A dealer will sometimes say you have two choices in a restricted district: live with hard water, or buy a “salt-free softener.” That is a false pair. The third machine is the one the ordinances keep naming: a portable-exchange tank.
What the tank actually does
The chemistry is the same as a brine-tank softener. Resin takes calcium and magnesium out of the water. That is softening. Health and Safety Code § 116780(h) defines regeneration as renewing that hardness-removal capacity with a sodium- or potassium-chloride brine, then a rinse.
The difference is where the brine is made.
On a self-regenerating unit, salt sits in a tank in the garage. On a timer or a meter, the valve dumps brine through the resin and sends a chloride-rich waste to a drain — laundry sink, cleanout, or floor drain. That waste is what Water Code § 13148(h) means by a residential self-regenerating water softener: equipment that discharges brine into a community sewer system.
On a portable-exchange service, the resin lives in a bottle or tank the vendor hauls away. Regeneration happens at a plant. No salt bags at the house. No brine line at the cleanout. § 116785(a) is the statewide install path that already names this setup: the appliance may be installed if “the regeneration of the appliance is performed at a nonresidential facility separate from the location of the residence where the appliance is used.”
A hardness test after a working exchange tank should drop. If a salesperson’s kit “shows zero grains” after a salt-free pitcher demo, that is not this machine. See what salt-free units are not.
What the state statute actually says
Water Code § 13148(g) is one sentence:
This section does not limit the use of portable exchange water softening appliances or limit the authority of a local agency to regulate the discharge from a centralized portable exchange tank servicing facility into the community sewer system.
Two halves. The first is why exchange tanks keep showing up as the written exception to local install bans. The second is why a “statewide always legal” claim is still wrong: the plant that regenerates those tanks can be regulated at the sewer, and a city, district, HOA, or CC&R can still have its own rule. § 13148 is an authorization for certain local sewer and recycling agencies after a regional-board finding. It is not a permit taped to your tank. Read whether softeners are banned in California for the district map. Check the legality tool for the city file we have.
Two local exceptions we opened
These are sewer-side carve-outs already on TapMatch city pages. They are not a California list, and they do not invent hardness.
Newman. Municipal Code § 11.06.060(M) (Ord. 2019-7 § 2): subsection (L)’s install-and-replace ban “shall not apply to water softeners that use exchange tanks that are regenerated off site at a lawfully regulated location.” It also carves out filtration, activated carbon, reverse osmosis, and non-salt conditioning units. City page: Newman.
Dixon. Chapter 14.01, Article XI, Finding EE (Ord. 12-004): residents “shall maintain the ability to soften or condition their water by using water softening or conditioning appliances that do not discharge brine to the POTW. Among these are portable exchange water softeners, which use a removable tank to hold the ion-exchange conditioning material. The ion-exchange tank is removed by a vendor and is ‘regenerated’ with brine at a facility outside the City of Dixon where brine discharges are allowed.” City page: Dixon.
Other files on this site print the same idea in different words (IEUA “portable exchange … regenerated off-site,” Sunnyslope “portable cartridges,” Paso Robles “portable exchange tank system,” San Juan Bautista Chapter 5-36 Finding Q). Open the city page. Do not treat this paragraph as the ordinance.
Three machines people flatten into “softener”
Self-regenerating salt softener. Ion exchange. Brine to the house drain. The unit most local sewer rules restrict.
Portable-exchange / off-site regeneration. Ion exchange. Brine at the plant. The usual written exception where the rule is about sewer discharge, not about hardness removal.
Salt-free / TAC conditioner. Not ion exchange. Hardness stays in the water. No brine line because there is no regeneration. It is not a portable-exchange substitute if you want soft water.
Ask the vendor three questions: Does the resin leave the house? Where is the salt applied? Is there a drain line to my sewer? If the answers are “no, in the garage, yes,” you are looking at a self-regenerating unit no matter what the brochure says.
What this page does not do
It does not pick a vendor, a rental price, or a tank size. It does not invent NSF listings or grains. It does not say portable-exchange is legal on every California sewer, every septic, or every HOA. Confirm the agency on the sewer bill — and the plant the vendor uses, if the district cares about that discharge too.