How we made this guide: picks, prices and specs come from our catalog and the makers' published specs, owner quotes come from customer reviews on our product pages and the guide was drafted with AI help, then checked and edited by Trevor Hall.
To install a crawl space dehumidifier, seal the space first, set the unit level where air can circulate around it, run the condensate hose to a drain, sump or outside, plug into a GFCI outlet, set the humidistat and check the humidity after a few days. A machine with a built-in pump, such as the XPOWER Viking BD-65 at $879, makes the drain step the easiest.
Plan on an afternoon for one unit. Difficulty is low to moderate: no refrigerant work, but a tight space, a hose run and possibly an electrician for the outlet.
Quick answer
Seal, place, drain, power, set, check. That is the whole job. The order matters: a dehumidifier in an open, vented crawl space is working against outside air, and a drain hose that slopes the wrong way floods the unit. Compare machines in our crawl space dehumidifiers or browse all dehumidifiers.
Tools and equipment you need
Most of the kit is already in a contractor's truck. For a single unit you need:
- A dehumidifier rated for the space, with its drain hose and clamp.
- A level, plus blocks or a pad to stand the unit on.
- A GFCI-protected outlet within cord reach. If there is none, an electrician adds one.
- Extra hose or a separate pump if the drain point is far away or higher than the machine.
- A bucket to test the drain and a separate humidity meter.
Four machines we carry show the main choices, with install details from each manual.
Built-in pump
XPOWER VIKING Commercial Grade Dehumidifier for Crawlspace, Basement, Attic, Garage BD-65
$879
Gravity drain or a built-in pump, so it suits a crawl space where the water has to travel.
Step 1: Seal the crawl space first
The XPOWER manual says to run the unit in an enclosed area and keep doors, windows and other outside entrances closed. In a crawl space that means closing the access door, covering exposed soil with a vapor barrier and dealing with foundation vents in line with your local code.
Closing the vents makes it an unvented crawl space under the International Residential Code (section R408.3), which calls for a sealed ground cover plus a way to treat the air: an exhaust fan, conditioned supply air or, in current editions, a dehumidifier. Sizing rules depend on the edition and local amendments, so ask your building department before you close anything.
Our guide to venting a crawl space covers open, closed and sealed setups. If mold is already present, remediation comes first; see crawl space mold remediation.
Step 2: Choose the spot and set the unit level
Pick a spot near the access point, close to power and close to the drain. Leave the air inlet and outlet uncovered. The RM40-SH manual asks for 0.5 m (about 20 in) of clearance from any surface at the inlet and outlet, and the BD-65 manual sets a 10 cm (about 4 in) minimum from adjacent structures. The BD-65 manual also says not to use it where gasoline, paint or other flammable goods are used or stored, so clear stored paint and fuel out of the crawl space first.
The CD85's manual shows its grille and blanking covers can be swapped to change the airflow direction, which helps when the unit has to sit against a footing.
Level matters for two reasons. Condensate that cannot reach the outlet backs up inside the machine, and the BD-65's pump logic needs the unit level: its manual lists an E4 error when the machine is not positioned level. Set the unit on blocks or a pad to keep it off damp soil, and check it with the level in both directions.
Do not run the machine the moment it comes out of the truck. The XPOWER manual says to stand the unit upright for at least 1 hour before use so the refrigerant stabilizes, and for at least 4 hours if it traveled on its side or upside down.
Floor or hanging
Three of the four are floor units. The BD-65, CS60 and CD85 manuals describe use on a level surface and none describes hanging, so stand them on a pad or blocks, not from joists. The RM40-SH is the exception. Ebac's spec sheet lists it as free standing with a wall mounting bracket as an option, and our product page lists the bracket with it. The manual's package list shows no bracket, so confirm it before you plan a wall mount (contact us). On a wall, keep the drain outlet above the drain point so the hose still runs downhill.
Step 3: Run the drain
This is the step that decides whether the job works for months without attention. You have two options.
- Gravity drain. The hose runs downhill to a floor drain, a sump pit or outside. The Ebac CS60 manual lists a blocked or frozen drain pipe, a drain pipe that is too high and crimped tubing as the causes of water flooding inside the machine, and says no section of the drain hose may sit above the level of the water outlet.
