Water Resistant or Divers?
Not all sports watches are diving watches, but all diving watches are sports watches! The below sections are for information on the differences, but be rest assured at Autodivewatch we only sell watches that are suitable for all activities, with a minimum water resistance of 200m!
A watch is not water resistant unless stated on the dial or case back. Watches which are not marked water-resistant should always be removed whilst washing etc.
Water resistance is measured in bars (a bar is a unit of pressure, 1 bar being equivalent to 1 atmosphere), and watches are tested at these pressures in a static laboratory test for a short period of time. Exceptional pressure, as when diving, or prolonged and active use in water may exceed those limits. If the watch is to be used for diving or impact water sports it will need to be able to tolerate that extra pounding. Thus in all practicality the limits stated on the watch should always exceed those of its actual use.
Translation of water resistance varies and the best guide is the supplier or maker of the watch as it will almost certainly be part of the guarantee, and should now meet with the international standard of ISO 22810:2010 when stating water resistance. Manufacturers often measure water resistance to a number of feet, meters or atmospheres (ATM). Normally, terms of depth imply that a watch will remain resistant at this (Atmospheric pressure) depth in still conditions. As a general rule, the minimum could be described as follows:
3 ATM or 3 BAR (30 m or 100 ft)
Everyday use, it can withstand a gentle splash such as rain but is not suitable for swimming.
5 ATM or 5 BAR (50 m or 165 ft)
Everyday use and swimming, splash in pool but not suitable for pool side diving or water sports.
10 ATM or 10 BAR (100 m or 330 ft)
Everyday use, poolside diving and snorkelling. Not suitable for high board diving, high impact or water sports.
15 ATM or 15 BAR (150 m or 500 ft)
Everyday use, poolside diving and snorkelling, most water sports.
20 ATM or 20 BAR (200 m or 660 ft)
Minimum required for high board diving, high impact water sports or sub aqua diving. The only watches, which are designed to withstand continued use in these conditions, are professional divers watches. Only watches marked "DIVER'S" on the dial should really be used for diving as these fully comply with the international standards for diver's watches.
It is wise to remember that when mountain climbing, parachuting, sky diving, hang gliding, or skiing, you may also require a watch that is ATM damage-protected, as pressures change both above and below sea level. Always ensure that any screw down crowns or pushers are properly fastened tight. Failure to do this will compromise the water resistance of your watch and invalidate any warranty, if water enters because they were not screwed down!
ISO 6425 divers' watches standard
The standards and features for diving watches are regulated by the ISO 6425 - Divers' watches international standard. This standard was introduced in 1996. ISO 6425 defines such watches as: A watch designed to withstand diving in water at depths of at least 100 m and possessing a system to control the time. Diving watches are tested in static or still water under 125% of the rated (water) pressure, thus a watch with a 200-metre rating will be water resistant if it is stationary and under 250 metres of static water. ISO 6425 testing of the water resistance or water-tightness and resistance at a water overpressure as it is officially defined is fundamentally different from non-dive watches, because every single watch has to be tested. Testing diving watches for ISO 6425 compliance is voluntary and involves costs, so not every manufacturer present their watches for certification according to this standard.
ISO 6425 testing of a diver's watch consists of:
Reliability under water. The watches under test shall be immersed in water to a depth of 30±2 cm for 50 hours at 18 to 25 °C and all the mechanisms shall still function correctly. The condensation test shall be carried out before and after this test to ensure that the result is related to the above test.
Condensation test. The watch shall be placed on a heated plate at a temperature between 40 and 45 °C until the watch has reached the temperature of the heated plate (in practice, a heating time of 10 minutes to 20 minutes, depending on the type of watch, will be sufficient). A drop of water, at a temperature of 18 to 25 °C shall be placed on the glass of the watch. After about 1 minute, the glass shall be wiped with a dry rag. Any watch which has condensation on the interior surface of the glass shall be eliminated.
Resistance of crowns and other setting devices to an external force. The watches under test shall be subjected to an overpressure in water of 125% of the rated pressure for 10 minutes and to an external force of 5 N perpendicular to the crown and pusher buttons (if any). The condensation test shall be carried out before and after this test to ensure that the result is related to the above test.
