Should I run hot or cold water with a garbage disposal?

The instructions that ship with disposals agree with each other, and they're specific.

• Waste King: "Run cold water during the disposal operation. This will keep waste and fats solid so the disposal can properly flush away the particles. It is not recommended to use hot water while running the disposal." Its steps start with a medium flow of cold water, before you switch the disposal on.
• Moen: its operating instructions for a batch feed model begin with "turn on a medium flow of cold water," then scrape in the food waste. Once the grinding stops, it says to run water for 15 seconds so all the waste is thoroughly flushed through the drain.
• InSinkErator: it says to run the disposal with a moderate flow of cold water, to keep the cold water running for a few seconds after grinding is complete, and to avoid hot water when grinding food waste. It adds that it is OK to drain hot water into the disposal between grinding periods.

So the rule is the same across brands: cold and moderate during grinding, and a short rinse afterward.

### How much water is enough?

A medium stream is the target. Waste King, Moen and InSinkErator all say a medium or moderate flow, so skip the trickle and skip the blast. Too little water is the bigger mistake. InSinkErator says an odor from the disposal "is usually a sign of food buildup, caused by insufficient water flow during and after use." In other words, the water is doing two jobs: it carries the ground food out of the unit, and it rinses the chamber so nothing sits and rots. If your disposal smells, our page on why a garbage disposal smells bad covers the cleanup.

Waste King's reason is the one to remember. Cold water "will keep waste and fats solid so the disposal can properly flush away the particles." Cold keeps fat firm, and firm bits are easier to grind and carry down the pipe.

Phoenix Water Services makes the flip side plain. If cooking grease or oil goes down a drain or toilet, "even when followed by hot water," the city says it "eventually cools down, congeals, builds up, and hardens," forming a plug in both the home and the city sewer lines. The city's point is that hot water does not change where the grease ends up. The city calls grease "the most frequent cause of sewer problems."

That is the honest answer to the old habit of running hot water to "melt" grease through the disposal. The habit doesn't help, and it can push the problem past your own trap into the line.

Run it longer than feels necessary.

• Before you switch it on: turn on the cold water first. InSinkErator's proper-use steps are to turn on cold water, turn on the disposal, and then gradually feed the food waste in.
• While it grinds: listen. InSinkErator says to feed food waste in gradually and to listen and wait for grinding to stop.
• After it stops: keep the water and the disposal running for about 15 seconds. Waste King says to let both run for approximately 15 seconds after shredding stops, so the waste is flushed through the trap and drain. Moen gives the same 15 seconds.
• Then shut off: turn off the disposal first, then the water. InSinkErator's last step is to turn off the disposal and then the water.

Two more habits help. InSinkErator says not to preload the disposal, which means you should not fill the chamber with food before you turn the unit on. And add scraps gradually rather than all at once.

### What if you use a batch feed disposal?

The rule is the same. Moen's batch feed instructions say to remove the stopper and turn on a medium flow of cold water, scrape in the food waste, insert the stopper to start the disposal, and lift the stopper to shut it off. Then run water for 15 seconds after grinding stops, so all the waste is flushed through the drain.

Hot and warm water aren't banned. They have a place, just not during grinding.

• Between grinding periods. InSinkErator says it is OK to drain hot water into the disposal between grinding periods, for example when you empty a pot of hot pasta water into the sink after the food is gone.
• When you clean the splash guard. Waste King says to turn the disposal off, scrub the underside of the splash guard with a scouring pad, baking soda and warm water, and then turn on warm water to rinse it. Nothing is being ground at that point. See how to keep a garbage disposal from smelling for the cleaning routine.
• When the sink is full of hot dish water. Let it drain, then run cold water and food through the disposal as usual.

The key point in each case is that food is not going through the unit while the water is hot.

Keep it out of the sink and the disposal entirely. InSinkErator says to never pour grease or fat into your garbage disposal or drain, and its food list carries the same warning on every disposal series. Phoenix Water Services gives a simple alternative: "Allow the grease or cooking oil to cool in the cookware that was used, and then scrape it into the trash can."

Phoenix also says a plugged sewer can bring "financial and regulatory" consequences for the city, and its campaign is called "Cease the Grease." For a home, the consequences are closer: a slow drain first, then a backup. If your kitchen sink is already slow, see why a garbage disposal drains slowly for what to check.

### What if you ran hot water down there already?

One time won't hurt. Run cold water for a minute to move things through, and keep the habit going forward. A pattern of hot water and greasy food is a different story, and it shows up as a slow drain or a smell coming from the sink. If that starts, the fix is cold water, less grease and a cleaning. When the sink keeps backing up, the clog is likely down the line, and a plumber can clear it with a cable or a jet.

### When should you call a plumber?

Call one if the sink drains slowly even when the disposal runs fine, if water backs up into the other side of a double sink, or if you smell sewer gas at the drain. Those point to the trap or the branch line, not to how you run the water. HQ is licensed and insured, offers 24/7 emergency service for backups, and gives free estimates and upfront pricing. If the disposal itself stops and won't restart, check where the reset button is first.

The water rules apply to every kind of scrap. For two foods people ask about most, see coffee grounds in a garbage disposal and eggshells, rice or pasta in a garbage disposal.

Water is one part of a bigger routine. See how to maintain a garbage disposal so it lasts and how to keep a garbage disposal clear of clogs.