It scales faster than a kettle because it never holds a potful of water
A kettle boils a litre at a time: the minerals in that litre come out of solution once and settle on the element. A garment steamer works differently — a pump pushes a few millilitres of water into a small metal block held around 140 to 180 °C, the water flashes to steam almost instantly, and another few millilitres follow. The same water is repeatedly being boiled dry in a tiny chamber, so every millilitre leaves its minerals behind on the same few square centimetres. Given the same water, a steamer fouls several times faster than a kettle.
And that makes the choice of water the whole story. Tap water carries roughly 100 to 300 mg of calcium carbonate per litre. Bottled mineral water is often 200 to 500, because "mineral" is literally what it says on the label — it is water with minerals added or preserved. So the bottle people buy because it seems cleaner and safer is the one that destroys the machine fastest. Distilled or deionised water carries almost nothing, and that is what these appliances are designed to drink.
The scale does two things. It narrows the channel until not enough water gets through to make steam, and because scale is a poor conductor of heat, it insulates the metal from the water — the block then overheats and the thermal cut-out trips. That is the "works for two minutes then stops" pattern people mistake for a broken thermostat. It is a coating of chalk inside a sealed block.
Three faults, three answers
Pump noise but no steam is the scale case, and it is repairable if the tank comes off. Twenty grams of citric acid in 500 ml of warm water, into the tank, then hold the steam button in short bursts — five seconds on, ten seconds off — for twenty to thirty minutes, so the solution sits in the block long enough to work. Empty it, run two tanks of clean water through, and try again. Citric acid rather than vinegar or a strong descaler: the block is usually aluminium, and strong acid attacks both the metal and the seals.
Nothing at all — no lamp, no sound is electrical, not scale. Test the socket, look at the indicator, check the manual for a reset, and only then consider the thermal fuse, which is a solder link inside and usually means opening the machine. On a cheap steamer that is rarely worth it.
Sputtering with water droplets is usually the simplest thing on the page: a low tank, so the pump is drawing air between slugs of water. Fill it, then check the head — the steam holes block with the same scale and can be unscrewed and soaked. If it still spits with a full tank, the one-way valve in the tank fitting is letting air back in, which on most models is a part rather than a repair.