non-potable water for wc and urinal flushing means the flow rate for potable water is zero, right?

Hello,

From my experience, I treat the non-potable water uses (generally flushing for urinals and water closets) as normal water source in the calculator (potable). While completing the form, you have to enter the non-potable water supply (page 2 of the form). This value is taken from the calculator (i.e. the Design flush volume of WC and urinals). The form then calculates the percent reduction from baseline with alternative water sources (%). You have to select your threshold based on this value.

Also don't forget a narrative that mentions the source of non-potable water, where it will be used (flushing, irrigation, process use, etc.) and any special circumstances/calculations. Basically make your design clear to the reviewer.

Edit - Dang! Posted a bit late.

Hello,

we are working on a project where the flush volume is compensated by non potable water. I can not seem to find the non-potable water supply option in the calculator. Can you please point it out? Also has the definition of non-potable water been revised? 

Thank you

Hi Cristina,

The non-potable definition has not been revised to my knowledge. It's listed at the end of the Prereq/Credit language, and also in the online glossary: https://www.usgbc.org/glossary?utm_source=website&utm_medium=article&utm...
 

nonpotable water
water that does not meet drinking water standards

On our projects where we had non-potable water use inside the building for the flush fixtures, we completed the calculator as we normally would for the Prereq/Credit; then for the Credit only, you submit separate calcs/narrative explaining/showing your calculations for the non-potable water use. You do not include that info for the Prereq, as the Prereq savings are based on fixtures, only.
The instructions for this calc are not in the Ref Guide language, but are in the supplemental Water Use Reduction Additional Guidance doc. Do be careful with the instructions there, though, as they conflict with what the v4 Ref Guide states about application to the Prereq. To be clear, alternative water use cannot be applied to the Prereq in v4; this is stated in the Ref Guide where they point out the changes from v2009. You can download the Additional Guidance doc under the Resources tab for this credit in the online Credit Library.