We are working on a CI project that changed the toilets only few years ago with 6lpf. Less than 3 years.

We can not change only the tank of these toilets so we would have to change it all.

We installed very low flow fixtures everywhere: urinals changed to 1.89 lpf, 1.89 lpm kitchen sinks, 1.3 lpm bathroom sinks and 5.7 lpm showers. Despite all these efforts, it is impossible to obtain 25% savings (we have 24,48%).

The owner of the building thinks it's ridiculous to change the toilets that have just been changed and we do not quite disagree with his point. In addition, the plumber told us that the building piping is not designed to receive less water and that this could create a lot of clogging problem and even breakage.

Is there any way we can reach 25%? 

Thank you!