPX6 "protected against powerful jets." Those words are defined entirely by the test apparatus in IEC 60529 — nozzle bore, flow, distance, time — not by any adjective. For the full digit chart and how each level is tested, read the IP rating chart.
The water jet tests, number by number
IEC 60529 defines both tests with the same skeleton: a clean-water jet from a spray nozzle, aimed at every part of the enclosure, from a set distance, for a set time. What changes between IPX5 and IPX6 is the nozzle and the flow.
| Parameter | IP65 (IPX5 jet) | IP66 (IPX6 jet) |
|---|---|---|
| Nozzle bore | 6.3 mm (0.25 in) | 12.5 mm (0.49 in) |
| Water flow | 12.5 L/min (3.3 gal/min) | 100 L/min (26.4 gal/min) |
| Pressure at nozzle | about 30 kPa (4.4 psi) | about 100 kPa (14.5 psi) |
| Distance to enclosure | 3 m (9.8 ft) | 3 m (9.8 ft) |
| Test time | 1 min per m², at least 3 min | 1 min per m², at least 3 min |
| Jet direction | all directions | all directions |
Two points worth fixing in mind. First, the pressure column is the water pressure at the nozzle, delivered by the test rig so the flow rate comes out right; the standard does not specify a supply pressure. Second, test time scales with surface area, so a small junction box gets the 3-minute minimum while a 48 x 36 x 8 in cabinet is sprayed longer, surface by surface.
Why people ask about pressure, and what the answer is
Plant people think in hose pressure because that is what a gauge on a washdown station reads. The test thinks in flow through a known bore, which is why pressure alone cannot settle IP65 versus IP66. A pressure washer at 100 bar through a pencil jet may move less than 12.5 L/min — less water per second than the IP65 test — while a 100 L/min deluge at low supply pressure hits far harder in total water.
If you must compare, convert your washdown station to nozzle bore and flow: a 12.5 mm nozzle at about 100 L/min aimed at the enclosure from 3 m is the IP66 condition. Anything at or below that, IP66 is the right call. Anything above it — dedicated high-pressure washers, close-range foam-and-rinse stations — belongs to a bigger discussion: NEMA 4X vs 4X hose-down practice and, for submersion or prolonged flooding, the immersion types covered in NEMA enclosure types explained.
What is tested and what is not
The IP jet tests spray water at the enclosure as delivered by the manufacturer: closed, latched, with its own glands or blanking plugs in place. They do not test a door you propped open, a field-drilled hole, a cheap cable gland, or a window someone cut on site. Any penetration you add after delivery is your responsibility to seal to the same level — see installing a cable gland without losing the rating for how quickly a wrong gland defeats a good box.
The jet tests also say nothing about:
- Corrosion. That is a separate test; in the NEMA world it is what separates Type 4X from Type 4, an added salt-spray exposure. An IP66 mark alone tells you nothing about the material's rust resistance.
- Immersion. IPX7 and IPX8 are different tests in still water at depth, not stronger jets.
- Ice, sleet or external icing, covered by some NEMA types.
- Knock, impact or gasket aging.
For the difference between Type 4 and Type 4X on the corrosion side, see NEMA 4 vs 4X vs IP66.
Why NEMA-to-IP conversion charts contradict each other
Charts disagree because neither system is a subset of the other. IEC 60529 jet tests and the NEMA 250 / UL 50E hose tests use different apparatus, flow rates and durations, so "equivalent" is always an approximation. NEMA types also include requirements IP codes never touch — corrosion for 4X, icing for outdoor types — while IP codes include dust and immersion levels NEMA does not map cleanly. A chart author picks which differences to ignore, and different authors ignore different ones.
In US installations the Code settles the argument: NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings. If the plant spec calls for a NEMA type, mark the NEMA type; carrying both marks, as our boxes do, satisfies both audiences. And note what a mark means: a manufacturer rating is a declaration against the standard, not a certification — what a UL listing adds is covered in UL 50E vs NEMA 250: listed or manufacturer-rated?.
Which code to write on the order
For a hose-washdown area — food plant, beverage, any rinse-down station — specify IP66 minimum, and in North America specify NEMA 4X, which is the type the plant's inspectors will look for. Choose 316L stainless where the rinse carries chlorides or cleaning chemicals, as most food plants do; 316L wall-mount enclosures cover that. IP65 is adequate for indoor jets that are light rinse rather than washdown: a 12 x 12 x 6 in junction box by a wipe-down hose, for example. A deeper run-through of choosing by environment is in outdoor enclosures: sun, rain, ice and the right rating.
If you are comparing a washdown spec that mixes the terms, washdown rating versus NEMA 4X versus IP65 lines the three vocabularies up against each other.
What to specify, in one block
- Rating wording: NEMA 4X / IP66 (IP65 only for light rinse areas).
- Material: 316L for chloride washdown, 304 for general hose-down indoors.
- Mounting: hinged gasketed door, removable panel, glands on a gland plate rather than holes in the body.
- Anything you drill later: sealed with rated glands or plugs, never left open.
Our stainless enclosures are rated NEMA 4X / IP66 by the manufacturer; not UL listed, and delivered in 10 business days from your order — from your approval of the drawing for custom work. Options include the 12 x 12 x 6 in 316L box and the 16 x 16 x 8 in 316L box.
Enclosures in this article
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 12 × 12 × 6 in | 316L stainless | 12 x 12 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 16 × 8 in | 316L stainless | 16 x 16 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Is there an official water pressure for IP65 and IP66 jets?
Not as a supply pressure. IEC 60529 sets the water delivery at the nozzle: approximately 30 kPa (4.4 psi) for IP65 through a 6.3 mm nozzle at 12.5 L/min, and approximately 100 kPa (14.5 psi) for IP66 through a 12.5 mm nozzle at 100 L/min. The nozzle geometry, flow rate and 3 m distance define the jet; the pressure at the nozzle follows from those numbers.
If an enclosure meets IP66, does it also meet IP65?
Yes. IP66 is the harder test: bigger nozzle, eight times the flow, roughly three times the pressure at the nozzle, from the same 3 m distance. Anything that keeps that jet out also keeps the smaller IP65 jet out. The reverse does not hold, which is why a washdown area is usually specified as IP66 minimum.
Why do NEMA to IP conversion charts disagree?
Because the test families are different. IEC 60529 tests water jets and temporary immersion with defined nozzles; NEMA 250 and UL 50E hose tests use their own nozzle, flow and duration, and add tests IP codes do not have, such as corrosion for Type 4X. Charts are approximations, and in US installations NEC 110.28 says IP ratings are not a substitute for enclosure type ratings. Ask for both marks when you need both.
Can I convert a hose pressure at my plant to an IP test?
Not directly. The standard does not name a supply pressure, so a plant hose at high pressure but low flow through a small nozzle may hit less water per second than the IP66 jet. Compare nozzle diameter and flow rate instead: roughly 100 L/min through a 12.5 mm opening at 3 m is what IP66 represents. If your washdown nozzles exceed that, look at the NEMA 4X hose test or immersion-rated types.
