You might not think much of it when you toss something in the toilet—after all, you’ve got a plunger handy, right?—but these seemingly innocent things can do irreparable damage to your home’s pipes. And while these types of fixes do not come cheap, the money may be the least of your problems if your home floods as a result.To help you avoid a costly headache, we asked a plumber to dish on the most dangerous things homeowners do.