Percent of Occupants

Hi Amy, the percent will vary depending on what's going on in your building, but I think the main trick here (related to flush fixtures anyway) is to remember to use the % of occupants within each gender. For example, teams often use 50% for urinals because women don't use them. But it should be 100% if all males have access to the urinal. That said, if you have urinals with different flush rates and only a portion of males have access to the different rates, then you'd need to adjust the %. The same logic applies to kitchen sinks but without the gender component.

Follow up question to the original question, there are two places on the Water Use Calculator where they ask for "Percent of Occupants" when dealing with urinals. If urinals are not in all of the male restrooms, do you only adjust the "Percent of males expected to use restrooms with urinals" field at the top of calculator OR do you need to adjust this percentage in the Fixture Flush table in the Calculator as well? The fixture flush table also requires Percent of Occupants, do you leave these as 100% because you already adjusted it above for the percent of male access to restrooms with urinals?

The percentage column within the Fixture Flush Table is really supposed to be used to indicate a breakdown if you have fixtures of different flow rates (like if you had some urinals with 0.125 gpf and some with 0.5 gpf). You'd adjust the main "Percentage of Males w/ Urinals" cell at the top to indicate your best-guess for how many males overall will use/access restrooms with urinals (maybe 90% if there are very few unisex/non-urinal restrooms). You then would break just the males between the two different urinals listed on the calculation (maybe 75% for the 0.125 gpf fixtures and 25% for the 0.5 gpf). The only time I've really had to use it was in a renovation+addition project where some restrooms were completely new and some were existing. If all your fixtures have the same flush/flow rate, that in-table column will always be 100%.

Awesome explanation, I really thank you Kristina! i seem to get confused every single time and your explanation the flush table is particularly helpful. got it. thanks. in my case, we have same flush rate, so i will keep it as 100% in the flush table, but adjust the percent of males at the top of the calculator only.

Hi In regards to the "Percentage of Occupants" and showers, how should this be implied. We are designing a huge office building where there will be showers available for people arriving on bikes or working out. The percentage of people acutally using this facility will be very limited compared to the total occupancy level of 3400 people. Since everyone has access to this, should we then still put 100%? Kind regards, Lise

Hi Lisa,  I had a lengthy discussion with GBCI over this calculator in order to get a full understanding of what they expect to see. For your situation, where all occupants have access, yes, the % should be 100. The calculator already assumes that a small number of people will actually use them. If you look at the default daily uses and other built-in calcs in the tool, you can probably tell what they do.  If you had a project where only a portion of the occupants had access, you could then adjust the % down accordingly, and provide a separate narrative explaining your assumption so that the reviewers know why it is something other than 100%.

Hi Kristina, just came across your explanation today, which I complete agree but I am observing a small glitch here in the calculator.If I put 0% for the urinal in the top row (for project with no urinal), then input values for urinal (drop down) in the flow fixture table should be greyed out or non editable or 0% which is not the case....??

Here's another possible case where we need to break down Urinals based on whether they're in a Gender-free (GF) restroom, which are becoming increasingly common on campus, or a male-only restroom. Same metered, low flow rate but different % of male occupants with access: 50% for GF; 100% for single sex. Does that make sense with the Calculator, which also befuddles me every time.

I think the best approach there, since your fixtures aren't different between the male / all-gender restrooms, would be to adjust the % of male occupants with urinal access at the top of the form and let the form automatically adjust the uses.   Could be pretty simple - take [the number of male + all-gender restrooms with urinals] over [the total number of male + all-gender restrooms] and make that your percentage of male occupants with access to urinals. Then just list each fixture once as you normally would and the calculator will adjust the total uses based on that percentage. No need to separately adjust the percent of occupants lower down.   Could get more complex if you have different flush rates in different restrooms, or a layout that determines access (e.g. a staff area with M/F restrooms and a student area with only all-gender restrooms) but in most cases a simple percentage based on your restroom count will give the calculator enough information to give you an accurate output.

Great, comprehensive answer, Emily.  I will make & document logical assumptions re: the layout that determines access. Budget issues may eliminate urinals in the all-gender restrooms anyway.

No problem! Like Kristina said, the "percent of occupants" really only comes into play if you have fixtures with different flush/flow rates. In the vast majority of projects, you won't need to think about that column at all.