Many years ago when I was a young sailor on HMCS/M Okanagan, an
Oberon-Class submarine, we had a similar experience. We had a 2500 gallon black-water tank, and when that filled up, it had to pumped outboard; when we were at depth, we used HP air at about 30psi over sea-pressure to push the black-water to sea. The first step in the procedure was to shut the valve isolating the tank from the line coming from the heads (toilets). The second step was to make a pipe (announcement) throughout the boat indicating that the heads were out of bounds.
On this particular day, we had a very junior outside engineer tasked with emptying the blackwater tank. The trimming officer (the person whose job it was to make the pipes) was a chap of Korean heritage with an accent so strong you could cut it with a knife. As luck would have it, the engineer forgot to isolate the tank, and Lt Tam forgot to make the pipe... someone used the heads and stepped on the flushing foot-pedal... a 2500 gallon blackwater tank charged with air at 30psi all of a sudden given a 2" escape pipe... the ensuing pipe became legendary in the annals of Canadian submarine history: "Hear though... no passage thwew contwol. Sh*t on deck!" (and everywhere else for that matter!