Step-by-Step Guide: Using a Dehumidifier After Flood Damage
Cleaning up after flood damage can be overwhelming. Water penetrates floors, walls, and furniture quickly. Then, even when the water recedes, moisture remains. That excess moisture creates the real problems. Mold can appear within 24 to 48 hours of flooding. You can prevent mold by using a dehumidifier effectively.
Follow this step-by-step guide to learn how to use a dehumidifier after flooding, from hour one all the way until the job is complete.
Step 1: Assess for Safety Before Entering
Safety first. Before you enter your home with any equipment, make sure it’s safe. Check for structural damage like sagging ceilings, bowed walls, or water around electrical outlets. Shut off power at the breaker box if there’s any chance of water coming in contact with electricity. Water and electricity don’t mix.
Put on rubber boots, rubber gloves, and a protective face mask. Floodwater contains bacteria, sewage, and chemicals you don’t want to breathe or touch. If you’re protected, you can work longer and stay safe while restoring your home.
Step 2: Document Damage with Photos and Videos
Capture video and take photos of the affected areas before you do anything else. Walk through each room and photograph walls, floors, ceilings, and damaged property. Your insurance company will need this info to process your claim. Take as many detailed pictures/videos as you can.
Upload the files to your cloud storage account or email them to yourself right away. You don’t want to lose that valuable documentation.
Step 3: Remove Excess Water Before Starting
You cannot use a dehumidifier instead of water extraction. The machine only extracts water from the air. If there is standing water on the floor, remove it first.
Use wet/dry vacuums, pumps, or mops to get rid of excess water. Remove as much water as you can before switching on the dehumidifier. A wet room slows down the drying process significantly.
Remove any carpets, rugs, or wet upholstered furniture you can. These items absorb water and will only prolong drying time. It’s usually easier to dispose of saturated carpets than try drying them in place.
Step 4: Select the Correct Dehumidifier for the Job
Dehumidifiers range from small room units to massive commercial models. Do not try to use a small unit meant for bedrooms in a flooded basement or family room.
For larger water-damaged areas, use a refrigerant-style dehumidifier. These units excel at warmer temperatures and higher humidity levels which you’ll likely find with flood damage. If the room is cool, use a desiccant model instead.
Desiccant dehumidifiers are more efficient at pulling moisture from the air in cool temperatures.
Rent a commercial-grade dehumidifier if the flooding was severe. Commercial models extract hundreds of pints of moisture every day. Professional restoration teams use machines that remove over 100 pints of water per day.
Step 5: Place the Dehumidifier Properly
Placement is important. Place the unit in the middle of the room when possible. This allows for air to be pulled from all directions. Leave 1-2 feet of clearance around the entire unit so air can freely flow in.
Don’t place it in corners or up against walls. Obstructed airflow diminishes moisture output.
Work on the worst room first if multiple rooms are flooded. Once the space reaches safe humidity levels, move the unit to dry other areas.
Step 6: Adjust Humidity Settings
Turn on the dehumidifier and set your desired humidity level between 30-50%. With flood damage, you’ll want to get the humidity as low as possible. Set the dial to the minimum setting your unit allows, preferably 30%.
Dry climates average 30-50% humidity on a daily basis. After flooding, that number jumps to 80% or higher. Setting the unit to a low target forces it to work harder and dry the area more quickly.
Step 7: Use Fans To Circulate Air
Box fans and high velocity fans help air circulate around the room. Set up fans in the room with the dehumidifier to move air. Face the fans toward wet surfaces and across the dehumidifier’s air intake.
Place one fan to blow air across the wet wall/floor. Position another fan so that air blows towards the dehumidifier. This creates a cycle of moving air that speeds evaporation and allows the unit to collect more moisture each hour.
Do not open windows unless the air outside is dryer than the air inside. If it’s humid outside, keeping windows open will only introduce more moisture.
Step 8: Empty the Water Bucket
If you’re using a standard home dehumidifier, there should be a small collection tank inside. After a flood, you’ll likely need to empty this bucket every few hours. When the tank reaches maximum fill, your unit will shut off. An empty unit will slow down the drying process.
If your unit has a drain port, attach a hose and place the other end in a bucket. Some models come with hoses, while others require you to purchase one separately. This allows you to continuously run the dehumidifier without stopping.
