Plumbing Fixture Flow Rates

[sefnfot]

What is the shower flow rate for Santa Monica, CA starting July 2018?
I found this story that puts it at 1.8 gpm while I can only find the pdf listed below on the city website.
This story

the city website pdf

[Jerry Peck - Codeman]

I was able to reach my man in California, he will be able to answer your question better than I can.

My apologies for the delay in getting back to your question.

[GunnarAlquist]

Hiya sefnfot,

The enforcement of codes in California gets a bit complicated. As of January 1, 2017, California has been enforcing the 2016 California Building Standards Code which incorporates the 2016 California Plumbing Code (a modified version of the 2015 Uniform Plumbing Code) and the 2016 Green Building Standards Code. The 2016 Codes should be enforced until the 2019 Codes are adopted by the state beginning January 1, 2020.

Clear as mud?

Shower flow rates are covered in the Green Code rather than the Plumbing Code (the relevent section is below). Until 2020, the shower flow rate will stay at 2.0 gpm.

In addition, the way I read the code, it looks like 2.0 gpm is the maximum allowable flow rate for the entire shower, no matter how many showerheads or valves are present. However, I often see multiple shower valves in stall showers, so some jurisdictions may not be enforcing this part of the Green Code. It would be best to ask someone at the city to make sure.

The article that you reference is from 2015, so I can't imagine the author has the ability to see that far into the future, unless they have some inside information. To the best of my knowledge, the 2019 Code has not been published.

Another possibility may be that Santa Monica has a local regulation that is tighter than California's. I visited the City of Santa Monica's website, but could find no local ordinances regarding shower water flow rates. The only thing that I can think of is to check with their building/permit office and ask if they have a local ordinance that requires a lower flow rate.

Gunnar

Below is from the 2016 Green Building Standards Code:
4.303.1.3 Showerheads.
4.303.1.3.1 Single showerhead. Showerheads shall have a maximum flow rate of not more than 2.0 gallons per minute at 80 psi. Showerheads shall be certified to the performance criteria of the U.S. EPA WaterSense Specification for Showerheads.

4.303.1.3.2 Multiple showerheads serving one shower. When a shower is served by more than one showerhead, the combined flow rate of all showerheads and/or other shower outlets controlled by a single valve shall not exceed 2.0 gallons per minute at 80 psi, or the shower shall be designed to allow only one shower outlet to be in operation at a time.
Note: A hand-held shower shall be considered a showerhead.

[GunnarAlquist]

Or, I may be incorrect about the limit for the entire shower.

Jerry and I have been discussing the wording of this particular code and the code is worded in such a way that it may allow more than one valve in a shower. This would then allow 2.0 gpm per valve. Since the intent of this particular code is water efficiency, it seems to me that the limit would apply to the entire shower. However, the wording does not support my conclusion and would explain why multiple shower valves are installed in large showers.

[GunnarAlquist]

Ok, further research and I now have clarification. Frankly, I let this go until tonight, but I had not thought to search for this particular document.

The state of California has published "Guide to the 2013 California Green Building Standards Code (Residential)". Yes, there is a nonresidential version. This document is similar to the NEC Handbook in that it contains the code and then an explanation. Currently, the guide to the 2016 is "Forthcoming" according to the CA.gov website, but 4.303.1.3 is worded the same in 2013 and 2016, so I am going to assume that the interpretation is the same.

Anyway, from the "Guide to the 2013 Green Building Standards Code (Residential):

Section 4.303.1.3.2 addressing multiple showerheads has been carried forward from the 2010 CALGreen with revision to reference a specific water flow rate. The specified flow rate of 2.0 gallons per minute at 80 psi also applies in situations where one or more valves supply multiple showerheads in a single shower enclosure or space.
"Fixture types" or sources of water flow include but are not limited to showerheads, handshowers and bodysprayers.

The maximum flow rate provisions apply to the total amount of water flow resulting from each valve supplying the individual shower enclosure regardless of the number of attached showerheads (or similar fixture outlets or sprays). For example, if only one valve supplies a shower enclosure or shower area, the maximum water flow, regardless of the number of showerheads and other outlets, is 2.0 gpm @ 80 psi. If two (or more) separate valves provide water to separate showerheads and other outlets, the maximum flow rate for each valve would be 2.0 gpm @ 80 psi. If the operation of two or more showerheads and body sprays controlled by a single valve results in more than 2.0 gpm @ 80 psi total water flow, then only one showerhead may operate at one time with a maximum flow rate of not more than 2.0 gpm.

This is different from my original interpretation. I had assumed that the intent was to limit the water usage for each shower enclosure. But, it seems that you can get around the water flow limitation by installing multiple shower valves, even if the shower enclosure is for a single occupant. Other than circumventing water usage, if enough valves were installed in a shower, the incoming water flow could (at least theoretically) exceed the ability of the drain to remove the water from the shower, resulting in overflow of the pan. There may be a limit as to how many valves you can install in a specific volume or space, but I have yet to find it.

I will keep looking.