Mark
I think as Mike said if your that worried about water getting into the loop if you bailed of loop including the oc side & went to a stage reg .Then to prove it to yourself that the water is not going to get in then you need a big bucket or leybourne ! isolate & purge oc reg, put your head under water ,suck neg turn knob release mouth piece under water ,return head to air & breath

keep mouth piece under water untill you are either happy that it is holding neg in water or the neg fails .if it fails then open loop & see if it is flooded or if the gas leak is somewere else
hope that helps m8
see pm
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Colin
I trust my rebreather completely ,
I just don't trust the user
onwards & downwards