Start with a site visit, not a phone price
Plumbing jobs hide behind walls, under slabs and in crawl spaces. The price for "replace a water heater" changes completely if the venting doesn't meet current code, the gas line is undersized or the unit sits in a cramped attic.
On the visit, note:
- Fixture count and locations for remodels and repipes.
- Pipe material you're tying into (copper, galvanized, PEX, CPVC) and its condition.
- Access: open basement, finished ceiling, slab, crawl space.
- Code items the inspector will check: venting, expansion tank, strapping, clearances.
- Water pressure reading, if you're touching the supply.
Price by fixture or by task
New construction and remodels are often priced per fixture: each sink, toilet, tub or appliance connection gets a rough-in price and a trim-out price. It's fast to calculate and easy for a general contractor to compare.
Replacements and repairs are clearer by task: remove old unit, supply and install new, add expansion tank, permit. Each line maps to something the homeowner can picture.
Either way, separate fixtures the client supplies from fixtures you supply. If the homeowner buys their own faucet, say so, and say that your warranty covers your labor, not their part.
Allowances, access and permits
Use allowances for work you can't confirm until you open things up: corroded fittings beyond the work area, venting corrections the inspector may ask for, slab leak repairs. Show a ceiling amount and bill only what's used.
Access is its own line. Cutting a 2 × 2 ft opening in drywall and patching it afterward is real work; if you don't do patching, write that the client arranges it.
Permits belong on the estimate, not as a surprise on the invoice. Many cities require one for water heaters and any rerouting of supply or drain lines.
Validity, deposits and turning it into a job
Copper and fixture prices move, so 14 days is a common validity window for plumbing work. Emergency work is usually priced on the spot, but anything planned deserves a written estimate.
Deposit rules depend on your state. California, for example, limits home improvement down payments to $1,000 or 10% of the contract, whichever is less. When the work is finished and inspected, convert the estimate to your plumbing invoice and adjust any allowance lines to what was actually used.
Giving options: good, better, best
For replacements, many homeowners appreciate choices. Put two or three versions on the estimate: a standard 50-gallon tank, a high-efficiency tank, and a tankless unit with the gas line upgrade it may need. Each option shows its own install price, so the customer can weigh upfront cost against running cost and warranty length.
Mark options clearly ("Option A", "Option B") and say in the notes that the customer picks one. Before you convert the estimate into an invoice, remove the options they didn't choose so the totals line up with the work done.
Last checked October 23, 2026.