1. Treating the garbage disposal like a trash compactor
Despite the name, not all garbage belongs in the disposals. Most garbage doesn't, yet some homeowners want to cram their waste down there until the blades stop turning. Watermelon rinds, potato peels, and pumpkin carvings are common items that plumbers and handymen have had to remove to free the blades. Say “garbage disposal” and people think they can put anything in there. Homeowners aren't always the problem. If you're having a house party, make sure your guests don't dump everything down there.
2. Placing too much weight on fixtures
Don't put weight on plumbing fixtures. That means not hanging heavy shampoo racks from showerheads or using the bathtub spout as a footrest. They are not made to have weight on them. It'll snap the showerhead right off at the threads.
3. Flushing household items or toys down the toilet
Every veteran plumber or handyman has a story about getting called to a home because the family flushed something inappropriate or bizarre down the toilet. I've seen everything from matchbox cars to tweezers to golf balls in the toilet. If the items get stuck in the trap, then the toilet has to be removed to retrieve them. Plunging can make the problem worse by pushing the item into the waste line.
4. Dumping construction materials down drains
You probably feel a great sense of accomplishment after completing a DIY project such as filling holes in walls or giving the room a new paint job. But you could have a new project on your hands if you dump building materials, such as the joint compound used for repairing walls, down the drain. Emptying into or cleaning construction materials in the sink can cause it to back up because the materials can harden in the drain and block it. Most of the time, the liquid goes down the drain and the solids stay behind. You're not going to get that out with a drain cleaner.
5. Cranking on a faucet handle
Repeat after me: Pushing or pulling really hard on a faucet handle when you turn it off is not going to stop a leak or a chronic drip. One of the most common things homeowners do is crank on it when it's not working. Pushing too hard can break the handle without solving the leak or drip problem.
6. Pouring grease down the kitchen drain
If you’re in the habit of pouring bacon grease down the kitchen-sink drain, you might as well try to stuff the whole pig down there. Grease is one of the best things for clogging drains. (So is all the soap we use in the bathroom, but that’s a harder habit to break.)
7: Using too much drain cleaner
When used judiciously and as directed on the right kind of clog, drain cleaners can be effective and relatively safe for drains. When used with abandon, they can corrode some drain materials, and they can actually make clogs worse. It’s also not very nice for the plumber who eventually comes out to clear that clog.
8: Screwing, nailing or cutting into a wall with hidden plumbing pipes.
Now we’re into the realm of “Oh, yeah. I did that once.” Do this with a screw and you might hear a fine spray of water hitting the back of the drywall. Do it with a reciprocating saw and you’re in for a gusher.