A Homeowner’s Guide to Food Waste Disposals

Here at Nexus Plumbing, we know that for many Kiwis, the food waste disposal is a standard kitchen appliance we can’t imagine living without. It’s a feature that often impresses newcomers with its incredible convenience.

In this article, we’ll be using the common New Zealand terms ‘waste disposal’ or simply ‘disposal’.

A waste disposal allows you to deal with food scraps right at the sink, meaning you don’t have to keep a separate food waste bin in your kitchen. This eliminates problems like lingering odours, rubbish bags being torn open by cats or birds, and attracting pests like rats or cockroaches.

However, as convenient as they are, problems can arise from incorrect use. And while a waste disposal is an electrical appliance, because it’s so closely tied to your plumbing, it’s often a plumber you’ll call for installations and repairs.

How It Works

When you picture what’s happening inside a waste disposal, you probably imagine sharp blades chopping up the food. That’s a common misconception. Instead of blades, a disposal uses a spinning plate with small metal lugs (called an impeller). As it spins at high speed, food is thrown against the outside wall, which has a ridged surface like a cheese grater. This pulverises the food into particles that can be easily washed away with water.

Because there are no blades, there’s little risk of cutting your hand when cleaning—as long as you turn the power off first.

What You Should NEVER Put Down Your Waste Disposal

• ✘ Fibrous Foods: Celery, corn husks, and onion skins can wrap around the impeller and jam the motor.
• ✘ Starchy Foods: Pasta, rice, and potato peels expand with water and turn into paste, causing blockages.
• ✘ Coffee Grounds: These don’t wash away well and can accumulate in your drain.
• ✘ Fats, Grease, and Cheese: They solidify in the pipes and cause major blockages.
• ✘ Hard Materials: Bones, avocado pits, and eggshells can break the unit or jam the motor.

Always run cold water when using your disposal. After greasy foods, follow with hot water to flush the residue. In winter, grease solidifies faster—so be extra cautious.

Common Waste Disposal Problems & How to Fix Them

🔌 It Makes No Sound When You Turn It On

• Check the power source and test with another appliance.
• Try pressing the red or black reset button on the bottom.
• If that fails, the motor may be dead—time for a replacement.

🛑 It Hums for a Few Seconds, Then Stops

• TURN OFF THE POWER at the wall.
• Use a torch and pliers to remove any jammed debris.
• Try the manual rotation slot under the unit using an Allen key.
• Reset and test again. Repeat if needed or call a pro.

🚫 Motor Runs, But Water Won’t Drain

• This is likely a clog in the pipe—not the waste disposal itself.
• Use a plunger to attempt clearing.
• If frequent, a mechanical snake and drain cleaner is needed.

⚙️ It Makes a Loud Grinding Noise

• Foreign object inside—TURN OFF the power immediately.
• Remove using tongs. Be cautious of sharp edges.

💧 Water Leaking from Underneath

This typically requires a professional repair. Even small leaks can cause big damage if not properly sealed.

⚠️ Safety First

Always turn off the power at the wall before inspecting or attempting a fix. If you’re ever unsure, it’s best to call a licensed plumber.