Home improvement stores have many plumbing products in stock these days making it easier for you to estimate how much a potential plumbing project might cost.
All you need to do to figure out basic plumbing costs is go to a Home Depot or a Lowes store and price out the parts needing to be repaired or replaced. So based on that assessment, you should be able to get a really good idea how much the materials will cost.
As far as the labor is concerned, a typical plumbing rate is $75 to $100 an hour. So if this is the kind of job where you need to hire a plumber, then those are fairly good numbers to estimate the labor for the project. Try and figure out how much time the installation or repair work might take a plumber to complete, and multiply that by the cost per hour for the plumbing professional.
Most plumbing companies offer free estimates, and will come out to the work site to do that. Some companies might use flat rate pricing, but either way they should send their serviceman out to the job site for the estimate. You can decide to have them do the job for you or not based on that price. You might want to ask if there is a call out charge for the estimate before you ask them to come.
So that’s a general guide of how to estimate costs. It’s good to have a basic idea in mind in case someone is trying to take advantage of the situation and pull the wool over your eyes. If the estimate is way off the mark, it’s possible you overlooked something, in which case the plumber should explain why there’s a discrepancy.