If you're not familiar with plumbing components and costs, it's easy to fall victim to a scam. You can avoid these common plumbing scams by doing research before hiring a plumber, and learning what to expect from a professional.

1. Get three estimates

Seek out three detailed estimates before hiring a plumber. Be leery of any contractor who is willing to give a quote over the phone, because the plumber needs to be able to see the job site to assess damage and any obstacles that may raise costs. Do not accept a verbal contract because it can be difficult to enforce.

If one of the bids is much lower than the others, it could signal a potential problem. A common plumbing scam is to give a low estimate that doesn't account for all of the labor needed. You will then need to pay for the additional labor before the plumber finishes the job, putting you in a tough situation.

2. Avoid the high down payment

Nearly all contractors require some type of down payment before starting a job. Most professionals charge around 10 percent, but if the plumber asks for a significantly larger down payment, you should be cautious. The plumber could take your money and run.

3. Watch out for theft

A common scam involving rentals or apartment buildings is when a plumber informs you that he was sent on behalf of the building owner. Or, the plumber will say the water department sent him to check the main water line and make necessary repairs. Once you let him in your home, he will look for valuable items to steal. Don't let any contractor enter your home without first verifying his identity with your landlord, building supervisor or the water company.

4. Bait and switch

In the price quote, the plumber should give you the make and model of all major parts or appliances. A common scam is to charge for expensive parts, but use cheaper parts and pocket the difference. If you feel the price of an item is too high, call your local building supply store to compare prices.