Why Your Dishwasher Isn't Cleaning Dishes (It's Probably Not the Dishwasher)

I get calls about dishwashers not cleaning properly more than almost anything else. People assume the dishwasher is broken — maybe the pump is bad, maybe it needs a new motor, maybe it's just old. But here's the thing: I'd say 7 out of 10 dishwasher complaints I get are water temperature related. The dishwasher itself is fine. It's the water going into it that's the problem.

Before you spend money on a service call or start shopping for a new dishwasher, let me walk you through what's actually going on. Most of this you can check and fix yourself in about 15 minutes.

The #1 Reason: Your Water Isn't Hot Enough

Here's something most people don't realize: almost every modern dishwasher detergent — pods, tablets, powder — is enzyme-based. Those enzymes are what actually break down the food on your dishes. They're biological compounds that attack proteins, starches, and fats. But here's the catch: enzymes need a minimum water temperature of about 120°F to activate properly.

If your water heater is set to 110°F or lower (and a lot of them are, especially in homes with small kids where parents turn it down for safety), your dishwasher is running with water that literally can't activate the detergent. The soap is just sitting there doing almost nothing.

Most dishwashers have a built-in heating element that can boost water temperature a bit, but it's not designed to take 100°F water up to 120°F. It's there for a small bump — maybe 5-10 degrees. If the incoming water is too cold, the dishwasher simply can't compensate enough.

The Temperature Sweet Spot (and Why Too Hot Is Bad Too)

You might be thinking, "Okay, I'll just crank my water heater up to 150°F." Not so fast. Enzyme-based detergents have a sweet spot — roughly 120°F to 140°F. Below 120°F, enzymes don't activate. But above 140°F, you can actually kill the enzymes too quickly. They denature — basically cook — before they have time to do their job on the food residue.

For most households, setting your water heater to 120°F and using the dishwasher's built-in heating boost is the perfect balance. Your dishes get clean, your detergent works properly, and you're not wasting energy or risking scalding.

Stop Pre-Rinsing Your Dishes

This one blows people's minds, but you should NOT pre-rinse your dishes before loading them. I know — it feels wrong. Your parents probably rinsed everything. But modern enzyme detergents are designed to work differently than the old stuff.

Enzyme detergents need food residue to cling to. The enzymes literally look for proteins, starches, and grease to break down. If you've already rinsed everything perfectly clean, the enzymes have nothing to attach to and the detergent doesn't activate the way it should. Your dishes might actually come out worse because the detergent hasn't fully dissolved and rinsed away.

Scrape off the big chunks — bones, large food pieces, toothpicks — but leave the film and residue. That's what the dishwasher and detergent are designed to handle.

Your Detergent Might Be the Problem

Expired Detergent

Dishwasher detergent expires. Most people have no idea. Those enzyme compounds lose effectiveness over time, especially if the detergent gets exposed to moisture. If you bought a giant box of pods a year ago and they've been sitting under the sink in a humid kitchen, the enzymes may have already degraded significantly.

Pods and tablets need to stay dry until they're used. That film coating that dissolves in water? It's not a perfect moisture barrier. A humid cabinet is slowly killing your detergent. If your pods feel sticky, clumped together, or look discolored, they're past their prime.

Too Much or Too Little

More detergent doesn't mean cleaner dishes. In fact, too much detergent can leave a film on your dishes because it doesn't all rinse away. Follow the manufacturer's recommendation — for most pods, it's one pod per load. If you're using powder or gel, don't overfill the dispenser cup.

Clean the Filter (Yes, Your Dishwasher Has a Filter)

This is probably the most overlooked maintenance task in the entire kitchen. Most people don't even know their dishwasher has a filter, let alone that it needs to be cleaned regularly.

The filter is located at the bottom of the dishwasher tub, usually under the lower spray arm. It's a cylindrical mesh screen that catches food particles so they don't recirculate onto your clean dishes. If it's clogged — and after months or years of never being cleaned, it almost certainly is — dirty water is just spraying back onto your dishes every cycle.

Pull it out (most twist-lock out), rinse it under running water, and use an old toothbrush to scrub off the buildup. Do this once a month. You'll be amazed at the difference.

Check Your Spray Arms for Clogs

The spray arms are those rotating arms that shoot water around the inside of the dishwasher. Each arm has a series of small holes that create the water jets. Over time, those holes get clogged with mineral deposits (especially here in Utah where we have hard water), food particles, or bits of labels from jars.

Pull out both spray arms — the one under the lower rack and the one under the upper rack. Hold them up to the light and look through each hole. If any are blocked, use a toothpick or a thin piece of wire to clear them out. Rinse the arms under running water and shake out any debris trapped inside.

Quick Checklist Before You Call for Repair

Run through this list before spending money on a service call. Most dishwasher cleaning complaints are solved by one or more of these:

• Check your water heater temperature. It should be set to at least 120°F.
• Run hot water at the kitchen sink for 30-60 seconds before starting the dishwasher.
• Stop pre-rinsing dishes. Scrape off big pieces, leave the rest.
• Check your detergent. Make sure it's not expired, sticky, or clumped.
• Clean the dishwasher filter. It's at the bottom of the tub — twist it out and scrub it.
• Clear the spray arm holes. Use a toothpick to poke out any clogs.
• Run a hot cleaning cycle once a month — empty dishwasher, hottest setting, no detergent, a cup of white vinegar on the top rack.

When It Actually IS the Dishwasher

If you've gone through everything above and your dishes still aren't getting clean, then we're looking at an actual mechanical problem. The wash motor could be failing (you'd usually hear a difference in sound), the water inlet valve might not be letting enough water in, or the heating element could be burned out so the dishwasher can't boost the water temperature at all.

At that point, it's worth having a tech take a look. We do dishwasher repair across the Salt Lake area and can usually diagnose the issue in the first visit. But honestly, try the simple stuff first — there's a really good chance that's all you need.