Clearing a rebreather

[Adam the Flatulent]

I've never dived a semi closed or fully closed circuit, and don't really have any plans to do so. I'm just intrigued; how do you clear a rebreather? As your exhaust hose goes back into the circuit, wouldn't that push the water back into the circuit?

cheers

[Doppler]

Ah, no. The mouthpiece on a CCR (and an SCR) is not open to the water unless the diver forms an imperfect seal with her/his mouth.

[Cave Diver]

I've never dived a semi closed or fully closed circuit, and don't really have any plans to do so. I'm just intrigued; how do you clear a rebreather? As your exhaust hose goes back into the circuit, wouldn't that push the water back into the circuit?

cheers

The hoses go into the counter lung first, usually with a T-fitting, which allows water to be trapped there and evacuated through an exhaust valve, similar to the one on your BCD.

Flooding and clearing the loop was part of the requirement of my CCR class, but it should be noted that some CCR's are more tolerant to flooding than others.

[wedivebc]

Some rebreathers such as the Meg have a deflector that diverts water into the counterlung where it can be emptied through a dump valve.
Almost every rebreather has a shut off in the mouthpiece to prevent water coming in.

[Dsix36]

Most rebreathers have a means of dumping the water from the breathing loop. Most of the time it is done by some sort of dump valve. Many rebreathers have some form of water trap that prevents the water from traveling through the entire breathing circuit. Some will also have an absorbant pad (like a sponge) to suck up extra water also. There are some units that have no way to remove excess water and if too much is in the loop, the dive must be ended.

As other had stated, the mouthpiece on a rebreather has a lever that opens and closes it. When it is closed, nothing can get into or out of the breathing circuit. The small amount of water that getting into this opening can be purged (must be done with lung volume) out a very small hole in the bottom of it prior to opening the mouthpiece. This way you are not blowing any water into the breathing loop.

[Doppler]

Folks: I think the OP believes that a CCR mouthpiece is like a regulator... not sure he needs to know about redirecting water into the exhalation lungs and purging it... I really think this is a MUCH more basic answer... but hey, that may be a wrong assumption.

[muddiver]

Most rebreather mouth peices have a valve (called an ADV) that the diver turns to go from the rebreather to some sort of alternate breathing source. This same valve should be turned when ever the mouth piece is out of the divers mouth and that will prevent water from entering the return hose to the unit.

It is possible, and has happened, where the diver either forgot to colse the ADV and the rebreather floods. This is really bad because the diver is now very negatively buoyant and just dropping ones weights might not return the diver to neutral or positive buoyancy.

[Cave Diver]

Folks: I think the OP believes that a CCR mouthpiece is like a regulator... not sure he needs to know about redirecting water into the exhalation lungs and purging it... I really think this is a MUCH more basic answer... but hey, that may be a wrong assumption.

You could be right Steve, but I guess it's covered either way now.

[mala]

Most rebreather mouth peices have a valve (called an ADV) that the diver turns to go from the rebreather to some sort of alternate breathing source. This same valve should be turned when ever the mouth piece is out of the divers mouth and that will prevent water from entering the return hose to the unit.

It is possible, and has happened, where the diver either forgot to colse the ADV and the rebreather floods. This is really bad because the diver is now very negatively buoyant and just dropping ones weights might not return the diver to neutral or positive buoyancy.

the adv is the auto dil valve and is nothing to do with the dsv or bov

[Cave Diver]

Good catch!