Having read this, I'm strongly considering routing my bath and shower wastes through a poorly insulated hot water cylinder in reverse (new [warm] waste in at th

Having read this, I'm strongly considering routing my bath and shower wastes through a poorly insulated hot water cylinder in reverse (new [warm] waste in at the top, old cold waste out the bottom). Hot water will float in there. Cold will be displaced first. It only has to hold the volume of "a shower" and we'd keep that energy within the envelope of the house, without added humidity or state-change heat loss. The only major downside is the "what happens when it clogs" question. To work normally, it would require the discharge to rise to the same height as the top inlet before falling to the drain, but there could be a secondary purge for pressure-flushing it once a month. Rarely does plumbing make so much sense to me. I suspect I'm overlooking something. Answers on a postcard.