There is water on the floor

Six causes, in order

1. 1The bucket is not seated. A tank pushed in at an angle, or with a displaced float, lets water past the seal. Remove it fully and refit it squarely - this takes ten seconds and is a genuinely common cause.
2. 2The drain hose has a sag or a blockage. Water pools in the low spot, the pool blocks the line, condensate backs up into the tray and over. Run your hand along the whole route; any section not falling continuously is the fault. Coiled excess hose behind the machine is the classic version. Drain not working.
3. 3The unit is not level. A machine tilted away from its drain port pools water in the tray until it spills. Check with a level; the feet are often adjustable.
4. 4A hose fitting is weeping. Usually a missing or perished hose washer, or a plastic port cracked by over-tightening. Hand tight with a washer is correct; a wrench is how the port cracks. Hose fittings.
5. 5The pump has stopped, on a pump model. Most designs shut the unit down when the reservoir float trips, but some will keep producing condensate. If the pump is silent while the machine runs, that is the cause. Pump lift and distance.
6. 6The condensate tray is cracked. Rare, and the diagnosis of exclusion: a steady leak with no blockage, a level machine, a seated bucket and sound fittings. It is a warranty claim rather than a repair, because the tray sits under the coil assembly.

Two things that look like leaks and are not

• Condensation on the outside of the casing. In a very humid room, a cold surface will sweat. It is uncommon on a dehumidifier casing because the exhaust air is warm, but it happens and it is harmless.
• Water at the far end of the drain hose, not at the machine. That is the drain working. Check where the water actually starts before deciding the machine is at fault.

The pump-failure question worth asking before you buy

There are two ways a pump model can fail and manufacturers do not advertise which one applies. The good failure: the pump stops, the reservoir float trips, the machine shuts down, and you find a dry unit that has done nothing for a week. The bad one: the pump stops and the tray overflows.

You cannot control which design you get, but you can control the fallback. A pump model with a large bucket - the GE at 1.8 gallons, the Frigidaire pump model at 1.7 - can hold roughly seven hours of condensate if the pump quits. That turns a wet floor into a full bucket, and it is the most useful thing a large tank does on a pump machine. Capacity versus tank size.

Preventing the repeat

• Cut the hose to length instead of coiling the excess, and support the run along a wall rather than letting it lie loose on the floor.
• Flush the drain line once a season. Two minutes with a tap clears biofilm before it becomes a plug.
• Put the machine on a level surface, and check it after anyone moves it.
• Site it where a small spill is survivable - on concrete rather than on carpet, and not directly above a finished ceiling.
• Check the hose route a week after setting it up. Most drainage faults appear over days as the hose settles, not in the first hour.