DH free Flow

[tall78]

I'm new to this form of diving. My question is that my DH free flows on the surface. Is this normal?? What corrections should I make ,if any? I already lowered my reg to the center of my shoulder blades and this really helps the breathing process, but it seems to make the free flow worse. I purchased Bryan's mouthpiece plugs for the curved mouthpiece, which doesn't quite fit snug enough. But maybe I need a new mouthpiece? Please let me know what I can do to solve this problem, Thanks

[Drado]

If you're on the surface with the mouthpiece above water and the diaphragm submerged (such as when floating on your back), the reg will definitely free flow. Try to get the mouthpiece below the level of the reg or use the plug than you have. It should fit. Are you using a silicone mouthpiece or an original rubber one?

[Herman]

Freeflowing at the surface....or in any position that puts the cans lower than the mouthpiece, like swimming on your back....is normal for a DH reg and something a DH diver has to learn to deal with. When you are at the surface and allow the cans to go under water, the pressure of the water tries to fill the cans, it can't because of the regs diaphragm but it can and will apply pressure to the diaphragm causing it to move inward, starting the flow. The design of the reg is such that once flow of a sufficient level has started, the venturi feature of the reg will assist the flow, pulling the diaphragm in even farther increasing the freeflow. If the mouthpiece is lower that the cans, the water pressure is greater there than at the diaphragm and keeps the diaphragm from moving in. The better the reg is tuned for optimal performance, the more prone to freeflow it will be. It is possible to set up a DH to not freeflow at the surface but you will not like how it performs underwater. This is also a problem with single hose regs if you ease one into the water mouthpiece up. Divers are taught to fill the second stage on single hose regs to prevent the freeflow, with equal water pressure on both sides of the diaphragm, the problem does not exist. Clearing a fully flooded single hose second is easy, it is not as simple with a DH reg.
Using a mouthpiece plug will help or simply holding the mouthpiece under water will stop it from free flowing unless you lean back, putting the cans deeper. Try not to lean back at the surface and when in shallow water, avoid getting over chest deep if possible. As much as I hate snorkels, this is one time they can come in handy. For long surface swims, go face down with the snorkel to keep the cans out of the water. Unfortunately, it is a fact of DH life we have to learn to deal with if we want to dive DH regs, a small price to pay IMO.

[antique diver]

When I am upright at the surface I can usually slip my right arm up through the hose assembly, then with my arm back down the mouthpiece is easily held lower than the reg body... preventing free flow, but keeping both hands free. If you are large this may not work for you. Be sure your hoses are well secured at all ends to prevent pulling a hose off the horns or mp. Best not done with hoses of questionable condition because one could tear or break if weakened and/or cracked from age. Works best with Silicone hoses.

The VDH mouthpiece plug also works quite well for me when used on USD or VDH curved mp.

Maybe yours is a different type or deformed from age?

[Nemrod]

Double hose free flow on the surface is really of little consequence. It is simply a matter of adapting your diving techniques to the equipment and it's operating requirements.

For long surface swims, I prefer to swim on my back. That way I can navigate, look for boats and use my GPS. I have made shore dives requiring swims of over two miles this way. I turn the air off. There is simply no way around it.

For short swims of several hundred yards from shore then I would use a snorkel and this is how it was done in vintage times of yore.

For surface waits such as waiting for the boat to come get you aka South Florida drift dives, Cozumel drifts etc. some people are using a mouthpiece plug. This way you can lay back on your wing, pop your mask on the forehead and wait for the boat and relax. And, the plug quickly removes so you can get the mouthpiece back where it belongs (in your mouth) quickly as the boat approaches or should you wish to avoid swallowing gallons of seawater on day with rough water.

Of course, if you keep the mouthpiece in your mouth, there is no real issue.

Nem

[tall78]

Thank you very much for all the information. I will be contacting Bryan fur some new silicon mps. Along with other reserve parts. I really appreciate your attention on this matter. I just didn't remember after all these years. I did start with a DH, but quickly changed to Single Hose as production was fased out in the early 70's. I just couldn't remember. Bryan has been very helpful in setting up my Royal Pheonix HPR. My LDS insists on Diver with a BCD. I use Aqua Lungs Axiom. It supports my tank well and doesn't interfere will my DH.

[Chris]

if you want to experience a massive free flow take your tank off under water. I did a spoof video for our dive club on how much easier it is to clear your mask with a double hose than it is with a single hose. When you drop your tank as low as it will go it blows your lungs up like balloons and blows through your sinuses so fast it almost hurts.

http://youtu.be/iuJmiJ0-HDw

[gj1963]

Don't want to sound repetitive.... But it quickly became second nature to me to hold the mouthpiece down with my left hand anytime at the surface to prevent free flow. There are not many (any, except rarely my friend trying one) other DH divers I have spent time with here. I get tons of attention at the local sites and am well known now as the vintage guy. This means I am especially careful and certain of my equipment. A sudden massive freeflow draws eyes very quick.