We replaced our household toilets with 1.6 gallons/flush models (they will all be 1.3 gpf soon) this spring due to worries about our well. Some observations:
- I was concerned our old DWV system would not handle the lower volume efficiently. Turned out to be just fine.
- The flush mechanism is whole 'nother model from the flapper-and-float workings of yore.
- Many of the new models are "chair height". The jury is still out, IMHO.
- The new fixtures came with "slam-proof" seats and lids. If you have a 7-year old grandson, it's the biggest benefit of all.