The reason your dishwasher tablet isn’t dissolving properly – and the placement trick engineers recommend

Most people discover their dishwasher has a “tablet problem” the same way: you open the door after a full programme, plates are still grimy, and there’s a chalky lump sitting in the dispenser or rolling around on the filter. You run the machine again, maybe change brand, maybe switch to pods. The next week, the same half‑melted tablet is glued to the inside of the door like a tiny, expensive fossil.

Ask a dishwasher engineer about it and they rarely blame the tablet first. They talk about water, angles and timing. In their world, a tablet that doesn’t dissolve properly is usually a symptom of where it sits and how the machine is loaded around it, not a mystery flaw in the detergent itself.

One trick comes up again and again in service visits and training manuals: where you place the tablet matters more than most households realise. And in certain machines and programmes, there’s a small placement tweak that makes the difference between a cloudy glass and a genuinely clean one.

Why your tablet is coming out half‑melted

Dishwasher tablets are designed to dissolve under three conditions: enough water, enough heat and enough movement. If any of those are off, you get the tell‑tale sludge left behind.

In real kitchens, that usually looks like one of these:

• The tablet is still sitting in a damp lump in the dispenser.
• It has fallen onto the floor of the machine and stuck near the filter.
• It is partly smeared along the inside of the door like wet chalk.

Behind that mess are a few quiet culprits.

Engineers will tell you: if water can’t hit the tablet properly, it can’t use the tablet properly.

The usual suspects

Three design details do most of the damage:

1. Blocked or weak spray arms
   If food, limescale or a stray seed clogs the little jets, the water fan gets patchy. The stream that should blast across the door and dispenser never arrives, so the tablet softens, then sits.

2. The “wall” of plates and trays
   When big dishes lean in front of the dispenser flap, they act like a shield. The door pops open mid‑cycle, but all the tablet meets is the back of a roasting tin. The water swirls behind it, not over it.

3. Cool, eco and short programmes
   Modern machines save energy by using cooler water and pulsing the spray. Brilliant for the bill, slightly fussier for solid detergent. If the hot phase is short or the tablet only gets a few weak bursts of water, the core often survives the wash.

Hard water and old tablets add a final twist. In very hard‑water areas, the outer layer of some tablets dissolves more slowly. If they’ve sat in a damp cupboard and picked up moisture, they can also clump and stick inside the dispenser before the cycle even starts.

The placement trick dishwasher engineers actually use

On a lot of call‑outs, once basic faults are ruled out, engineers do something that surprises people: they stop using the little detergent flap for certain programmes.

Instead, they place the tablet directly in the path of the strongest spray, usually:

• Flat in the cutlery basket, or
• On the floor of the machine, towards the back, directly under the lower spray arm, away from the filter.

The logic is boringly practical. Those spots get hit by high‑pressure water from the start of the main wash. There is no door to open, no stack of plates to block it, no lip for the softened tablet to wedge under.

“If in doubt, put the tablet where the water works hardest, not where the plastic door looks neat,” as one engineer put it during a training session.

When this trick helps most

This placement tweak tends to make a visible difference when:

• You mostly run eco or quick programmes.
• You have large plates or trays that sit right in front of the dispenser.
• The inside of the dispenser looks pitted or sticky, so tablets catch on the way out.
• The tablet routinely falls out as a lump when you open the door mid‑cycle to check.

Manufacturers officially prefer you to use the dispenser, and for full‑length, hotter programmes in modern machines that usually works well. But many engineers quietly admit they load tablets in the cutlery basket at home on eco cycles because it simply dissolves more reliably.

If you try this, always check your manual first. A few machines with built‑in pre‑wash systems or very fine filters will specify where loose detergent should (and should not) go.

How to try the placement tweak tonight

You don’t need tools; you just need one wash where you’re willing to pay attention instead of pressing “start” and forgetting.

1. Do a quick health check
   Spin the spray arms by hand. They should turn freely and not catch on tall items. Use a cocktail stick or toothpick to gently clear any blocked jets. Check that the dispenser door opens and closes smoothly.

2. Choose the right programme
   Pick your usual eco or normal wash, not the very shortest 30‑minute rinse. The placement trick amplifies water contact; it doesn’t turn a rinse into a full wash.

3. Place the tablet deliberately

   • Option A: Put the tablet flat in the cutlery basket, ideally under a gap where the upper spray arm can hit it.
     
