How to charge for plumbing work is a question with three honest answers, and most shops use all three: flat rate for the tasks the price book holds, hourly for the diagnosis and the open-ended job, and a stated fee for the call-out or the diagnostic visit. What matters more than the choice is that the basis is on the estimate and the same basis is on the invoice. The flat rate pricing tool on this site builds the task prices from your costs, and the invoice tool prints them the same way the estimate did.
Flat rate for the known task
A water heater swap, a faucet replacement, a disposal install: each takes a known number of hours and a known list of parts, so it gets a price before the work starts. The customer decides on a number; the technician's speed is the shop's margin. The price book template on this site holds the prices the flat rate tool builds.
Hourly for the unknown
Finding the leak, clearing the drain that will not clear, the job that opens a wall. The customer is told the rate and the estimate of hours, and the invoice shows the hours worked. Charging flat rate for the unknown is how a shop loses money on its hardest jobs.
The call-out and the diagnostic
A stated fee to attend, and a stated fee to diagnose, each on the estimate before the visit, and each either credited against the work if it goes ahead or charged if it does not. The fee that surprises the customer at the door is the one that is disputed.
The same basis on the invoice
The invoice shows the flat-rate task at the estimated price, the hourly work at the rate and hours, the fees as lines, the deposit deducted. The invoice tool on this site prints that; RoughInDesk Pro prints it from the accepted estimate so the basis cannot change between the two.
Questions people ask about how to charge for plumbing work
Should I tell the customer my hourly rate?
When the work is hourly, yes, before it starts. For flat-rate work the customer buys the task price, not the rate.
What if the flat-rate job takes longer?
The shop absorbs it, and the price book is revised if it happens often. That is the trade the customer made for a fixed price.
Is the tool free?
Yes: the flat rate pricing, price book and invoice tools work without an account.