A long time ago I worked for a sparky/plumber/septic installer.We worked for a builder who would have us,as soon as the basement slab was poured,andif there was a bath in the basement,have us set a toilet. He would then build a small temp enclosure around it. Water supply was a water hose. In the winter,we used r.v. antifreeze to prevent freezing in the winter. The first time the county ahj saw one of these he says"I should probably make you tear it down, but wait I've got to go" He never said another word about this arrangement.Btw this was before the days when porta johns were readily available in these parts.