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Watertight seal test passed

Tubes and every penetrator hold a vacuum, then submerge dry.

0 of 9 steps0%
📦 materials: all 14 in hand
  1. 1check

    All sealing parts in hand

    Before assembling the pressure housing, make sure every sealing part and the vacuum-test kit are on the bench. A seal test fails fast if you are missing one blank or the grease.

    What good looks like

    1. Walk the Parts for this step list below (and the BOM) against what is on your bench: the tube, end caps, dome, O-ring flanges, clamps, penetrators and blanks, the vent / vacuum valve, the O-ring kit and grease, and the vacuum pump and plug.
    2. Every hole needs a plug. Count your penetrators and blanks — there must be enough to fill every cable hole you are not using. One open hole is a guaranteed leak.
    3. Have the leak sensors ready to drop inside for the dunk test.

    Done when

    Every sealing part and the vacuum kit are in hand. These are Phase-2 hull parts, so expect most to read to order until you source them.

  2. 2do

    Prep and grease the O-rings

    📦 all 2 in hand

    A clean, lightly greased O-ring in a clean groove is what actually keeps the water out. This is the step people rush and regret.

    Steps

    1. Clean every sealing surface: the O-ring grooves, the flange faces, and the inside of the tube where the O-rings ride. No grit, hair, or old grease.
    2. Inspect each O-ring for nicks, flat spots, or twists. A damaged O-ring gets replaced from the O-ring kit, not reused.
    3. Grease lightly with the correct silicone O-ring grease — a thin, shiny film, not a glob. The grease helps it seat and slide; it is not the seal itself.
    4. Seat the O-rings fully in their grooves with no twists.

    Watch out for

    • Too much grease attracts grit and can actually unseat an O-ring. Thin and even is the goal.

    Done when

    Every O-ring is clean, undamaged, lightly greased, and seated square in its groove.

    Guide

    parts for this step
  3. 3do

    Install penetrators and blanks

    📦 all 2 in hand

    Every pass-through and every unused hole has to be sealed. Cables go through penetrators; everything else gets a blank.

    Steps

    1. Fit a penetrator for each cable that must pass through the end cap (thrusters, sensors, comms). Follow the maker's method — Blue Robotics WetLink penetrators use a compression seal and need the cable jacket cut square.
    2. Plug every remaining hole with a blank. Do a final count: holes equal penetrators plus blanks, with zero open.
    3. Seat and snug each one — firm, not gorilla-tight. Over-torquing can crack a penetrator or distort the seal.
    4. Grease the penetrator O-rings the same way as the main O-rings.

    Watch out for

    • Note in this step's notes which penetrator carries which cable — you will want that map later.

    Done when

    Every hole is filled (penetrator or blank), each properly seated, with zero open holes.

    Guide

    parts for this step
  4. 4do

    Install the vent / vacuum valve

    📦 all 1 in hand

    The vent / vacuum port is how you will pull the test vacuum, and later how you equalize pressure before opening the housing.

    Steps

    1. Install the vent / vacuum valve (or vacuum test plug) in its port with its O-ring greased and seated.
    2. Confirm it is the test port you will connect the pump to — it should carry a Schrader-style valve or fitting the pump mates to.
    3. Snug, not crushed — same torque discipline as the penetrators.

    Watch out for

    • This is also your pressure-relief and equalization point — never crack open a sealed, evacuated (or later, pressurized) housing without venting it first.

    Done when

    The vent / vacuum valve is installed, sealed, and ready for the pump hose.

    Guide

    parts for this step
  5. 5do

    Assemble the enclosure

    📦 all 6 in hand

    Put the housing together carefully so you do not pinch an O-ring on the way.

    Steps

    1. Slide the end caps and dome into the tube straight and even — no cocking them in at an angle, which rolls or pinches the O-ring.
    2. Seat the O-ring flanges and bring the clamps up evenly — alternate sides a little at a time, like the lug nuts on a wheel.
    3. Listen and feel for the O-ring seating with an even resistance. A sudden easy spot can mean a rolled O-ring.
    4. Double-check nothing is trapped across a sealing face: no cable, label, or debris pinched in the seam.

    Watch out for

    • Take your time here — a clean assembly is half the test.

    Done when

    The enclosure is fully assembled, clamps even, with no pinched or rolled O-rings.

    Guide

    parts for this step
  6. 6do

    Pull a vacuum

    📦 all 2 in hand

    The vacuum test is the gold-standard dry leak check: pull the air out, then watch whether the seal lets it creep back. These figures are Blue Robotics' published guidance.

    Steps

    1. Connect the hand vacuum pump to the vent / vacuum plug's valve (it fits a 1/4 inch hose).
    2. Pump the housing down to about `15 inHg` of vacuum. That is roughly 152 pumps for an empty 4 inch enclosure (about 85 for a 3 inch, 38 for a 2 inch) — fewer once it is packed with electronics.
    3. Close / isolate the valve so the pump is no longer holding the vacuum — the housing must hold it on its own.
    4. Note the gauge reading and the time. That is your baseline for the hold test.

    Watch out for

    • You should hear the housing tighten up as the caps pull in slightly — that is normal and a good sign.

    Done when

    The housing is pulled down to about 15 inHg and isolated, with a baseline reading noted.

    Guide

    parts for this step
  7. 7check

    Vacuum holds

    This is the actual pass/fail. A sealed housing holds the vacuum; a leaky one lets the gauge climb back toward zero.

    What good looks like

    1. Let it sit and watch the gauge for 10 to 15 minutes (longer, or overnight, for real confidence).
    2. A good seal: the vacuum drops by no more than 0.5 inHg over that window (a tiny initial settle as temperature equalizes is normal).
    3. A leak: the gauge steadily climbs back toward atmospheric — the faster it climbs, the bigger the leak.

    If it leaks

    1. Re-check the easy stuff first: the vent valve and every penetrator and blank seated and greased.
    2. Listen at the seams and penetrators for a faint hiss while it is under vacuum.
    3. Re-seat suspect O-rings (clean, inspect, light grease) and pull the vacuum again.

    Do not move on until it holds. A housing that will not hold a bench vacuum will absolutely flood underwater.

    Done when

    The vacuum holds within 0.5 inHg over 10 to 15 minutes.

    Guide

  8. 8do

    Shallow dunk test

    📦 all 1 in hand

    A vacuum hold proves the seal in air; a shallow dunk proves it against actual water before you trust it any deeper.

    Steps

    1. Drop the leak sensors (or a few folded paper towels) inside before you close it, positioned low where water would pool.
    2. Submerge the sealed housing in a tub, sink, or the shallow end of a pool for a short soak — minutes, not hours.
    3. Keep it shallow. This is a seal confirmation, not the deep pressure test — that is its own milestone.
    4. Watch for bubbles streaming from any seam or penetrator. A steady bubble trail is a leak.

    Done when

    The sealed housing has had a short shallow soak with no bubble trails.

    parts for this step
  9. 9check

    Bone dry inside → seal passed

    The payoff check. Vent first, then open and inspect.

    Steps

    1. Equalize before opening. Crack the vent / vacuum valve to let pressure equalize — never pry open a housing that is still under vacuum or pressure.
    2. Open and inspect. The inside is bone dry — no droplets, no damp paper towels, leak sensors reading dry.
    3. Any moisture at all is a fail. Even a few drops means a slow leak; find it and retest.

    Done when

    The housing holds vacuum and comes out of the dunk bone dry. That is the watertight seal test passed — the gate before any electronics go into the hull.