   • Option B: Lay it on the base of the machine, at the back, just off the filter cover, directly below the lower spray arm. Make sure it cannot slip into the filter.

4. Load around the water, not around the tablet
   Avoid leaning a baking tray or chopping board flat against the lower spray arm. Keep big plates a few centimetres clear of where the main jet needs to travel.

5. Check the result once
   When the programme finishes, look for any tablet residue on the base or basket. If it has vanished and dishes look cleaner, you’ve found your machine’s sweet spot.

The aim is not to rebel against the dispenser forever. It’s to learn how your particular machine throws water and to place detergent where that pattern actually reaches.

Everyday loading habits that quietly sabotage tablets

Most tablet dramas come down to a few repeat habits that no one thinks about at 7 p.m. on a Tuesday.

• Blocking the dispenser door
  A single oversized plate, chopping board or pizza tray pressed against the inner door can physically stop the flap opening, or trap the tablet when it falls.

• Overfilling the cutlery area
  When the basket is jammed with spoons and knives, a tablet tucked among them can get “caged in”, softening but never flushing out properly.

• Laying plastics over the base
  Lightweight plastic tubs or lids on the bottom rack can blow around in the wash, land on a dissolving tablet and shelter it from the spray.

• Mixing powder and tablets
  Adding loose powder “for luck” when using a tablet can create a gluey paste that sticks to the dispenser and slows everything down.

A small mindset shift helps here: load for clear water paths, not just for maximum capacity. If you can “see” an invisible fan of water spraying from each arm without hitting a wall of crockery, your tablet already has a better chance.

Quick reference: common problems and simple tweaks

Problem you see after a wash	Likely cause	Simple change to try
Tablet still in dispenser, edges soggy	Blocked spray, dispenser shielded by plates	Clear jets, leave a gap in front of dispenser or use cutlery‑basket placement
Tablet in a lump on the filter	Fell out too early, stuck in cooler water	Place at back, under spray arm, or switch to a slightly hotter/longer programme
Cloudy glasses and film on plates	Tablet only partially dissolved; hard water	Placement trick plus rinse aid and salt set to local hardness

A small maintenance ritual that makes everything easier

Once a month, engineers suggest a ten‑minute reset:

• Run the hottest, longest programme empty with a dishwasher cleaner or a bowl of white vinegar on the top rack.
• Pop off the spray arms (if your model allows) and rinse them under the tap; clear any grit from the jets.
• Remove the filter, rinse it, and clear the sump of broken glass, bones or fruit pips.

Think of it as dusting the “plumbing” your tablet relies on. A clean, free‑spinning spray system turns nearly any decent tablet into a good clean, regardless of brand.

A realistic plan for consistently dissolving tablets

You do not need to memorise the fluid dynamics of your dishwasher. A few simple moves, repeated, are enough.

• Keep big trays away from the dispenser and the main spray path.
• On eco or short cycles, try the tablet in the cutlery basket or under the lower spray arm.
• Clear spray‑arm jets and rinse the filter every few weeks.
• Store tablets somewhere dry; close the tub or bag so they don’t pick up moisture.

The unglamorous truth is that most tablet problems are not about magic formulas. They’re about water being able to reach what you’ve already paid for. Place the tablet where the machine actually works hardest, and suddenly the expensive “multi‑action” square does the simple thing you wanted all along: it disappears.

FAQ:

• Is it safe to put the tablet in the cutlery basket? In most machines, yes, as long as it cannot fall into the filter and metal items cannot wedge it in place. Many engineers use this trick themselves for eco cycles. Always check your manual, as a few models specify dispenser use only.
• Should I remove the plastic film from my tablet? If the wrapper is labelled “water‑soluble” you can leave it on. If not, you must remove it or it will act like a raincoat and stop the tablet dissolving properly.
• Can I break tablets in half for smaller loads? You can, but they may crumble and dissolve unevenly. If you regularly run small loads or very short programmes, a dedicated “compact” tablet or powder in the main wash compartment is usually more reliable.
• Does switching brand fix dissolving problems? Sometimes the coating thickness and composition differ, but if placement and water flow are wrong, even premium tablets will struggle. It’s worth fixing spray, loading and programme choice before spending more on detergent.
• My machine is old – does the placement trick still help? Often it helps more, because older dispensers can stick and older spray arms are easier to block. As long as the pump and heater still work, placing the tablet in the main spray path can buy you a lot more life from the appliance.