Water resistance (Wasserdichtigkeit)
A watch's rated ability to withstand water pressure, expressed in meters or bar. Pressure ratings are laboratory values and do not directly correspond to depths a wearer can safely use the watch at; the gap matters in dealer-to-customer communication.
Water resistance (German Wasserdichtigkeit) is a watch's rated ability to withstand water pressure, expressed in meters or bar (1 bar ≈ 10 meters of static water pressure). It is laboratory-measured under static pressure, which is one of the most-misunderstood specifications in retail watch selling.
What the ratings really mean
Industry conventions, not strict standards:
- 30m / 3 bar. Splash-resistant. Safe in rain, hand-washing. Not safe for swimming.
- 50m / 5 bar. Safe for light swimming in still water. Not for diving or showering.
- 100m / 10 bar. Safe for swimming, snorkelling, and recreational water sports.
- 200m / 20 bar. Suitable for scuba diving to recreational depths.
- 300m / 30 bar and above. Professional dive depths. Most dedicated diver watches (Submariner, Sea-Dweller, Seamaster Diver, Tudor Pelagos) live here.
The gap between rated meters and actual safe use exists because real-world conditions add dynamic pressure: jumping into water, swimming strokes, water-jet streams. A 30m watch worn in the shower can fail because the shower stream exceeds 3 bar locally.
Why dealers care
Three reasons:
- Customer disputes. A customer who showered with a 30m watch and got water inside will return the watch claiming it was defective. The dealer needs to explain the rating versus use convention clearly before the sale.
- Service implications. Water resistance depends on gaskets, crown integrity, and case seal integrity. Each manufacturer service replaces gaskets and pressure-tests the watch. A watch that has not been serviced in 5+ years should be assumed to have degraded water resistance regardless of its stated rating.
- Cosmetic ratings. Some non-sport watches are sold with low ratings (30m or "splash-resistant") for marketing reasons even though the case construction may handle more. The label is the legal commitment.
Pressure testing
Every manufacturer service includes a pressure test against the watch's rated specification. Independent watchmakers should do the same after any work that opens the case (gasket replacement, battery change, movement service).
A failed pressure test on a previously water-resistant watch usually means one of:
- Worn or compressed gaskets.
- Damaged screw-down crown threads.
- Crystal seal failure (usually after impact).
- Case-back gasket compromised by improper closing.
Disclosure in sales
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 the rated depth could not be confirmed (e.g., very old vintage where the manufacturer no longer pressure-tests to original spec).
- "Not pressure-tested. Treat as water-resistant only to splash level." Honest position for un-serviced inventory.
Avoid stating original-rated water resistance for pre-owned watches without recent testing — this is the most common dispute source in watch returns.
Related: manufaktur-service, master-chronometer, cosc, service-history.