Step 9: Monitor Humidity Levels Over Time
Purchase a hygrometer to monitor humidity levels throughout the day. Hygrometers are affordable and available at local hardware stores. You can track the room’s humidity percentage as the dehumidifier runs.
The goal is to bring the humidity down below 50% relative humidity.
Consider purchasing a moisture meter to keep track of hidden moisture. Moisture meters detect how much moisture is inside the walls, floors, and wood surfaces. You can’t always see water with the naked eye. A moisture meter will tell you if water is still present even after surfaces dry.
Step 10: Continue until the Humidity Stays Low
Leave the dehumidifier running for at least one to three full days. Some severe floods can take up to a week to fully dry, depending on how much water was involved. Check your moisture meter readings each day.
When all readings return to normal and stay below 50% humidity, you can safely turn off the unit.
Case Study: Basement Flooding from Heavy Rainfall
Client: Residential customer with flooded basement (120 m²)
Problem: Outside rain water entered the basement through cracks, causing some standing water, soaked carpets, and overall humidity above 85%. Odor developed after 36 hours, and slight mold was beginning to show on lower walls.
Solution Details:
Immediately pumped out standing water with a wet/dry vacuum. Removed carpets and furniture that absorbed too much water.
Used a commercial refrigerant dehumidifier rated for over 100 pints per day.
Put the dehumidifier in the center of the room and let it breathe (1–2 feet from walls/furniture).
Set humidity levels to 30% for faster drying.
Added several high-velocity fans for air circulation across damp areas, blowing towards the dehumidifier.
Monitored using a hygrometer and moisture meter to measure both air AND wall/metal humidity.
Attached a drain hose so the customer could leave it on without having to empty the bucket.
Case study - https://www.sedgwick.com/blog/tackling-the-challenges-of-basement-flooding/
Results:
Humidity was lowered to below 50% within 48 hours.
The entire structure was dry in 5 days.
Prevented further mold development.
Saved customers from expensive repairs/remediation.
Moral of the story: Don’t wait too long. Act quickly. Use the right tools and monitor the job until complete. Using a dehumidifier with complementary air circulation will cut your drying time significantly.
FAQs:
1. How quickly should I start drying with a dehumidifier?
As soon as the bulk of standing water is gone. Mold can grow within 24–48 hours so time is of the essence.
2. Will a dehumidifier pull up standing water?
No, you need to get rid of the standing water first. Use a pump, wet/dry vacuum, or large sponge/mop to soak it up before using a dehumidifier.
3. What kind of dehumidifier do I need to dry out flood damage?
If your main concern is indoor humidity after a flood, we recommend…
Refrigerant dehumidifiers for warmer/climate conditions
Desiccant dehumidifiers for cooler environments
…and if the flooding is severe, go with a commercial-grade unit.
4. What humidity level should I set for flooding?
30% to begin with because you want the drying process to happen quickly. Afterwards, keep humidity below 50%.
5. How long do I need to run my dehumidifier after flooding?
This can vary anywhere from 1 day to over a week depending on severity. Until your readings start showing <50% on your hygrometer, you should keep it running.
6. Should I be using fans with my dehumidifier?
Yes! Fans allow for better air circulation and force moisture to evaporate quicker (making it easier for your dehumidifier to do its job).
7. Where is the best place to put my dehumidifier?
We recommend placing your dehumidifier…
In the center of the room with access to all walls
At least 1–2 feet away from walls/furniture
…Start with the room that was most affected and move from there.
8. Will I need to empty the water bucket often?
Yes. If you’ve experienced flooding you can expect it to fill up fast. Consider getting a drain hose to allow it to run continuously.
9. How will I know when the area is completely dry?
After flooding, you want to make sure no excess humidity remains. Use a hygrometer and moisture meter to ensure all water is gone.
10. When should I call a water restoration professional?
If you notice water has seeped into walls, insulation, between flooring, or into HVAC units it may be time to call in a professional. If you’re not seeing results within a few days it won’t hurt to seek some help either.
When to Hire Professionals
If flooding has affected walls, flooring underlayment, or HVAC systems, it’s time to call in the professionals. A professional restoration company has powerful drying equipment and knowledge to quickly restore your home.
