Measure the space you intend to dry

A 30-foot by 30-foot basement has 900 square feet of floor area. If a utility room stays behind a closed door, note that separately. One humidity reading beside the machine tells you little about the room on the other side. Take readings in the areas you want to use, and write down whether they were taken after rain or during an ordinary dry week.

Match the dampness to the capacity

ENERGY STAR groups spaces by dampness as well as size. For spaces under 2,000 square feet, its starting ranges are 20–30 pints per day for slightly to moderately damp conditions, 25–40 for very damp conditions and 30–50 for wet conditions. The rating describes moisture removal over 24 hours under test conditions. The bucket has its own, separate capacity.

900 ft² · occasionally musty

ENERGY STAR starting range: 20–30 pints/day.

900 ft² · persistently damp, damp spots

Starting range: 25–40 pints/day.

Water running down the wall

Trace the entry point as well as managing humidity.

Plan where the water will go

Picture emptying a filled bucket from the exact corner where the unit will sit. If that trip would be difficult, look at the model’s continuous drain option before buying. A gravity hose needs a route down to a suitable drain. If water must travel uphill, confirm whether the model has a pump and check its rated lift.

When the floor gets wet after rain

Mark where water first appears and when it happens. A puddle starting at the same wall after every storm deserves investigation even if the room air feels drier. Address the water entry as its own repair. Once the unit is running, check humidity in the far corner and confirm that the bucket or drain is collecting water.

For more detail, see ENERGY STAR’s capacity and drainage guide. Related reading: the sump-pump checklist before heavy rain.