Bad to get a breath on a regulator with closed valve?

[dlofting]

My exhaust valve was doubled over. Didn't discover it until I tried to descend and got a mouthful of water. Take your second stage apart and check the diaphragm and exhaust valve. Look for any cracks in the housing or tears in the mouthpiece.

 

[broncobowsher]

In case you missed it, the first stage needs to be capped. Either a sealing dust cap or attached to a tank with the valve turned off. If it is just open you can suck a little air through both stages. That isn't a leak, that is the regulators trying to deliver air without enough pressure pushing through it.