Many water treatment installations touch the supply line, the drain, or an electrical outlet. When they do, a local permit and inspection may be required. The rules depend on your city, county, and sometimes your water utility, so the first step is to ask the right office.
Step one: find out whether a permit applies
Call or visit the building department for your address and ask whether a plumbing permit is needed for a point-of-entry or point-of-use system, a new drain connection, or a change to the supply line. Ask whether an electrical permit applies if the system needs a new outlet. Get the answer in writing or on the department's website, and note the reference.
Step two: decide who files
In many places, the licensed installer applies for the permit and is listed as the contractor. In others, the homeowner applies. Confirm the arrangement before work starts. Ask who pays the fee, who schedules the inspection, and who receives the approval notice.
Step three: know the inspection stages
Inspectors often look at the work at more than one point. A rough-in inspection may happen before pipes are covered or walls are closed, so the inspector can see the connections, shutoff valves, bypass, and drain route. A final inspection happens after the system is installed. Ask the installer to schedule the rough-in visit before any wall or ceiling is closed.
Step four: check the items inspectors commonly look at
Ask the installer to confirm the bypass valve, the shutoff location, the backflow prevention device if one is required, the drain air gap or connection method, and the pressure relief arrangement where applicable. Check that the drain is connected in the way your local code allows, not just the way that is convenient for the installer.
If the inspector finds a problem
A correction notice is common and usually manageable. Ask who is responsible for the correction and whether it is covered in the quote. Get the reinspection date in writing and keep the notice until the final approval is recorded.
What to keep
Save the permit number, the inspection dates, the inspector's notes, and the final approval. Keep copies with the equipment manuals, because a buyer, insurer, or future service technician may ask for them. This process covers approvals only, so the day-of work itself is covered in other guides on this site.