I've had an issue come up multiple times in the past few weeks that I hope in telling will prevent you from similar headaches. In multiple projects that I've been involved in, we have situations where 100% of the water used for landscaping is being supplied by non-potable sources, yet in every case we will not be earning the 2nd point (v2 rating systems) or the other 2 points (v3 rating systems) for WEc1, Water Efficient Landscaping... Why, you ask?
The issue with WEc1 is that the basic requirements listed in the rating system omit a very key statement which can only be found buried deep in the reference guides. Here I'm quoting from the LEED-NCv2.2 reference guide, but I checked and the v3 edition has the same problem:
"If the Percent Reduction of Potable Water is equal to or greater than 50%, WEc1.1 is earned."
So far, so good... nothing unexpected... but wait!
"If the Percent Reduction of Potable Water is 100%, you must also calculate the Percent Reduction of Total Water (Potable plus Reuse) according to Equation 7 […the long one where you have all the landscape coefficients and such]. If the Percent Reduction of Potable Water is 100% and the Percent reduction of Total Water is equal to or greater than 50%, WEc1.2 is earned in addition to WEc1.1.
The problem here is that the rating systems (the requirements you get to view for free) make no mention anywhere of the fact that TOTAL water use, not just potable, must be reduced by 50% along with the 100% potable water reduction in order to earn the additional point(s). It only shows up deep in the "Calculations" section of the reference guides...
If you have ample supply of non-potable water sources for a project, it is less likely that the design team has examined in detail the total water consumption of the landscaping as performing these calculations is time-consuming (read: costly).
Why this requirement isn’t stated upfront in the credit language is lost on me, but the fact remains we must not only reduce potable water use completely but also total water demand based on the LEED calculations. Had I recognized this before the latest update, I would certainly have suggested an amendment to the rating system during the public review. Let's all make an effort to correct this during public comments for the v4 rating systems!
Disagree with my interpretation? Did you slip one by a review team and get the extra points without anyone noticing? Let us know by leaving a comment!