Rainwater Harvesting Regulation

Now that I am harvesting rainwater, there is an app for that. Just kidding. Actually, there is a regulation for that.

As part of the CPC 2013 (California Plumbing Code). There are regulations and limits on rainwater catchment systems effective 1/1/2014.

First, the rainwater system must be isolated from the potable water supply, by either air, or a backflow prevention device.  I intend to put a backflow prevention device in when I connect the storage tanks to the underground irrigation system, since the irrigation system is connected to the potable water supply.

Next, there seem to be restrictions on the ability to use the rainwater in a spray irrigation system. The concern here is to prevent pathogens from being released into the air where they might infect someone.  There seems to be a workaround if the filtration level is sufficient. Apparently 100 micron filtration will do it.  I am going to that level of filtration anyway to insure that I do not clog the spray heads of the irrigation system.

There is also a restriction on the maximum amount of storage in a tank. Apparently 5000 gallons is the maximum storage per tank without a building permit.  Since I intend to pump the rainwater harvested back through my irrigation system and I intend to have more than 5000 gallons of storage, but not more than that in any one tank.  For a citation on CPC 2013 requirements  see this website.

After talking with the county building department I was informed that I must secure a plumbing permit at a nominal cost before I do the job. They have asked that I submit a plan to them for the project.  I suppose I will print out many of the illustrations I have already made for this blog as part of the plan. Apparently I am the first person to even ask about this stuff. No one has sought a permit for this use previously.

April 3. Today, I had a building inspector here for the final inspection of my deck. I passed with flying colors. (After all, it was the installation of the deck that started me on this path.  I rerouted the downspouts to the valve so that water could be diverted to the storage tanks.) He informed me that I should NOT file for a plumbing permit and that I should just put it in and not worry about it. Now I have an answer that I like. He confirmed that the restriction on 5000 gallons for a permit is per tank, not per system.


last modified 4/5/14