How were the trash and sewage removed from the boat?

In WW2, trash, including garbage, were usually thrown over the side when at sea for an extended time. The trash was bagged and weighted so that it would sink to the bottom. The objective was to be sure that the trash didn’t give away the boat’s identity or location. This also meant that someone had to come up on deck the throw the trash over the side. That could be dangerous and in heavy seas the trash would have been retained in the boat until the seas calmed.

For sewage, we are talking about the human waste that goes through the heads (toilets).The sanitary tanks for three of the heads were emptied overboard each morning, usually between 05:00 and 06:00.High pressure air is used to blow the tanks dry. This is done by the auxiliaryman who is part of the engineering department. It is critical that the sanitary tanks then be vented to eliminate air pressure. Failure to do so results in a very nasty surprise to the next person flushing the head.

The head in the after torpedo room is different. This head flushes directly overboard since there is no room for a sanitary tank below the deck. (The propellor shafts are below that space.) The challenge is that the water level outside the boat is above the top of the torpedo tubes while the toilet is maybe a foot and a half off the deck. The toilet sits well below the outside water level. The issue then is: how do you flush a head uphill without the contents and seawater coming back into the boat? You do that by first moving the contents to a small intermediate tank.

It is a multi-step process to flush this head. And if you get it wrong, you get to clean up the mess. The basic process is:

1. Ensure that the bowl flapper valve is shut
2. Add water to the bowl through the sea and stop valves
3. Shut both valves
4. After using the head, operate the flapper valve to empty the contents of the bowl into the intermediate chamber
5. Shut the flapper valve
6. Charge the volume tank until the pressure is 10 pounds higher than the sea pressure
7. Open the gate and plug valves on the discharge line
8. Operate the rocker valve to discharge the contents of the expulsion chamber overboard.
9. Shut the gate and plug valves.
10. Vent any remaining pressure.

The process works but is not for the faint of heart. By the way, this head would only have been used when on the surface and not at all when in port.

Current environmental regulations require that ships no longer discharge waste into harbors. Therefore, modern submarines need to have holding tanks for all heads and a means to discharge the tanks to a sewage treatment system when in port.