- Pump drain. A pump pushes the water uphill or a long way. The XPOWER manual says not to lift the drain hose higher than 16 ft above the machine. Ebac's CD85 manual is stricter: no section of its hose should sit more than 1 m (about 3 ft) above the water outlet. For a higher lift, use the BD-65's pump or add an external condensate pump.
Whichever you choose, check local rules for where the water may go. Confirm the sump, storm drain or outdoor release is allowed in your area.
Fitting the hose
On the XPOWER, unscrew the nut at the drain hose connection, pass the hose through the nut, insert the hose and screw the nut back on. Put a separate container at the far end to collect the water, and test the run with a bucket before you leave.
The CS60 and RM40-SH manuals list a 3 m (about 10 ft) PVC tube with a 12 mm inside diameter and one hose clamp. For a longer run you need to add tubing or a pump.
| Machine | Price | Drain | Hose | Weight |
|---|---|---|---|---|
| XPOWER Viking BD-65 | $879 | Gravity or built-in pump | 20 ft, pump lift up to 16 ft | 55.1 lb |
| Ebac CD85 | $2,600 | Internal condensate pump, hose no more than 1 m (about 3 ft) above the outlet per manual | 25 ft per Ebac's spec sheet | 75 lb |
| Ebac CS60 | $1,800 | Gravity, no internal pump | 10 ft | 63 lb |
| Ebac RM40-SH | $1,300 | Gravity, no internal pump | 10 ft (3 m) | 50 lb |
Gravity drain
Ebac CS60 Commercial Crawl Space Dehumidifier 10264CS-US
$1,800
No internal pump, so plan a downhill hose run or add an external pump.
Step 4: Power it safely
Use a GFCI outlet. The XPOWER manual says to use the unit only with GFCI-protected receptacles and to contact a qualified electrician to verify or install one if necessary. In homes, the National Electrical Code requires GFCI protection for 125-volt, 15 and 20 amp receptacles in crawl spaces at or below grade (NEC 210.8(A)); your local edition and inspector have the final word. Keep the cord off wet ground and away from foot traffic; the XPOWER manual says not to operate the unit near pooled water.
The Ebac manuals call for a grounded 15 amp outlet. The CS60 and CD85 are listed on our pages at 7 A maximum, 880 W maximum; the XPOWER BD-65 is listed at 520 W, and its manual gives 4.2 A. Ebac's RM40-SH spec sheet lists 3.3 A and 344 W. Ask an electrician whether a machine needs its own circuit when the crawl space has other loads.
Step 5: Set the humidistat
On the XPOWER BD-65 you tap the plus and minus buttons to change the target humidity in 1 percent steps, across a range of 36 percent to 90 percent. The default setting is 36 percent. The unit then needs about 3 minutes to start up, and the manual says that after a power loss it returns to its last settings when it is switched back on, so check it after an outage.
The Ebac CS60, CD85 and RM40-SH use a humidistat knob. The CS60 manual says to turn the knob until the unit turns on, and the RM40-SH manual describes turning it clockwise to the maximum setting for the first test run.
The EPA advises keeping indoor relative humidity below 60 percent, ideally 30 to 50 percent. Set the crawl space unit to a target under 60 percent, then confirm it with your own humidity meter. The BD-65 ships set to 36 percent, the bottom of its range, so raise it to your target or it will keep running until the space reaches 36 percent. To size the machine, see what size dehumidifier do I need.
Internal pump
Ebac CD85 Industrial Dehumidifier 10293GR-US
$2,600
Internal condensate pump for short lifts: Ebac's manual keeps the hose within 1 m (about 3 ft) above the water outlet.
Step 6: Test the first run
Ebac gives a short test for correct operation. Place the unit on a level surface, start it and confirm the compressor is running. Leave it for 15 minutes, then look at the evaporator coil. The CS60 manual says that below 80°F an even coating of frost should cover the coil, and above 80°F frost or droplets of water should. After about 55 minutes of continuous running the unit enters hot gas defrost for 5 minutes and returns to normal on its own. The RM40-SH manual uses 70°F as the frost threshold instead, and its defrost is temperature-sensitive, about once an hour below 59°F.
If you switch a CS60 or CD85 off, wait at least five minutes before restarting it. The RM40-SH manual says at least three. Wait the longer time.
