Our project is in a 57-story building where the existing toilets are original to the building (1972) and are blow-out toilets at 3.5gpf. To replace the existing toilets and install a modern HET would require the wall to be opened up and the existing waste piping and carriers to be replaced and modified. This is a large expense to our project. We have located a 3-hole blow-out toilet at 1.6gpf that could be used to replace the existing toilet and get some pretty good savings. At the same time I have seen language in LEED's additional guidance docs that projects cannot get any savings from blow-out toilets. I feel that our project is meeting the intent of saving water but it just happens that our baseline/existing condition has toilets that unfortunately use a lot more water than current code. Any advice on how LEED would evaluate this?