"It's not just the amount of water per faucet, but the amount of water per shower space."

Correct: Here's the rule:

"California does allow more than one showerhead to operate at the same time, but only under strict flow‑rate limits. If the combined flow of all simultaneously operating outlets exceeds 1.8 gallons per minute (GPM) at 80 psi, then the system must be designed so that only one outlet can run at a time."

Nearly all California-compatible shower heads have flow rates of 1.5, 1.75, and 1.8 gpm. Nearly all California-compatible hand showers have flow rates of 1.75 or 1.8 gpm. Even 1.5 + 1.75 >= 1.8 so you need a diverter to switch between the shower head and hand shower.

Most hand-held shower units attached to a shower head have a diverter, so only one head gets water at a time. It's like the thing that you pull to get the shower instead of the tub. One of the reasons this is standard is that the vast majority of showers don't have the flow to have both going at the same time because they come from one pipe.

I think that you are asking to have two completely different sets of controls in a single shower. That is, you want a fixed showerhead and handheld on one side of the shower and a separate handheld on the other side of the shower. That is not allowed in California (unless it's one of those "gang" style showers they had in my high school gym).

All showerheads within a shower need to be controlled by the same volume control and temperature control. A diverter is used to select the showerhead.

For example, see the attached photo of my primary shower (Samuel Heath controls with Hansgrohe showerheads). The top lever is the diverter. The center lever controls the volume (on/off), and the bottom lever controls temperature (thermostatic value). The wall-mounted fixed jet showerhead is on the opposite wall. And I have a rain head in the ceiling.

The second photo below shows my hall bathroom remodel (before waterproofing and tile). The copper pipes coming up from the floor bring hot and cold water to the brass shower valve in the center (combination of volume, thermostatic, and diverter control). The thermostatic valve mixes hot and cold water to the selected temperature and sends it to the selected output. This is a non-sharing valve from California Faucets.

The "nipple" on top will be replaced with a fixed showerhead. The "nipple" to the right of the shower valve will be replaced by an "elbow" that connects with a hose to a handheld.

If I were to add another set of pipes and valves on the opposite side of the shower, it would not meet California code. [Edited to add that I had to change the shower drain to a different brand as it was too close to the wall.]

You need a diverter in CA, as you can only run one shower head at a time in one shower.

Some people will pass the permitting inspections and then have things "fixed".

The only way that you can do what you want is to have a single diverter control all the water outputs inside the shower, or you create the space as two clear separate distinct showers. Meaning a partition between the areas. You can not have a single shower with multiple independently controlled water sources. This is also why drain size is controlled. Multiple water sources on at once will overwhelm a drain and lead to flooding.

I had to deal with CA code when we lived there, but I was glad to have more options when we built in FL.

No issues with multiple water sources in our shower in FL, or with the drain. Here we can have multiple water sources that are independently controlled. I like to add a volume control to each water source and not just an on/off control. I was also glad we didn't have to have the lowest volume toilets here in FL, so we get a decent single flush and you aren't forced to have to flush twice!

Hi, This is a true story of buracats in action.

I get a work order that a tenant's shower is cold. I drive out there and the unit is a tub shower.

I turn on the shower hot only and the water out of the shower is cold. I turn the valve from shower to tub, the water is hot. I take the shower head off and then run hot water to the shower, with no shower head the water is hot. I drilled out the holes in the shower head a little bigger, miracle hot water.

Good Luck Woodbutcher

" Hi, This is a true story of buracats in action. "

I have to disagree - this is a story of poor design and bad workmanship.

This is a classic issue of a long run from a water heater on one end of the house and a bathroom, usually the master bath on the other end. Often the supply lines are in the slab, and they aren't insulated or have minimal insulation. There's no return loop for a circulating pump. So, at 1.8 gpm, the heat is entirely disapated to the slab before it comes out of the shower.

The other possibility is a tankless water heater that has too high of a required flow rate to activate it or keep it running. Sometimes people set the temp on the tankless too high (no reason to do anything more than 120 - 125) so by the time it mixes down, there isn't enough flow through the heater to keep it activated.

Neither one of those issues should be blamed on buracrats.

@ wdccruise has the interpretation of code right. Inspectors are looking for the type of "creative reading" of the code you are suggesting. It's not worth having to redo the work.

California, like much of the west and south west, doesn't have enough water for people to be stupid about it. Same in Arizona, Colorado, New Mexico, Nevada, etc. If you really can't abide by reasonable water use codes, move to someplace that isn't a desert.