Wednesday, November 19, 2008

Installing a pee valve

If you've been diving in a dry suit for any length of time, you've more than likely had a few dives where you couldn't get out of the water fast enough to go pee.

A little background

This phenomenon is caused by something called Immersion Diuresis. In short, the cold water causes blood vessels in your extremities to constrict, resulting in an increased volume of blood in your core. Your kidneys then go to work producing urine to reduce the volume. Read the details on the DAN web site.

The urge to pee may just be a minor annoyance. But if you start limiting your water intake before diving to avoid the urge, you are increasing the likelihood of DCS.

We dive in 45ºF water most of the year, and staying warm enough to prevent Immersion Diuresis can be a challenge. After I recently lost about 10 pounds building an addition on my house, I found I was getting noticeably colder while diving. The urge to pee quickly set in after I started to get chilled, resulting in many unpleasant safety stops. Because I like to be safe and stay hydrated, I decided to install a pee valve in my High Tide dry suit.

What pee valve should I get?

Pee valves come in two basic flavors: balanced and unbalanced. Balanced valves include a small check valve to allow air from your suit to automatically equalize the pressure in the plumbing. The valve is implemented as a reed valve teed into the drain hose or as a ball valve in the body of the pee valve itself. This generally results in reduced effort to open the valve and avoids any unpleasant squeeze, but also creates an opportunity for leaking.

Previously, I installed a Halcyon balanced pee valve in my Apollo suit, but I actually never used it during a dive. I couldn't bring myself to test it out, and I upgraded to the High Tide shortly after that anyhow. When I finally overcame my reluctance to put a hole in my new suit, I bought an OMS balanced valve because it had a slightly smaller form factor.

It's my opinion that the Halcyon and OMS valves are functionally equivalent, cost about the same, and are equally simple to install. The Halcyon does come with a screw top that you can close in the event of a leak, but it's just one more thing to fiddle with. The OMS valve has the advantage of not being glued to the suit, so it's possible to remove it to clean or move to another suit.

After about 50 dives, my OMS check valve started leaking, even though I cleaned it religiously. After a few attempts at fixing it, I decided to just plug it with a bolt and some teflon tape. After another 100 dives or so, it's still working great that way. Therefore, I'd recommend going with an unbalanced valve and only add a check valve if you have problems.

Installing the valve in your suit

Installing the valve is not hard, but mistakes can be costly if you have to pay someone else fix them. That said, about the only way to mess this up is to put the hole in the wrong place or use the wrong glue.

Here's what you'll need:
  • Your pee valve
  • A hole punch of the correct size (5/8" for the OMS valve) -- you can also burn or cut the hole, but a punch is cleaner
  • Neoprene glue (I used McNett's Black Seal Cement)
  • Duct tape
  • 60 grit sandpaper (or something close)
  • An Xacto knife
  • A clamp and wood blocks (optional)
  • Quick-disconnect fittings (optional)

Where to put the hole?

Everyone recommends putting the hole on the inner thigh. If you install the valve too high, you won't have room for the plumbing. If you install it facing your other leg, it might get dislodged when you walk or swim. Therefore, the best location is just above your knee, aimed slightly inward toward your other leg.

Put your suit on and mark the hole location. Then take the suit off, place a wood block inside behind the hole location, and punch the hole.

I've read of people forgetting the wood block and ending up with two holes in their suit. If you think you're capable of making this mistake, you might want to think about having someone else install your pee valve. =)

Building a glue gasket

My suit has an armor coating on the outside. Even if yours doesn't, it's a good idea to build up a good surface to glue the pee valve rubber gaskets to.

Stick a couple of pieces of duct tape together to form your glue mask. Then cut out a circle that's the same size as your pee valve gaskets and center this over the hole you made in your suit.

Now apply at least three coats of glue, waiting 30 minutes between coats. I used four coats on the outside because the texture of the armor is quite deep. Repeat on the inside, and allow the glue to dry overnight.

Remove the duct tape after the glue is dry. If the glue sticks to the tape, use the Xacto knife to cut it free.

You should now have a nice, clean glue gasket on the inside and outside of your suit.

Glue on the pee valve gaskets

Now you want to bond the gaskets that came with your pee valve to the glue gaskets you made on the suit. I highly recommend doing this one side at a time. If you try to glue up the inside and outside at the same time, you are likely going to end up with glue everywhere.

Rough up the suit-side of the valve gasket with the sandpaper. Then put a final assembly coat of glue on the valve gasket and your outside glue gasket.

Wait about five minutes for the glue to become tacky. Press the rubber gasket onto the suit firmly, and place wood blocks outside the suit, inside the suit and under the suit. Clamp the wood blocks together.

While you could just screw down the two halves of the pee valve at this point, using clamps and wood blocks distributes the pressure and prevents the neoprene from getting crushed. It also keeps the valve from getting glued in place, since you'll want to be able to remove it later.

Let this sit for 5-10 minutes and repeat for the inside rubber gasket.

Once the two rubber valve gaskets are bonded to your suit, you can screw the two halves of the pee valve together. Just be careful not to overtighten it and crush the neoprene.

For information about adding quick-disconnect fittings and selecting the condom catheters, read on.

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