What should you never put down the drain?

Fats, oils, and grease, often shortened to FOG, are the single biggest threat to your pipes. When you pour bacon drippings or pan grease down the drain, it goes in as a hot liquid. Inside the pipe it cools, hardens, and sticks to the walls. Layer after layer builds up until the opening narrows and waste can no longer pass. That is when the line backs up.

The numbers back this up. In its Report to Congress on sewer overflows, the EPA found that grease caused 47 percent of reported sewer blockages, more than tree roots, grit, or debris. The same report notes that "nearly three-quarters of SSO events in the arid Southwest were caused by blockages," which makes this a real concern for any Phoenix home tied to the city sewer.

The scale of the problem is large. The EPA estimates there are 23,000 to 75,000 sanitary sewer overflows in the United States every year, spilling 3 to 10 billion gallons of untreated wastewater. A lot of that starts at the kitchen sink, one grease pour at a time. Hot water and dish soap do not solve it. They only push the grease a little farther down the line before it cools and sets in a spot you cannot reach.

What to do instead is simple. Let grease cool in the pan, then scrape it into a can or an old jar and throw it in the trash. Wipe greasy pans with a paper towel before washing. A small jar by the stove costs nothing and keeps the worst clog-maker out of your pipes for good. This includes the fats you might not think of as grease, such as butter, lard, mayonnaise, salad dressing, sauces, and the fat skimmed off soups and stews.

Marketing calls them flushable, but the label is misleading. Wipes, paper towels, and feminine products do not break apart in water the way toilet paper does. They hold together, snag on rough spots in the pipe, and catch passing grease and debris until they form a dense plug.

Michigan State University Extension studied these products and put it plainly: "Flushable wipes do not break down like toilet paper and can cause clogs in your home's plumbing as well as the sewer system." The same goes for paper towels, which are built to stay strong when wet, and for cotton products, which swell and tangle.

The only two things that belong in a toilet are human waste and toilet paper. Toilet paper is designed to fall apart within seconds in water. Everything else, including wipes, dental floss, cotton swabs, and tissues, goes in the trash. Keep a small lidded bin in the bathroom so the trash can is the easy choice.

A garbage disposal grinds soft food scraps, but it is not a bottomless pit. Several common foods cause clogs in the drain line below the unit even when the disposal itself spins fine. InSinkErator, a leading disposal maker, advises that you "run cold water before, during, and after you operate your disposer" so scraps flush all the way through the pipe. Hot water melts fats that then re-harden downstream.

Here are the food items to keep out of the drain and disposal:

• Coffee grounds and eggshells. Grounds are fine and dense; they settle and pack together into a sludge at the bottom of the trap. Eggshells grind into gritty bits that join the same pile.
• Pasta, rice, and other starches. These keep absorbing water after they go down. They swell inside the pipe, turn into a gummy paste, and block the flow.
• Fibrous vegetables. Celery, corn husks, onion skins, and artichoke leaves have long, stringy fibers that wrap around the disposal blades and tangle in the trap.
• Fats, oils, and grease. Worth repeating here, since the kitchen sink is where most of it goes down.

For these, the trash or a compost bin is the right home. If your sink is already draining slowly after grinding food, that points to a clog in the line, not a jammed motor. See our page on why a garbage disposal is draining slow for how to tell the difference and clear it safely.

Some items do damage you cannot see right away. Harsh chemicals, paint, and solvents do not belong in any drain. Oil-based paint, paint thinner, motor oil, and similar products can corrode pipes, kill the helpful bacteria in a septic system, and pass through treatment plants into rivers and groundwater.

Liquid drain openers deserve their own warning. They work through a chemical reaction that gives off heat, which can soften plastic pipe and corrode older metal pipe over time. They also leave a tank of caustic water sitting in your sink if the clog does not clear, which is a burn hazard to you and to any plumber who opens the trap next. We cover this in detail on our page is Drano bad for pipes. A plunger, a hand snake, or an enzyme cleaner is a safer first move.

Medications are the last group to keep out. Flushing old pills sends drugs into the water supply, where treatment plants are not built to remove them. Most pharmacies and many police stations run free drug take-back programs. Use those instead of the toilet.

One more drain item worth a note is galvanized and older metal pipe. Pouring caustic openers and acidic products into aging pipe speeds up corrosion. The EPA warns that lead particles can attach to the inner surface of galvanized pipes and over time enter drinking water. Hard chemicals make that wear worse, which is another reason to skip them.

For all of these, the rules are the same three habits. Greasy and solid food waste goes in the trash or a grease jar. Paint, solvents, and chemicals go to a household hazardous waste drop-off, never the drain. Cans, glass, and other containers go in recycling once they are clean. These steps protect your home's pipes and the larger sewer system that every Phoenix property shares.

If a clog has already taken hold and a plunger does not fix it, or if you run a kitchen and your floor drains keep backing up, call a licensed plumber rather than reaching for chemicals. For restaurants and other food businesses, our guide on a commercial kitchen drain overflowing explains grease traps, the FOG rules, and how to keep a busy kitchen running. Catching a problem early is far cheaper than clearing a fully blocked main line.