· Michael Blair
Metro Nashville requires a permit for more plumbing work than most homeowners expect, and the line is not where common sense puts it. The rule of thumb that works: replacing a fixture in place is usually yours, and anything that alters the pipes in the walls is not.
Work that generally needs a permit
Anything that changes the plumbing system rather than the thing attached to the end of it. New or relocated drain, waste and vent lines. Water heater replacement, including a like-for-like swap, because it involves gas or a dedicated circuit and a relief discharge. Repiping. Sewer lateral repair or replacement. Adding a bathroom, a wet bar or an outdoor kitchen.
- Water heater replacement, tank or tankless
- New or moved drain, waste or vent piping
- Whole or partial repiping
- Sewer lateral repair, lining or replacement
- Any new fixture that needs a new drain
- Gas line work of any kind
Work that generally does not
Straight replacement of a fixture where the existing supply and drain stay exactly where they are. A faucet, a toilet on the same flange, a garbage disposal, a shower head, a supply line, a shut-off valve. Clearing a blockage is maintenance and needs nothing.
The moment a replacement involves moving the drain even a few inches, or converting a tub to a shower with a different drain position, it stops being a swap and starts being an alteration.
Why the inspection is the part that matters
A permit is not a fee for permission. It buys an inspection at the stages where the work is about to be covered up, which is the only point at which a mistake is cheap. Rough-in is inspected before drywall; a slab job is inspected before the pour.
A contractor who suggests skipping the permit to save you money is saving themselves the inspection, not saving you the fee. That is the single clearest signal you are dealing with the wrong firm.
What unpermitted work costs you later
It surfaces at closing. A buyer’s inspector finds a water heater with no permit history or a bathroom that does not appear on the property record, and the work becomes a negotiating item at the worst possible moment. Retroactive permitting means opening finished walls so an inspector can see what is behind them.
Insurance is the other exposure. If unpermitted work contributes to a loss, a carrier is within its rights to look closely at whether the installation met code, and you have no inspection record to point at.