Water resistance

Water resistance (German Wasserdichtigkeit) denotes a watch's rated pressure resistance, expressed in metres, bar or ATM. The values come from standardised laboratory tests under static pressure — and are among the most frequently misunderstood specifications in retail watch selling.

The ISO 22810:2010 standard defines the test procedure: the watch is subjected to its rated pressure in a water bath and checked for ingress. A passed test says the watch was statically tight in delivery condition. It says nothing about dynamic load, ageing, gasket hardening or the load of a dive into the pool.

What the ratings really mean

Industry conventions for the steps:

• 3 bar / 30 m. Splash-resistant. Safe in rain, hand-washing. Not safe for swimming.
• 5 bar / 50 m. Light swimming in still water. Not for diving or showering.
• 10 bar / 100 m. Swimming, snorkelling, water sports.
• 20 bar / 200 m. Scuba diving at recreational depth.
• 30 bar / 300 m and above. Professional dive depths. Submariner, Sea-Dweller, Seamaster Diver, Tudor Pelagos.

The gap between rated depth and safely usable depth arises from dynamic pressure in real use: jumping in, swim strokes, directed water jets. A 3-bar watch in the shower can fail because the shower stream reaches 4 to 5 bar locally.

What the resistance depends on

Four components together make a watch pressure-tight:

• Case-back gasket. A sealing ring between case and back, screwed or pressed. Hardens over the years — standard replacement at every service.
• Crown gasket. On screw-down crowns (Rolex Twinlock, Triplock, Omega Naiad Lock) a double or triple gasket. On non-screwed crowns a single ring, more vulnerable.
• Crystal gasket. Between crystal and case rim, often an O-ring. Impact-sensitive — a displaced crystal no longer seals.
• Pusher and valve gaskets. On chronographs and watches with a helium escape valve, additional pressure points.

Every manufacture service replaces these gaskets across the board and pressure-tests the watch afterwards. Anyone who has not serviced a watch in 5+ years can no longer rely on the rated water resistance — irrespective of the printed dial figure.

Why the sale must address this

At our atelier in Munich we see three recurring conflict patterns:

• Complaint after shower. Customer with a 3-bar watch under a hot shower, condensation under the crystal afterwards. The damage is on the customer — the specification was respected. The convention has to be explained before the sale.
• Complaint after pool. Customer with a 5-bar watch in active swimming, sudden water ingress. The 5-bar level is designed for calm swimming, not crawl strokes with dives. Information before the sale is decisive here as well.
• Complaint on vintage. Customer with a 50-year-old Datejust after a beach holiday. The factory 10-bar rating was valid in 1972, not 2026 without a pressure test. A pressure test is mandatory before any water contact on an unserviced vintage watch.

Disclosure at sale

For pre-owned watches the responsible practice is to test water resistance before sale and disclose the result:

• "Pressure-tested to rated depth, [date]." The strongest claim.
• "Pressure-tested to 5 bar, [date]." When rated depth could not be confirmed (typical on vintage).
• "Not pressure-tested. Treat as splash-resistant only." Honest position on unserviced inventory.

Citing original ratings on a pre-owned watch without a current test is the most common dispute source on returns. We avoid it consistently.