The Ins & Outs of P-Valves

Every diver learns the importance of proper pre-dive hydration. Although some dive agencies are now downplaying the role that dehydration plays in decompression sickness the evidence still points to our body’s need for liquid as one important safeguard against DCS. In simple terms, proper hydration aids our circulatory system by helping ensure dissolved nitrogen (and helium, when diving trimix) comes out of solution as we ascend. Whether you dive within recreational no-decompression limits or engage in planned decompression dives, getting those bubbles out of your blood by practicing slow ascents and making deco or safety stops is critical.

On a hot day, hydrating is as simple as drinking a steady supply of water in small, frequent doses. When it’s cold outside, substituting warm water or tea can help us consume adequate pre-dive liquids while also helping keep you warm. It’s important to start hydrating early—by the time your body becomes dehydrated, it takes many hours of steady liquid intake before your blood gets the message. As a test of proper hydration, your urine should be clear or very pale yellow. If it’s not, you should be drinking more water.

All this liquid has to go somewhere. On a relatively short dive in warm water, most of us can get by with a pre-dive visit to the restroom or dive boat head. On longer dives, and on just about any dive in cold water, the urge to relieve bladder pressure can prompt a diver to head for the surface well before gas supply or decompression obligation signals that it’s time to go. When diving in an overhead environment such as a cave or wreck, or when mandatory deco restricts the diver’s ability to head for the surface at will, bladder pressure can build to the point of discomfort.

Diving in warm water, exposure protection is often limited to a dive skin or neoprene wetsuit. You’ve probably heard the saying that there are two kinds of divers—those who pee in their wetsuits, and those who fib about it. Drysuit divers don’t have that luxury, and too many divers deprive themselves of proper hydration in a misguided effort to stave off the call of nature as long as possible.

It doesn’t have to be this way. Early technical and commercial divers—both of whom spend extended periods in their drysuits—had few options other than holding it, or wearing bulky and uncomfortable adult diapers beneath their insulating undergarment. Today the technology exists to allow drysuit divers to relieve themselves as needed throughout the dive with the installation of a P-valve. If you’ve never used one, this article will give you a sneak preview as well as a few “technical details” that can help you avoid some of the drawbacks sometimes associated with P-valves.

What is P-Valve?

The P-valve consists of a small one-way valve that is installed in your drysuit, usually near the top of either the left or right leg just below crotch level. Most models have a small, low-profile knob the diver can turn to open or close the valve although many divers leave the valve in the open position throughout the dive.

On the inside, a flexible tube runs from the inside of the valve to the correct anatomical location. Although women’s models are available, achieving a comfortable and leak-proof attachment can be problematic. Male divers have it easy by comparison, as external condom catheters with medical-grade removable adhesive generally permit a good seal with little discomfort. As part of dressing in, the diver routes the flexible hose through the lower zip of his undergarment, then makes the connection to the external catheter. As the drysuit is pulled up and readied for closure, it helps to perform a quick check of the hose routing to make sure there are no kinks, and that the hose does not press uncomfortably on the skin.

Once everything is in place, the P-valve is ready for action. It can be disconcerting to intentionally urinate in your drysuit for the first time, but with a little practice it quickly becomes automatic. There is a slight feeling of back-pressure due to the extra plumbing, so a “slow and steady” stream typically works better than saving it up for a big push. Many divers report a dramatic difference in their comfort level before and after adding a drysuit P-valve, particularly in cold water where the need to urinate comes on faster and with greater urgency. Knowing that you can answer nature’s call, it’s a lot easier to make sure you consume enough liquids before the dive. On hot days, it is particularly refreshing to be able to suck down a big drink of water right before diving as your “unplumbed” buddies look on thirstily!

Retrofit a P-Valve to your Drysuit

At Monterey Bay Diving, we sell and install all brands of P-valves and we can install them in any brand of drysuit. Turn-around time is typically two weeks or less. The valve is glued in place and given the same leak test as all our drysuit repairs and modifications. You can source condom catheters at any local retailer that sells adult medical supplies, or purchase online at a discount.

Stop depriving yourself of proper pre-dive hydration because you don’t want to “go” during your dive! Visit us online or call us today to see how we can help you dive more safely and comfortably with a professionally-installed drysuit P-valve from Monterey Bay Diving.

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