The “P-Valve,” Avoiding a Wet Drysuit

By Steve Lewis

PValveOK, hands-up all of you who have taken a pass on that extra glass of water because you’re about to zip yourself into a drysuit and go diving? Better yet, how many of you have been wrapped in the comfort of your drysuit hanging on a safety-stop at the end of a nice long dive WISHING you had taken a pass on that extra glass of water?

Well, the solution to that particular challenge is to dive with a “P-valve,” and for those of you unfamiliar with the concept of punching a hole in a perfectly good drysuit to retrofit this little convenience, let’s say right up front, I cannot think of a better way to spend a few pennies. (Forgive the pun). Let’s explore some of the reasons why. There is a tenuous connection linking hydration and DCS. While most of us have “grown-up” listening to advice from trusted sources such as DAN (Diver’s Alert Network), Duke University Medical Center, and various hyperbaric and technical diving gurus telling us that being well-hydrated helps to off-set some of the risk of decompression stress, the scientific papers to back this advice up with solid data are thin on the ground. However, many of what passes for leading authorities in the technical diving community fly in the face of science and swear that good hydration is key to a successful outcome on any and all dives.

“Dive Hydrated” is the common mantra and most of us follow that guideline without question. And regardless of the position of the medical and scientific establishment with regards DCS and hydration, there are volumes of papers and reports in sports medical journals pointing to the importance of good hydration and the peak performance of mind and muscles in athletes. You may or may not feel this is entirely relevant to you and your diving, but I believe it is to mine. There have been occasions when I have felt sluggish and a little dimmer than usual and the physical problem has been dehydration. Therefore, my daily average intake of about three litres of water is unchanged by the diving calendar; and ample water intake pre, post and sometimes during a dive has become the norm. But this behavior does bring up the potentially embarrassing issue of bathroom breaks while zipped into one’s “thermal protection.” Essentially: how and where?

Let’s discuss the “How” first. There are of course, adult-sized diapers for both men and women, and while these may be a viable solution for some, diapers are not the most green of products and are certainly not the most reliable, hygienic or comfortable. It’s unclear who first decided that a better solution to the question HOW was to plumb a piece of hose to a simple-to-open valve on the diver’s leg, which when closed kept water out, but when opened allowed liquids to be dumped “off-board.” The connection between the outside of the suit and the male diver was achieved with a little medical device known as a condom catheter (more on these later). My first encounter with a so-called “P-Valve” occurred while cave-diving in North Florida. Fixing a newly purchased model to what had been a perfectly dry drysuit, required some will-power, the empty brass cartridge from a .45 caliber pistol, a hammer, and a strategically placed piece of wood on the left thigh of the suit. Once the hole was made – clean and the perfect size – liberal amounts of sealant and exact positioning of bolts, nuts and washers, resulted in a watertight seal. As an aside, I have since owned more than 10 drysuits, all of which have been fitted – either by the suit manufacturer or as a post-sale upgrade – with a P-valve of some sort or another, and quite remarkably, all have functioned well. All that remained during my very first experiences with a P-Valve was the connection between it and me.

Enter the external male catheter. The ubiquitous Google search will turn up countless amusing and sometimes alarming stories focused on the… issues… divers around the world have suffered through coming to terms with the fitting, successful use of, removal and disposal of condom catheters. I am going to resist the urge to add my experiences over and above the following advice. While condom catheters are essentially a small latex or silicone tube with one end designed to connect it and its wearer to some sort of plumbing… including a drysuit’s P-valve there are subtle differences between Brand X and Brand Y. External male catheters are available in several different models, different materials, and yes, different sizes. They can be purchased in bulk online from several different medical supply houses and many dive centers carry a small stock for folks who only need to buy in smaller quantities.

Your mileage may vary, but the most popular and best-selling according to a spokesperson at one of the largest online suppliers, Lighthouse for the Blind, based in St. Louis, Missouri, is self-adhering and non-latex. This model has a wide-band of “glue” on the inside to help keep it in place, which is certainly an asset when diving, but that takes a brave soul to remove from its place of work from time to time. One more thing: “What you divers have to consider,” said the nice spokeswoman at Lighthouse. “Is that these items were designed to hold fast to someone either in a wheelchair or invalided in bed, and not swimming around in the ocean.” She insisted that getting the correct size is important to “staying connected” and I agree with her! We can leave this topic with a tip of the hat to the women responsible for the design and manufacture of the “She-P:” the corresponding piece of kit to an external male catheter for female divers.

PValve2While far from perfect – according to female dive buddies – this rather mystifying, and reasonably newly-launched contraption has revolutionized a day on the boat for hundreds of women divers… tech and sport. It allows them, like their male counterparts, to connect themselves to an outboard dump and conduct dives well-hydrated (ask DUI about She-P). Welcome to the club! It may also come as no surprise to a savvy observer with a grasp of basic physics that a simple piece of tubing connected to a “flow-through” bolt or twist-to-open valve on the outside of a drysuit would be an unbalanced system. That’s to say that the pressure in the suit, the ambient pressure outside the suit, and the pressure inside the valve’s plumbing are not the same. For the best results, and fewest unpleasant surprises, the plumbing in an unbalanced system is best primed before the diver subjects him or herself – and their equipment – to increased ambient pressure. If this step is neglected, the sudden “equalization” of pressure between the closed bolt, conjoining hose and apparatus on the inside of the suit to the water pressure outside, can be a shocker… to say the least. An option available very soon after the introduction of the “store-bought” unbalanced P-Valve was a balanced system. This type of dump is fitted with an additional little side-branch of hosing designed to equalize the whole of the valve with the pressure inside the diver’s suit, which in turn is supposed to do away with the need for pre-priming the system. Some divers swear by balanced valves and others swear at them because – they maintain – a balanced system is way more prone to leaks… and those leaks are often NOT the result of water that started life outside the suit getting inside the suit.

I think we can wrap this up with one final item: cleanliness. There are several suggestions for maintaining a clean and hygienic off-board dump. I know several rebreather divers who flush their P-valves with the same solution that they use to disinfect their counter lungs. Some other divers flush their P-valve system with a mix of white vinegar and rubbing alcohol and then rinse with water. Some use a dilute bleach solution. I use a 10 percent solution of Dettol™, a liquid antiseptic and disinfectant available over-the-counter in most drug stores. It smells of pine oil and the active ingredient is chloroxylenol – a pretty powerful germ killer. I first encountered the use of dilute Dettol as a topical disinfectant for open wounds and figured that if it’s OK for the Royal Hampstead Teaching Hospital, it’s probably OK to rinse out my P-Valve and the inside of my drysuit with it. Once again, your mileage may vary, but Dettol followed by a thorough rinse with fresh water has kept me safe from any infections for many, many dives.

Well, there really isn’t much to add except to restate that even though the jury MAY still be considering the verdict on the relationship between thorough hydration and DCS, many of us choose to drink lots of water when we dive, and feel better for being able to get rid of some of it during our dive! Oh, that brings us to the unanswered question of WHERE. Well, not to put too fine a point on things: wherever. Dive safe.

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One Response to The “P-Valve,” Avoiding a Wet Drysuit

  1. Joe L. says:

    I would like to mention that there are many products for easily removing the glue used in the catheters. Most medical supply places carry an adhesive remover, But don’t always tell you this when you buy the catheters.(I asked after the first time I used one…) A web search for “medical device adhesive remover” also works well.

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