Compact
Ebac RM40-SH Crawl Space Dehumidifier 10187SH-US
$1,300
The lightest of the four at 50 lb, and the only one with a wall bracket option, for a small or tight crawl space.
Step 7: Check the humidity after a few days
A dehumidifier takes time to bring a space down. Do not judge it in an hour. Read a humidity meter on day one, after three days and again after a week. If the number is not moving, look for outside air, a wet floor with no vapor barrier or a stopped hose. For run hours and cost, see how much it costs to run a dehumidifier.
| Check | When | What you want to see |
|---|---|---|
| Space sealed | Before install | Access door closed, ground covered, vents handled per local code |
| Unit level | At install | Level in both directions, off damp soil |
| Drain test | At install | Water reaches the sump, drain or outside with no low spots or kinks |
| GFCI outlet | At install | Outlet is GFCI protected and the cord is clear of water and foot traffic |
| Coil check | 15 minutes in | Compressor running, frost or water droplets on the coil |
| Humidity reading | Day 1, day 3 and day 7 | Falling toward your target on a separate meter |
| Hose and filter | Monthly at first | Hose flowing, filter clear; see dehumidifier maintenance |
Large or divided crawl spaces
Our listings give suggested areas of 800 sq ft for the RM40-SH, 1,000 sq ft for the CD85, 1,300 sq ft for the BD-65 and 1,500 sq ft for the CS60. The BD-65 manual notes that larger enclosed areas may need more than one dehumidifier and suggests keeping air moving, for example with an air mover.
Where ducting fits
Of the four, only the XPOWER BD-65 takes a duct: its manual shows an optional intake duct, over 6.5 in diameter, on the intake adapter, while exhaust ducting is for the BD-90 and BD-120 series only. If your crawl space is long or divided into sections, a fully ductable dehumidifier lets you move dry air to the far end. Follow the maker's manual for duct size and length. See our ductable dehumidifiers and the crawl space venting guide, which features the ductable BD-90P.
Common mistakes
- Installing in an open, vented space and expecting the humidity to drop.
- Leaving the unit tilted or sitting on wet soil.
- Running the hose uphill on a gravity drain, or pulling a pump hose above the maker's lift limit.
- Skipping the GFCI outlet, or using an extension cord instead of an outlet within the unit's cord reach.
- Judging the result after one hour instead of a few days.
- Never checking the drain again after the first week.
If you are comparing machines before you buy, our best crawl space dehumidifier guide ranks them, and how a dehumidifier works explains refrigerant, LGR and desiccant models. For a damp basement, see basement mold remediation. For encapsulation, read our crawl space encapsulation guide.
Frequently asked questions
What setting should a crawl space dehumidifier be on?
Set it below 60 percent relative humidity, the ceiling the EPA gives for indoor air (it suggests 30 to 50 percent where possible). The XPOWER BD-65 accepts 36 percent to 90 percent in 1 percent steps; on the Ebac knob units, turn the knob until the unit runs. Then read a separate humidity meter for a few days and adjust.
Do all crawl spaces need a dehumidifier?
No. It depends on the measured humidity and on whether the space is sealed. Measure first with a meter over several days. If the readings stay high after the space is sealed, a dehumidifier is the next step.
Is it worth putting a dehumidifier in a crawl space?
It is worth it when a sealed crawl space still reads above 60 percent relative humidity on a meter over several days. If the space is vented and open, seal it first, because the machine would be drying outside air. If readings already stay below 60 percent, you may not need one.
How long should I run a dehumidifier in a crawl space?
Most units cycle on a humidistat, so they run until the set humidity is reached and then rest. Run time depends on the space, the weather and the machine.
Can I use a dehumidifier in a crawl space without encapsulation?
You can, but it works against outside air. The XPOWER manual calls for an enclosed area with outside entrances closed. Sealing the space first gives the unit a smaller job to do.
What can I put in a crawl space to absorb moisture?
A vapor barrier over bare soil limits moisture from the ground, and a dehumidifier removes water from the air. For standing water, fix the source first.
Can a dehumidifier drain without a pump?
Yes. The CS60 and RM40-SH have no internal pump and rely on gravity, and the BD-65 offers a gravity drain as well as a built-in pump. The hose must run downhill, with no section above the water outlet on the CS60.
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