Attempting DIY restoration can sometimes cause more damage. Restoration professionals have the knowledge and tools to get your home dried out and back to normal again quickly.
Follow this step-by-step guide to learn how to use a dehumidifier after flooding, from hour one all the way until the job is complete.
Step 1: Assess for Safety Before Entering
Safety first. Before you enter your home with any equipment, make sure it’s safe. Check for structural damage like sagging ceilings, bowed walls, or water around electrical outlets. Shut off power at the breaker box if there’s any chance of water coming in contact with electricity. Water and electricity don’t mix.
Put on rubber boots, rubber gloves, and a protective face mask. Floodwater contains bacteria, sewage, and chemicals you don’t want to breathe or touch. If you’re protected, you can work longer and stay safe while restoring your home.
Step 2: Document Damage with Photos and Videos
Capture video and take photos of the affected areas before you do anything else. Walk through each room and photograph walls, floors, ceilings, and damaged property. Your insurance company will need this info to process your claim. Take as many detailed pictures/videos as you can.
Upload the files to your cloud storage account or email them to yourself right away. You don’t want to lose that valuable documentation.
Step 3: Remove Excess Water Before Starting
You cannot use a dehumidifier instead of water extraction. The machine only extracts water from the air. If there is standing water on the floor, remove it first.
Use wet/dry vacuums, pumps, or mops to get rid of excess water. Remove as much water as you can before switching on the dehumidifier. A wet room slows down the drying process significantly.
Remove any carpets, rugs, or wet upholstered furniture you can. These items absorb water and will only prolong drying time. It’s usually easier to dispose of saturated carpets than try drying them in place.
Step 4: Select the Correct Dehumidifier for the Job
Dehumidifiers range from small room units to massive commercial models. Do not try to use a small unit meant for bedrooms in a flooded basement or family room.
For larger water-damaged areas, use a refrigerant-style dehumidifier. These units excel at warmer temperatures and higher humidity levels which you’ll likely find with flood damage. If the room is cool, use a desiccant model instead.
Desiccant dehumidifiers are more efficient at pulling moisture from the air in cool temperatures.
Rent a commercial-grade dehumidifier if the flooding was severe. Commercial models extract hundreds of pints of moisture every day. Professional restoration teams use machines that remove over 100 pints of water per day.
Step 5: Place the Dehumidifier Properly
Placement is important. Place the unit in the middle of the room when possible. This allows for air to be pulled from all directions. Leave 1-2 feet of clearance around the entire unit so air can freely flow in.
Don’t place it in corners or up against walls. Obstructed airflow diminishes moisture output.
Work on the worst room first if multiple rooms are flooded. Once the space reaches safe humidity levels, move the unit to dry other areas.
Step 6: Adjust Humidity Settings
Turn on the dehumidifier and set your desired humidity level between 30-50%. With flood damage, you’ll want to get the humidity as low as possible. Set the dial to the minimum setting your unit allows, preferably 30%.
Dry climates average 30-50% humidity on a daily basis. After flooding, that number jumps to 80% or higher. Setting the unit to a low target forces it to work harder and dry the area more quickly.
Step 7: Use Fans To Circulate Air
Box fans and high velocity fans help air circulate around the room. Set up fans in the room with the dehumidifier to move air. Face the fans toward wet surfaces and across the dehumidifier’s air intake.
Place one fan to blow air across the wet wall/floor. Position another fan so that air blows towards the dehumidifier. This creates a cycle of moving air that speeds evaporation and allows the unit to collect more moisture each hour.
Do not open windows unless the air outside is dryer than the air inside. If it’s humid outside, keeping windows open will only introduce more moisture.
Step 8: Empty the Water Bucket
If you’re using a standard home dehumidifier, there should be a small collection tank inside. After a flood, you’ll likely need to empty this bucket every few hours. When the tank reaches maximum fill, your unit will shut off. An empty unit will slow down the drying process.
If your unit has a drain port, attach a hose and place the other end in a bucket. Some models come with hoses, while others require you to purchase one separately. This allows you to continuously run the dehumidifier without stopping.
