This project shows how to install a basement dehumidifier and drain the condensate water to the outdoors for continuous operation. A dehumidifier extracts moisture from the air and is a great way to lower the humidity in a basement. This makes the air fresher and reduces the chance for mold. I wanted a dehumidifier to eliminate any chance of rust on the tools in my basement workshop. The humidity in the basement ranged from around 40% in dry weather up to 70% in damp weather. I wanted to limit the humidity to around 50%, which is on the dry side. The question I faced is “What to do with the water?”.
How to Install a Basement Dehumidifier
Room size humidifiers have a condensate bucket that must be emptied by hand. A float switch turns off the humidifier when the bucket is full to prevent overflows. Many humidifiers also provide a threaded spigot to connect a water hose for drainage, assuming you have a floor drain or sump pump to take away the water. A daily routine of checking and emptying the condensate bucket wasn’t going to happen. I’ve got better things to do. My basement doesn’t have a floor drain or sump pump, so draining the unit with a water hose wasn’t an option… then I had an idea.
The solution was to elevate the dehumidifier above grade level and use PVC plastic pipe to drain away the water. This is possible because my house sits on a hillside and the basement is above ground on three sides.
Dehumidifier Installation Materials List
- Frigidaire FAD704DWD Energy Star 70-pint Dehumidifier (current model as of 2019)
Rated for a 1400 square foot room, 70 pints per day, digital controls, low temperature operation down to 41 deg. F, continuous drain option, automatic 35% to 85% humidity control, top air discharge.
- 5/8 inch plywood shelf, 14 inches deep by 17 inches wide.
- Two (2) shelf brackets – Simpson Strong Tie brand – type “SBV” 9 inches by 11 inches. Available at Home Depot.
- One (1) box of Simpson Strong Tie SD8x1.25 wood screws. Available at Home Depot.
- Four (4) PVC, 1/2 inch, 90 degree elbows.
- Ten (10) feet of 1/2 inch PVC pipe.
- One (1) can of PVC purple primer.
- One (1) can of PVC cement.
- One (1) 1/2 inch PVC to garden hose bibcock adapter (available at Home Depot or Lowes).
Basement Dehumidifier Installation
- Pick a location several feet above the exterior ground level that is free of electrical, plumbing and natural gas lines. I used the natural gas pipe entrance to locate and mark a position on the exterior and interior walls for the 1/2 inch PVC drain pipe.
- Cut the 14 x 17 inch plywood shelf to rest the humidifier upon from a scrap sheet of plywood. I used 5/8 inch plywood as it is strong with enough thickness for the wood screws to hold fast.
- Using a carpenters level, mark the level line on the 2×4 wall studs for the top of the shelf, at or slightly above the height where the drain line will penetrate the wall. Attach the shelf brackets to the 2×4 wall studs with the wood screws, the top of the brackets even with the level line.
- Attach the plywood shelf to the brackets with wood screws driven from the bottom of the shelf (screws are pointing upward).
- Drill a 1/4 inch pilot hole in the basement wall at the location marked for the drain line.
- With a 1/2 inch drill bit, enlarge the pilot hole to 1/2 inch. You may need a masonry drill bit if the wall is construction is stucco, brick, cinder block or poured concrete.
- Remove all wheels or casters from the humidifier.
- Center the humidifier on the plywood shelf.
- Using a tape measure, cut and dry fit (no glue) the PVC to garden hose adapter, pipe sections and 90 degree elbows. Trim and adjust the plumbing as needed.
- When your satisfied with the PVC plumbing connections, glue the sections together. PVC is very easy and fast to glue. Swab the mating ends with purple cleaner, swab on some glue and press together. The bond is permanent in a minute.
- Caulk the the PVC pipe where it exits the wall to provide a water tight seal.
The following photos will clarify the layout and fittings.
The PVC to brass garden hose adapter and other pipe fittings are shown in the photo below. The humidifier drain bucket has been removed to view the interior.
The finished PVC drain pipe connections.
The PVC drain pipe exit through the exterior wall. The natural gas pipe was used to locate and mark the PVC exit at a suitable location above ground level.
The PVC pipe just lays on top of the ground, covered with pine straw as shown in this photo. It’s important to run the line away from the foundation because a persistent wet spot can invite termites.
- Do not glue the vertical PVC pipe run to the 90 degree elbow at the wall exit. The dry fit connection is water tight because there is no pressure in the line and it’s easy to disconnect for cleaning. When I mow the yard, I swing the pipe out of the way. Take care to keep the pipe drain at least 6 feet or more from the foundation wall to discourage termites.
- Once a year, unscrew the PVC pipe drain connection from dehumidifier and pour an ounce or two so of household bleach down the pipe to kill any algae or mold that could clog the drain. I’ve never had a clog.
This Frigidaire model has a limited 1 year full & 5 year sealed system warranty (compressor, condenser, evaporator and tubing). I’ve replaced mine 4 times under warranty since I wrote this article in 2008 due to “sealed system” failure… the compressor dies. Keep your purchase receipt because in my experience Frigidaire will refund the original purchase price as it’s not worth returning or repairing. Then I buy a new one from Amazon.com (which conveniently has my receipt online so it’s never lost!) and the new unit warranty begins again.
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