Why Follow The Quarter Turn Back Valve Practice

Jerry Otte   Dec 07, 2021

Written by: Jerry Otte, PADI Master Instructor, AAI Service Technician

This year I notice that a greater number of our tank valves at Aquatic Adventures were failing than in previous years. To ensure that our valves work reliably for our divers, we make a practice of serving our valves every five years when the cylinders come up for their hydrostatic test. Rarely, will a valve fail even with heavy use if it serviced every five years. This is why I was both surprised and concerned when valves I had serviced in February were failing by October.

Valve assembly for XS Scuba valve.Let’s examine what happens during valve servicing. During the overhaul of a cylinder valve, the valve is disassembled, and all reusable parts are cleaned. Next, the valve burst disk, O-rings, Teflon washers, and any other parts that show significant wear are replaced with new parts from the valve manufacturer. After reassembly, valves are tested for leaks to ensure they are in working order. The result is a smoothly operating valve that looks and works as though it were new.

Because we follow these valve service procedures carefully, I found it odd that so many valves were failing within months of an overhauled. I raised the issue with two members of our staff one afternoon when they returned a tank with a leaking valve. I had serviced that valve just 6 months earlier, and the valve showed signs of significant wear. During our discussion, one of the instructors indicated that he no longer reviewed turning the valve slightly back after fully opening it. He cited an article from DAN published at the beginning of the year as his reason.

For your reference, the DAN article from Alert Diver - Q1 2021 the instructor cited can be found at this URL: https://dan.org/alert-diver/article/old-habits-die-hard/. While there is plenty of accurate information on valves in the article, the author jumps to a remarkable and completely unsupported conclusion. The author asserts that because divers have been told to turn their cylinder valve a quarter turn off full open, divers are descending with their tank valves only partially open. There is also an unsupported suggestion that turning a valve a quarter turn off full open confuses divers as to which direction is open and which is shut, resulting in the diver turning their valve closed.

As the only real documented evidence of the quarter turn advice leading to a dive accident, the DAN author cites an Alert Diver article written by Christina Hepburn in 2017. You can read that article at this URL: https://dan.org/alert-diver/article/an-emergency-ascent-just-in-time/. When you do, you will find that the incident in question resulted from the failure to open the cylinder valve entirely. There is no mention at all that the diver was told to turn back a quarter turn or that those instructions directly resulted in the diver’s valve being left partially open. There is also no indication that a divemaster on the boat was confused and didn’t open the diver’s valve properly.

For a moment, let’s look at why divers have been told to turn the valve back a quarter turn off fully open. As the DAN author correctly states, forcing a valve fully open or fully shut can damage the valve. She incorrectly suggests that newer valves are somehow impervious to this kind of abuse. For the record, they are not.

Valve damaged by forced turningThe valves in our rental fleet that failed prematurely all exhibited evidence of forced opening or closing. You can examine your own valves for this type of wear by removing the valve handle and examining the valve stem. Forcible turning wears out the Teflon washer located on the valve stem and within the bonnet nut. As the washer shreds from this abuse, it leaves a white residue that looks like spider webs in the valve assembly. Once this residue appears, it is just a matter of time before the valve begins turning hard. Eventually it will leak.

Now I do not know what experience the DAN author has with training students or leading dives. I can only talk about my experience. During the last calendar year, I have led more than 200 dives with students and certified divers. I have always made a practice of asking divers to check that their valves are fully open with a quarter turn back, explaining that it is imperative that the valve is fully open for proper operation and that a quarter turn back will prevent them from forcibly opening the valve to the point where the valve gets damaged. I emphasize that a quarter turn back will not impact the functionality or performance of the valve.

On three occasions this year I caught divers during our buddy checks with a valve that was only partially open. In one case, I caught the same diver on back-to-back dives with his valve barely open. Each of these divers indicated that they did not realize that they had not opened their valves all the way. None of them indicated that they were confused about which way to turn the valve. All of them indicated that they had never opened the valve all the way in the first place.

Obviously, we could debate whether the quarter turn back advice has been responsible for diver accidents. In my opinion, these cases are at best extremely rare. No doubt there is a confused diver or divemaster somewhere that may have had or caused an accident or near accident because they didn’t open a valve properly. However, there can be no debate about whether forcing a valve open will damage the valve. The timing of our instructors omitting the normal discussion of proper valve care and the rapid increase in damaged valves at our store suggests this is a real problem.

My advice to instructors and divemasters is to clearly explain to divers how to properly care for their equipment, prevent damage, and ensure reliability. Then back up that advice by insisting on a good buddy check before every dive to catch any errors made by someone who is confused.