Cable glands on a submerged enclosure: route 10 cables dry

Short answer: one gland per cable, each one rated by its datasheet for the actual depth and run time, mounted on an enclosure that itself carries an immersion rating - Type 6P, the type for prolonged submersion. A Type 4X / IP66 box handles hose jets and rain; it has no immersion rating, so it is the wrong enclosure under water. The worked case through this article: a small pump controller with ten cables - eight signal cables at 6 mm OD, two power cables at 10 mm OD - sitting 2 m down for 21 days at a time in fresh water. You get the ratings to order, the gland sizes and hole diameters, and the bench test that proves the assembly before it dives.

Which enclosure rating survives continuous submersion?

A box that lives under water needs Type 6P - the NEMA type for prolonged submersion, whose nearest IP code is IP68 - and the manufacturer's stated test depth and duration; a Type 4X / IP66 enclosure covers hose-directed water and rain only.

NEMA 250 draws the line cleanly: Type 6 covers temporary submersion and its nearest IP match is IP67 (1 m for 30 min); Type 6P covers prolonged submersion and matches IP68. IEC 60529 leaves the second digit 8 open - continuous immersion under conditions agreed between manufacturer and user - so the depth and the minutes live in the datasheet, beside the code. In US installations, NEC 110.28 states that an IP code alone does not stand in for an enclosure type rating, so a submerged-build spec carries the type and the numbers.

Material follows the water. 304 stainless suits fresh water; salt, brine or chlorinated water takes 316L. Temperature has a flag too: about 60 °C (140 °F) is the chloride stress-corrosion threshold for both grades, so warm chlorinated water is a 316L conversation. Our stock stainless boxes are rated NEMA 4X / IP66 by the manufacturer; not UL listed - a wet-location rating, not an immersion one. A box that will live under water starts as a custom Type 6P build: state depth, duration, fluid, temperature and the number of penetrations, and the design answers them (custom enclosures). For what each rating is tested against, see the NEMA 4 vs 4X vs IP66 guide and the continuous immersion article.

Can you keep the box out of the water instead?

Yes - mounting the enclosure above the waterline and running one submersible-rated cable down to the pump turns ten underwater penetrations into one, and that single cable still needs a gland whose datasheet covers the depth.

Every penetration is a leak path, and depth multiplies what each path must hold. The dry-box layout keeps the controller, relay output and terminals serviceable at bench level, and only the pump cable enters the water. Size the drop properly: a 5 A pump at 12 V DC loses about 0.6 V over a 5 m run of 1.5 mm² (about 16 AWG) copper - 10 m of conductor at roughly 12 mΩ per metre, times 5 A. Longer runs or bigger pumps push you up a cable size. Feed the pump circuit through a 30 mA RCD, the IEC personal-protection level, so a wet-end fault trips instead of energizing the water.

If the pump disconnects for service, the entry becomes a connector question: a bulkhead gland arrangement keeps the enclosure penetration fixed while the cable comes off.

What does an IP68 gland rating actually promise?

Digit 8 of IEC 60529 sets no depth and no duration, so an IP68 gland promises exactly what its datasheet states - commonly 1 m for 30 min, which repeats the IPX7 condition, and better datasheets state more.

The code reads: first digit 6, dust-tight; second digit 8, continuous immersion under conditions agreed between manufacturer and user. A gland marked IP68 with no numbers is not a specification, so ask the maker to state depth and time on the datasheet or the order. Jets and immersion are different tests entirely - IEC 60529's second digit 6 uses powerful jets (12.5 mm nozzle, 100 L/min), which is why IP66 is not an immersion rating.

Two more rules bind the gland to the assembly. The weakest part sets the rating: an IP68 gland on a Type 4X / IP66 enclosure builds a Type 4X / IP66 assembly. And the gland's stated rating assumes its installation conditions - one round cable inside the clamping range, the maker's insert, the datasheet torque.

Worked example - does a catalog gland meet the duty? The box sits 2 m down for 21 days. Hydrostatic pressure there: 1000 kg/m³ × 9.81 m/s² × 2 m ≈ 19.6 kPa (0.20 bar, 2.8 psi). A gland stated at 1 m for 30 min is out of condition on both counts - the duty doubles the stated depth and asks 1008 times the stated duration (30,240 min ÷ 30 min). The order needs a gland the maker states at the working depth or deeper, for the full run time, in writing. The IP68 depth-and-time article explains how makers arrive at those numbers.

How do you size each gland to its cable?

Choose the gland whose datasheet clamping range holds the cable outer diameter near the middle: PG9 seals 4 to 8 mm OD, so a 6 mm signal cable sits mid-range, and PG13.5 seals 6 to 12 mm for a 10 mm power cable.

