While talking with the gang, Howard proudly announces that his space toilet is being deployed on the Space Station International Space Station. After going over the schematics, he realizes he made a "teeny-tiny" mistake on the specifications for the diverter valve, that will cause the toilet fail after about ten flushes. Knowing his career is at stake, he gets Sheldon and Raj to help him find a way to reinforce the structure so the waste material avoids the spinning turbine (keeping waste away from the fan).
Raj suggests using two-inch PVC reinforcing the center cross-support. Once Howard says that it is no good, Raj recommends instead of trying to reinforce the structure, they just run another line, bypass it entirely. Sheldon points out it won't work as the diameter of the tubing is insufficient. Then, Raj asks if they could reposition the collection tank, but Howard reveals there is no way to mount it. Similarly, Howard wants to wedge a little piece of PVC behind the support rod, though, Sheldon informs Wolowitz he's overestimating the tensile strength of the substructure he is building. Raj shows another item instead of the PVC to keep the transverse filter assembly in place, without understanding that it is not a spare part on the Space Station but is rather the plastic device used to keep the cheese from coming in contact with the lid of the pizza box. They eventually test a prototype and Howard notifies NASA with the solution, yet the space toilet apparently still fails. The entire space station crew takes an unscheduled space walk to escape the space station.
During Howard's sixth season visit to the ISS, the more experienced crew makes him clean out their space toilet which could be his system.