How to choose a good plumber,
Use only licensed & insured plumbers, don't just take their word for it, call and make sure they really are licensed and insured, 919-875-3612, or www.nclicensing.org/OnlineReg.htm.
Check to see if a permit is required, quality plumbers will want to pull a permit to protect everyone, it usually cost about $70 and should be included in the price, this is the plumbers responsibility not the homeowners, & if the homeowner pulls the permit the homeowner is responsible, if the plumber pulls the permit the plumber is responsible.
Most plumbing requires a licensed plumber by law, for example changing bathroom faucets do not require a licensed plumber, but changing a toilet, shower valve, shut off valve, repairing a leak in a yard or behind a wall, or any plumbing behind a wall, any plumbing underground, hose bibs, installing a water filter, tubs, showers, well pump, and most other common plumbing repairs, if you have a question you should call your town.
Information on the need of a licensed plumber can be found from the city inspection department, here are a few numbers, if your jurisdiction is not listed then go to www.wakegov.com/inspect/jurisdiction.htm.
Wake county, 919-856-6060
Raleigh city limits, 919-516-2495
Type company name and "reviews" in Google, also type only the phone number in Google, some companies run their business in the ground and simply change their name to get away from their bad reputation.
Check insurance info, call the company and confirm it's still active.
Remember you get what you pay for, if you get three estimates for the same work and two of them are $1500 and 1 is $500 there is probably a reason one is alot cheaper.
Make sure when comparing estimated you are comparing apples to apples, & get estimates in writing.
Use QUALITY materials, this makes alot of difference, for example pex pipe is a little more expensive than cpvc pipe, but in my opinion cpvc is not quality material, I certainly don't use it. I would also try to install Moen or Delta faucets and valves, you can't go wrong with quality.
If u can't find any info on your plumber on Google, it may be a bad sign.
Get a warranty in writing.
Call the Better business bureau and look into complaint history, but keep in mind there are several companies that are members of the B.B.B., have several complaints and somehow still have a good rating, if complaints by customers don't give you a lesser rating I have to wonder what does?
Get a price in writing before any work is done so you know the price won't change.