The ten-cable case, on typical datasheet clamping ranges and the standard PG drill sizes:

Mid-range is where the seal has rubber on both sides of the jacket; a cable at the range edge is the classic slow weep, so a 12 mm cable steps up to the next gland size. Measure the cable where it will be clamped, at build temperature: spiral wrap, an oversheath or a stiff cold jacket raises the effective OD. One round, intact jacket per gland does the sealing - two cables in one gland leaves a path (the two-cables article covers the above-water exception).

How do you route ten cables through a submerged box?

Ten cables mean ten glands, ten round holes and zero open spares, laid out so the bulkhead nuts clear each other and the door gasket - the sequence below takes the ten-cable controller from bare plate to sealed assembly.

You need: ten glands matched to the table above, the two drill sizes, a torque driver, blanking plugs at the same IP, a hand pump with a 0.2 bar gauge, soap solution, dry air and a desiccant pack.

1. Write the immersion envelope first: working depth of 2 m, 21 days continuous, fresh water, 4–30 °C. Every later choice reads off these four inputs; salt water, brine or anything above 60 °C changes the material and the seals.
2. Order the enclosure to the envelope as a custom Type 6P / IP68 build, stating all ten penetrations and their positions.
3. Pair every cable OD with a gland mid-range: eight PG9 for the 6 mm signal cables, two PG13.5 for the 10 mm power cables.
4. Put the holes in a removable gland plate rather than the box wall - 8 × 15.2 mm and 2 × 20.4 mm, deburred - so you can drill, fit and pressure-test the plate off the enclosure (gland plate article).
5. Fit each gland with the maker's serrated clamping insert and torque the compression nut to the datasheet value; anchor each cable close to its gland so pull loads bypass the seal.
6. Blank every unused hole with a plug stated at the same IP.
7. Purge the interior with dry air before closing and lay in a desiccant pack sized to the internal volume; trapped humid air condenses on the walls as the box cools at depth.
8. Pressure-test on the bench, then log the as-built: gland models with their stated depth and time, the torque, and the test result.

How do you check the assembly before it goes under?

Pressure-test the finished assembly at its working depth: the water bears 19.6 kPa (0.2 bar, 2.8 psi) on every seal there, so a 15-minute hold at that pressure with dry air finds a bad gland while the box is still on the bench.

Cap the glands or clamp them on the real cables, pressurize to 0.2 bar, and soap every gland and the door gasket: a growing bubble marks the leak. Pass is a steady gauge with no visible bubbles over the 15 minutes; any decay is a path to fix and re-test. In service, open the first inspection at one week, then monthly: a moisture film after a temperature swing points at a gland or the gasket, and the fix is re-torque plus fresh desiccant. An open drain hole would end the immersion rating, so moisture is managed with seals and desiccant, not a drain. Before any opening of a box that has been under water: isolate the supply and verify absence of voltage.

Which mistakes cost the rating?

The assembly rating falls to its weakest penetration, so each of these turns a rated build into a weeping one: a shared gland, an oversize hole, a gland stated below the duty, or sealant standing in for a rated entry.

• Two cables in one PG9 (4–8 mm range): the clamp seals a single round jacket, and the second cable rides outside it. One cable per gland at depth.
• A 16 mm hole under a 15.2 mm PG9 seal: the bulkhead seal needs its round, correctly sized hole; oversize holes call for a washer-faced gland, and a slotted hole has no seal at all.
• A 1 m / 30 min gland at a 2 m / 21-day site: outside the stated condition on depth and duration, however careful the installation.
• A Type 4X / IP66 box: its tests end at jets and rain, and submersion sits outside the rating.
• Hot glue or marine sealant as the only seal: sealant carries no stated depth, so treat it as armor over a rated gland; where there is no serviceable entry, a potted penetrator is the rated method (potting vs a rated enclosure).

What do you put on the order?

Order by case: a controller that lives under water goes out as a custom Type 6P / IP68 build with depth, run time, fluid and ten penetrations stated, while a dry-mounted box with a wet pump needs one immersion-rated gland and little else on the wet side.

• Box under water: a custom Type 6P / IP68 enclosure, 304 for fresh water or 316L for salt, brine and chlorinated water; penetrations listed as 8 × 15.2 mm and 2 × 20.4 mm; glands stated at the working depth or deeper, for the full 21-day duty. The underwater cable entry article compares glands, connectors and potted penetrators for that entry. We build these to the stated envelope, delivered in 10 business days from your drawing approval (custom enclosures).
• Pump under water, box dry: any correctly sized Type 4X wall-mount enclosure above the waterline - the enclosure selector sorts the stainless range by size and grade - plus one gland stated for the wet side.
• Sensor heads, no service entry: pot the leads; penetrations drop to zero and the box stays dry.

Catalog dimensions to compare

Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.

Questions