Water-tightness and resistance at a water overpressure. The watches under test shall be immersed in water contained in a suitable vessel. Then an overpressure of 125% of the rated pressure shall be applied within 1 minute and maintained for 2 hours. Subsequently the overpressure shall be reduced to 0.3 bar within 1 minute and maintained at this pressure for 1 hour. The watches shall then be removed from the water and dried with a rag. No evidence of water intrusion or condensation is allowed.
Resistance to thermal shock. Immersion of the watch in 30±2 cm of water at the following temperatures for 10 minutes each, 40 °C, 5 °C and 40 °C again. The time of transition from one immersion to the other shall not exceed 1 minute. No evidence of water intrusion or condensation is allowed.
An optional test originating from the ISO 2281 tests (but not required for obtaining ISO 6425 approval) is exposing the watch to an overpressure of 200 kPa. The watch shall show no air-flow exceeding 50 μg/min.
Except the thermal shock resistance test all further ISO 6425 testing should be conducted at 18 to 25 °C temperature. Regarding pressure ISO 6425 defines: 1 bar = 105 Pa = 105 N/m2. The required 125% test pressure provides a safety margin against dynamic pressure increase events, water density variations (seawater is 2% to 5% denser than freshwater) and degradation of the seals.
Movement induced dynamic pressure increase is sometimes the subject of urban myths and marketing arguments for diver's watches with high water resistance ratings. When a diver makes a fast swimming movement of 10 m/s (32.8 ft/s) (the best competitive swimmers and finswimmers do not move their hands nor swim that fast) physics dictates that the diver generates a dynamic pressure of 50 kPa or the equivalent of 5 metres of additional water depth.
Besides water resistance standards to a minimum of 100 metres (330 ft) depth rating ISO 6425 also provides minimum requirements for mechanical diver's watches (quartz and digital watches have slightly differing readability requirements) such as:
The presence of a time-preselecting device, for example a unidirectional rotating bezel or a digital display. Such a device shall be protected against inadvertent rotation or wrong manipulation. If it is a rotating bezel, it shall have a minute scale going up to 60 min. The markings indicating every 5 min shall be clearly indicated. The markings on the dial, if existing, shall be coordinated with those of the preselecting device and shall be clearly visible. If the preselecting device is a digital display, it shall be clearly visible.
The following items of the watch shall be legible at a distance of 25 cm (9.8 in) in the dark:
time (the minute hand shall be clearly distinguishable from the hour hand);
set time of the time-preselecting device;
indication that the watch is running (This is usually indicated by a running second hand with a luminous tip or tail.);
in the case of battery-powered watches, a battery end-of-life indication.
The presence of an indication that the watch is running in total darkness. This is usually indicated by a running second hand with a luminous tip or tail.
Magnetic resistance. This is tested by 3 expositions to a direct current magnetic field of 4 800 A/m. The watch must keep its accuracy to ±30 seconds/day as measured before the test despite the magnetic field.
Shock resistance. This is tested by two shocks (one on the 9 o'clock side, and one to the crystal and perpendicular to the face). The shock is usually delivered by a hard plastic hammer mounted as a pendulum, so as to deliver a measured amount of energy, specifically, a 3 kg hammer with an impact velocity of 4.43 m/s. The change in rate allowed is ±60 seconds/day.
Resistance to salty water. The watches under test shall be put in a 30 g/l NaCl (sodium chloride) solution and kept there for 24 hours at 18 to 25 °C. This test water solution has salinity comparable to normal seawater. After this test, the case and accessories shall be examined for any possible changes. Moving parts, particularly the rotating bezel, shall be checked for correct functioning.
Resistance of attachments to an external force (strap/band solidity). This is tested by applying a force of 200 N (45 lbf) to each springbar (or attaching point) in opposite directions with no damage to the watch of attachment point. The bracelet of the watch being tested shall be closed.
Marking. Watches conforming to ISO 6425 are marked with the word DIVER’S WATCH xxx M or DIVER'S xxx M to distinguish diving watches from look a like watches that are not suitable for actual scuba diving. The letters xxx are replaced by the diving depth, in metres, guaranteed by the manufacturer.
(Sourced from Wikipedia )