Tech Tip: Uncoupling DIN Fittings From SCUBA Valves

There is more to disconnecting a DIN fitting from a valve than you might imagine. Do it incorrectly and you will probably lose an O-ring and perhaps even need to have your regulator serviced. The problem is most pronounced in using DIN fittings on fill whips, and more rarely on first stage regulators. The O-ring popping out of the nose of the DIN fitting is an issue on scuba regulators and fill whip hoses and it is caused by failing to completely bleed residual pressure before uncoupling the fitting.

On fill whips, you can be certain all the pressure is released by opening the bleed and waiting a few extra seconds before starting to unscrew the fitting. You need to wait a moment after the hiss stops, because the bleed hole is tiny and gas will continue to escape even after the hissing stops. Compact ring-style bleeds found on fill whips that twist either direction to bleed are popular because you can't lose the bleed screw, but with this design you must make sure the ring is centred on the bleed opening because if you keep twisting you will close it again with out fully bleeding the hose.

Even when divers are using improper technique to unscrew DIN fittings on first stages, they rarely see the problem because usually they are unscrewing the fitting from a nearly empty cylinder with relatively little pressure remaining. But if the cylinder is nearly full and the diver encounters a circumstance where the first stage DIN fitting must be unscrewed then proper technique can very important. Briefly purging the second stage just once is not enough, residual pressure trapped in the high-pressure hose of the SPG will take several seconds to move all the way back through the regulator first stage to the second stage. You must wait a moment between each time you push the purge and you must do it three times in a row to fully release all the pressure from the hoses. Another equally effective two-handed technique is to continue to hold the second stage purge down in one hand while you begin to unscrew the DIN fitting using the other hand.

DIN fitting designs on regulators use a two or three part assembly in which the threaded component with a hand-wheel collar slides onto a hollow centre post and is retained by a 'nose cap' that contains the sealing DIN O-ring on the front and a smaller O-ring on the back. Improperly unscrewing the collared threads by rocking the entire assembly back and forth, or just using brute force to 'break' the seal can eventually can loosen the centre post and/or nose cap causing a leak or seal failure the next time you try to use the fitting. Sometimes you can 'save-a-dive' by using a hex wrench to hand tighten the DIN assembly, but a loose assembly is nearly impossible to permanently correct in the field and usually requires bench service to be able to fully tighten and lock the assembly back in place.

Proper technique to uncouple a DIN fitting requires you be careful to only turn the collar in the DIN fitting — don't grab and turn the entire assembly. If you can't easily turn just the collar to unscrew, i.e. you have to use force on the the entire assembly to 'break' the seal, then the line is not fully depressurised and you need to repeat the bleed.

The Ledges

Reef Dive | Boat access

Depth: 12 m (39 ft) to 16 m (52 ft)

Level: Open Water and beyond.

The Ledges lies off Collendina on the Barwon Coast, east of Ocean Grove and west of Point Lonsdale in Bass Strait. It features an awesome reef structure in 16 metres of water with triple-decker ledges and swim throughs.

This area is not affected by current, but as with all dives close inshore it can be affected by surge.

Bass Strait Warning: Always keep an eye on sea conditions throughout any shore or boat dive in Bass Strait on Victoria's coastline. Please read the warnings on the web page diving-in-bass-strait before diving or snorkelling this site.

Location: Ocean Grove, Victoria 3226

Abalone Dive Site
© Mark Norman, Museum Victoria

Divers have the opportunity to catch Abalone at this dive site. Remember your catch bag, legal abalone tool, current Victorian Recreational Fishing Licence, and abalone measure. Please abide by all current fishing regulations if you intend to catch abalone.

See article-catching-abalone for practical abalone hunting advice from The Scuba Doctor, plus melbourne-abalone-dives for a list of other Abalone dive sites near Melbourne.

Crayfish Dive Site | © Ian Scholey

Divers have the opportunity to catch Southern Rock Lobster (aka Crayfish) at this dive site. Remember your catch bag, current Victorian Recreational Fishing Licence, rock lobster measure, and cray tags. Once you get back to the dive boat, or shore, make sure you clip the tail and tag your Crayfish as per Fisheries requirements. Please abide by all current fishing regulations if you intend to catch crays. See article-catching-crayfish for practical cray hunting advice from The Scuba Doctor, plus melbourne-cray-dives for a list of other crayfish dive sites near Melbourne. For tips on cooking your Crays, please see article-cooking-crayfish.

Wathaurong (Wadda-Warrung) country

Traditional Owners — This dive site is in the traditional Country of the Wathaurong (Wadda-Warrung) people of the Kulin Nation. This truly ancient Country includes the coastline of Port Phillip, from the Werribee River in the north-east, the Bellarine Peninsula, and down to Cape Otway in the south-west. We wish to acknowledge the Wathaurong as Traditional Owners. We pay respect to their Ancestors and their Elders, past, present and emerging. We acknowledge Bunjil the Creator Spirit of this beautiful land, who travels as an eagle, and Waarn, who protects the waterways and travels as a crow, and thank them for continuing to watch over this Country today and beyond.

The Ledges Location Map

Latitude: 38° 17.346′ S (38.2891° S / 38° 17′ 20.76″ S)
Longitude: 144° 34.378′ E (144.572967° E / 144° 34′ 22.68″ E)
Datum: WGS84 | Google Map
Added: 2018-01-12 11:00:00 GMT, Last updated: 2022-04-29 12:55:18 GMT
Source: Allie Beckhurst GPS (verified)
Nearest Neighbour: 18 Metre Reef, 86 m, bearing 313°, NW
Ocean Grove, Barwon Coast.
Depth: 12 to 16 m.

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DISCLAIMER: No claim is made by The Scuba Doctor as to the accuracy of the dive site coordinates listed here. Should anyone decide to use these GPS marks to locate and dive on a site, they do so entirely at their own risk. Always verify against other sources.

The marks come from numerous sources including commercial operators, independent dive clubs, reference works, and active divers. Some are known to be accurate, while others may not be. Some GPS marks may even have come from maps using the AGD66 datum, and thus may need be converted to the WGS84 datum. To distinguish between the possible accuracy of the dive site marks, we've tried to give each mark a source of GPS, Google Earth, or unknown.