Step 9: Monitor Humidity Levels Over Time
Purchase a hygrometer to monitor humidity levels throughout the day. Hygrometers are affordable and available at local hardware stores. You can track the room’s humidity percentage as the dehumidifier runs.
The goal is to bring the humidity down below 50% relative humidity.
Consider purchasing a moisture meter to keep track of hidden moisture. Moisture meters detect how much moisture is inside the walls, floors, and wood surfaces. You can’t always see water with the naked eye. A moisture meter will tell you if water is still present even after surfaces dry.
Step 10: Continue until the Humidity Stays Low
Leave the dehumidifier running for at least one to three full days. Some severe floods can take up to a week to fully dry, depending on how much water was involved. Check your moisture meter readings each day.
When all readings return to normal and stay below 50% humidity, you can safely turn off the unit.
Case Study: Basement Flooding from Heavy Rainfall
Client: Residential customer with flooded basement (120 m²)
Problem: Outside rain water entered the basement through cracks, causing some standing water, soaked carpets, and overall humidity above 85%. Odor developed after 36 hours, and slight mold was beginning to show on lower walls.
Solution Details:
Immediately pumped out standing water with a wet/dry vacuum. Removed carpets and furniture that absorbed too much water.
Used a commercial refrigerant dehumidifier rated for over 100 pints per day.
Put the dehumidifier in the center of the room and let it breathe (1–2 feet from walls/furniture).
Set humidity levels to 30% for faster drying.
Added several high-velocity fans for air circulation across damp areas, blowing towards the dehumidifier.
Monitored using a hygrometer and moisture meter to measure both air AND wall/metal humidity.
Attached a drain hose so the customer could leave it on without having to empty the bucket.
Case study - https://www.sedgwick.com/blog/tackling-the-challenges-of-basement-flooding/
Results:
Humidity was lowered to below 50% within 48 hours.
The entire structure was dry in 5 days.
Prevented further mold development.
Saved customers from expensive repairs/remediation.
Moral of the story: Don’t wait too long. Act quickly. Use the right tools and monitor the job until complete. Using a dehumidifier with complementary air circulation will cut your drying time significantly.
FAQs:
1. How quickly should I start drying with a dehumidifier?
As soon as the bulk of standing water is gone. Mold can grow within 24–48 hours so time is of the essence.
2. Will a dehumidifier pull up standing water?
No, you need to get rid of the standing water first. Use a pump, wet/dry vacuum, or large sponge/mop to soak it up before using a dehumidifier.
3. What kind of dehumidifier do I need to dry out flood damage?
If your main concern is indoor humidity after a flood, we recommend…
Refrigerant dehumidifiers for warmer/climate conditions
Desiccant dehumidifiers for cooler environments
…and if the flooding is severe, go with a commercial-grade unit.
4. What humidity level should I set for flooding?
30% to begin with because you want the drying process to happen quickly. Afterwards, keep humidity below 50%.
5. How long do I need to run my dehumidifier after flooding?
This can vary anywhere from 1 day to over a week depending on severity. Until your readings start showing <50% on your hygrometer, you should keep it running.
6. Should I be using fans with my dehumidifier?
Yes! Fans allow for better air circulation and force moisture to evaporate quicker (making it easier for your dehumidifier to do its job).
7. Where is the best place to put my dehumidifier?
We recommend placing your dehumidifier…
In the center of the room with access to all walls
At least 1–2 feet away from walls/furniture
…Start with the room that was most affected and move from there.
8. Will I need to empty the water bucket often?
Yes. If you’ve experienced flooding you can expect it to fill up fast. Consider getting a drain hose to allow it to run continuously.
9. How will I know when the area is completely dry?
After flooding, you want to make sure no excess humidity remains. Use a hygrometer and moisture meter to ensure all water is gone.
10. When should I call a water restoration professional?
If you notice water has seeped into walls, insulation, between flooring, or into HVAC units it may be time to call in a professional. If you’re not seeing results within a few days it won’t hurt to seek some help either.
When to Hire Professionals
If flooding has affected walls, flooring underlayment, or HVAC systems, it’s time to call in the professionals. A professional restoration company has powerful drying equipment and knowledge to quickly restore your home.
Attempting DIY restoration can sometimes cause more damage. Restoration professionals have the knowledge and tools to get your home dried out and back to normal again quickly.