Yesterday when doing my evening routine I thought about placing a heat exchanger in a flush. My rig is placed less than 2m (in straight line) from the toilet (bedroom en suit) and I can't see ANY major drawback of this idea

PROS:
- water has much larger heat capacity than air,
- water will conduct heat much more efficiently than air,
- in a flush it would be exchanged regularly - and if not still there is 8-10l o water,
- placing small turbine in a flush is not a problem,
- noise reduction ( no fans working in a case),
- it could be set up as additional cooling loop for the existing "ordinary" WC system.

CONS:
- heat exchanger itself, can't be just a radiator due to oxidation,
- home-made exchanger (copper pipes + some copper fins) will cause radical pressure drop ->
- required second pump means more noise,
- ... ?


Any opinions? Will that make sense (it is not important really)? It would be cheap-o, buying list would be short: copper pipes+copper sheets for "fins"+tubes+extra pump+extra reservoir.