Plumbing Dehumidifier and Air Conditioner Drain Lines for Your Grow


Plumbing Dehumidifier and Air Conditioner Drain Lines for Your Grow

Plumbing Dehumidifier and Air Conditioner Drain Lines for Your Grow

When setting up the perfect environment for your grow room, your plumbing and HVAC system go hand-in-hand. Setting up a drainage and water reclamation system for every HVAC device can extend the longevity of your units and recycle the moisture from the grow room for reuse.

Why You Want a P-Trap

In a fully optimized cannabis grow room, a p-trap plumbing pipe is an integral component for keeping your systems clean, extending their longevity, and reducing maintenance times. P-traps are commonly used throughout homes under sinks in the bathroom and kitchen.

In an indoor grow room, equipment that contain an evaporator coil and condenser coil require condensate drain systems. Condensate disposal requires removing the condensate from all evaporators and cooling coils.  

A p-trap is a u-shaped plumbing pipe that should be installed on your air conditioner and dehumidifiers to improve the drainage process. A PVC union connector is an alternative to plumbing glue or sealant that can connect and disconnect two pipes together for easier cleaning, maintenance, or replacement.

When your units are on, they create negative pressure which can pull air through the drain port which can cause water to sit inside of your dehumidifier or air conditioner. The water that fills the u-shaped portion of the p-trap can actually stop the negative airflow through the pipe to keep the inside of your unit free from water. 

Slope Check

When installing condensate piping, you need to make sure it has a certain slope for better function. The International Mechanical Code (IMC) dictates that condensate waste piping should have a minimum 1/8 inches of fall for every 12 inches of horizontal run. Gravity will do most of the heavy lifting when draining your units from there.


Every HVAC unit (air conditioner and dehumidifier) should have a p-trap installed. Double-check that the complete drain line from your air conditioner and dehumidifier has the appropriate slope. Any dramatic dips in slope in the condensate piping can clog the drain line and create a backup.

Small room dehumidifiers can have a condensate drain pan that must be emptied out by hand.  Many larger-space dehumidifiers have a port to allow for connecting a water hose or pipe to a drain. The water from the units can be drained into a floor drain or basement sink using gravity alone.

If your air conditioning system and dehumidifier cannot be connected to a drain, you may need to collect the condensate from the drain line in a large and heavy bucket. Keep in mind, you may need to empty out the bucket once a day.

After attaching your p-trap piping, you can make a 90-degree elbow down to the ground and another 90-degree elbow at ground-level to direct water to your drain. 

Using gravity to drain your HVAC system is one of the most efficient methods but it requires placing your dehumidifier and AC in a high position compared to where your water will be drained. 

If this is not possible, you can invest in a condensate pump to move the water up the grade through the water pipes. Or choose a dehumidifier that already has a built-in condensate pump to keep the water flow moving.

Let Plenty of Water Flow Through the Unit

After installing a brand new air conditioner or dehumidifier, you should let plenty of water flow through at first. During the manufacturing of these devices, they use a lot of oil and solder, so a lot of the drained water is going to be very   dirty for the first 100 gallons or so. Do not reclaim any of this water. 

Water Reclamation

Don’t waste any water in your grow room. Invest in a water reclamation system to reuse moisture from plant transpiration and humidity from your HVAC system. The captured and reclaimed water from the common piping system and indoor environment can be put back into the reservoir and your humidifier.

If a grow room has white calcium all over, it could mean that the grower has city or well water going into their humidifiers. The humidifier is releasing that calcium-rich moisture onto the entire grow room and the calcium is drying on everything. 

Reclaimed water systems can essentially create distilled water that doesn’t have any calcium or other minerals. Contaminated water from the condensation can be reclaimed and pumped back into the humidifier to keep it clean and working for longer. 

In our grow room, we use the Automated Reclaimed Condensate System (ARCS) by Hydrologic to reclaim and purify the condensate water that traditionally goes down the drain. The resulting water from the reclamation system is ph-balanced, ultra-low PPM, and completely free of contaminants, bacteria, and pathogens. 

Measure Twice, Cut Once

When setting up your plumbing for your dehumidifier and air conditioner, make sure to measure out the exact length that you need to cut. You will need to know the measurements between the center of one fitting and the center of the other fitting. You’ll need to find out the fitting takeoff,  the dimension from the center of the fitting to the back of the hub, cup, or threads.

A ratcheting PVC cutter or PVC pipe hand saw can cut plastic pipe. A ruler can help you make certain you have the right measurements. Mark off the measurements with a pencil so you can easily erase marks if you make any mistakes or changes. While you can make remarks, you can’t cut twice, so it’s better to measure your pipe twice and cut once.

Cleaning and Maintenance

HVAC systems including an air conditioner and a dehumidifier can produce a surprisingly high amount of water per day, especially during the summer months. As a result, most air conditioning service calls are to fix an HVAC water leak caused by condensation. Leaks and water stains can be caused by a clogged condensate drain line causing the water to back up and flood the unit.

Drain lines can clog due to dust particles or bacteria that causes growth of mold, mildew, and algae to form in the condensation drain. Mold growth that is stuck in the drain can feed off airborne organic particulates and create tons of mold spores, which can negatively affect the indoor air quality and worsen respiratory issues from the mold exposure.

If you want to prevent the buildup of debris in the dehumidifier and air conditioner condensate drain line and indoor mold growth, perform routine maintenance  on your condensate drain pipe. A wet vac or air compressor can help you remove the clog from the drain. Ensure you do not damage your PVC pipe which could lead to additional water damage. 

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