DIY Moultrie Deer Feeder Vent: A $30 Chimney Mod to Stop Moisture Build-Up

Reading time: 6 minutes

 

In our last article, we covered what stuck moisture can do inside a deer feeder: at best, a batch of feed goes bad; at worst, mouldy corn ends up in front of the wildlife you're trying to feed. This time, we're covering how to prevent it.

When we went looking for solutions online, we didn't find much. A few Reddit comments suggested drilling holes in the lip under the lid, or tossing rice pouches in the hopper. None of it looked effective or clear enough for us.

So we designed our own: a simple chimney vent that lets warm, humid air escape on hot days. We had two rules. It had to be removable, and it had to be minimally destructive. Worst case, a replacement lid undoes the whole thing.

 

 

Why a Chimney Works

Warm air rises, and on a sunny day the air inside a feeder heats up and picks up moisture from the feed. With nowhere to go, that humid air sits under the lid. When the lid cools overnight and drops below the dew point, the moisture condenses and drips back onto the feed.

A chimney gives that warm, humid air a way out at the top, while drier air is drawn in through the feed port at the bottom. It's the same stack effect that makes a wood stove draw.

To be clear, a vent reduces moisture build-up. It doesn't make condensation impossible on a cold night. It just gives the moisture a way out instead of trapping it.

 

Tools

This is the bare minimum. Better tools (a mitre saw instead of a hand saw, for example) will make the job faster and more accurate.

• Saw
• Drill
• 2" hole saw
• Measuring tape
• Masking tape
• Marker
• Safety glasses and gloves
• Sandpaper or a deburring tool

 

 

Parts

All of it came from our local hardware store. Names are the retail names, so you can find them on the shelf.

• ABS cement
• Male Trap Adapter 1-1/2" x 7" (comes with its plastic nut)
• P-Trap 1-1/2"
• Copper Pipe Adapter 1-1/2"
• Union 1-1/2"
• Flat Waste Gasket 1-1/2"
• Strainer 1-7/8"
• Silicone (optional, recommended)

Total: about $25–30 CAD at time of writing.

 

 

Safety First

• Eyes and hands: wear safety glasses and gloves when cutting, drilling and gluing.
• Watch the heat: power-cutting plastic can melt it. Molten plastic is hot, sticky and gives off fumes. Go slow, let the blade do the work, and let pieces cool before handling.
• Respect the blade: always be careful with power tools and blades. Keep your hands clear of the cutting path and hold the piece firmly and steadily.
• Ventilate: use ABS cement in a well-ventilated area and follow the label.
• Keep it clean: do all cutting and gluing away from the feeder. Shavings and cement drips don't belong in the hopper.

 

The Build

The build is simple: two cuts from one piece, a hole in the lid, then a glued assembly.

Step 1: Cut the Male Trap Adapter

1. Make your first cut 0.5" above the thread lines. This threaded piece becomes the base of the chimney.
2. Make a second cut 1.5" above the first. This short piece connects to the top fittings.
3. The rest of the pipe is your long riser section.
4. Deburr all cut edges.

 

 

Step 2: Dry-Fit Everything

Lay the parts out in an exploded view to see how they fit together, and to confirm everything's right before any cement comes out. From the bottom up:

1. Threaded base (0.5" piece): goes through the lid. The plastic nut from the Male Trap Adapter threads on from underneath and snugs up against the inside of the lid. The Flat Waste Gasket sits on the top side of the lid.
2. Union: glued onto the threaded base. This is what makes the chimney removable. When you move or store the feeder, just unscrew the union and take the chimney off without touching the watertight seal on the lid.
3. Long riser section: lifts the outlet high enough for good airflow, without getting in the way or picking up too much of the heat radiating off the lid.
4. P-Trap 180° bend: turns the outlet back down so rain can't fall in. The short 90° piece isn't used.
5. 1.5" section: connects the bend to the Copper Pipe Adapter.
6. Copper Pipe Adapter, Strainer, then the screw-on nut: the strainer is there to keep squirrels, mice and other varmints from climbing in through the chimney and feasting on the hopper, while keeping the airflow at its maximum. Bugs can already get to the feed through the feed port, so blocking them isn't the goal.

Put the whole thing together without cement.

 

 

Step 3: Drill the Lid

Take your time here. Moultrie lids go for around $20 USD at time of writing and are easy to find in the US, but they're harder to get in Canada.

1. Mark the centre of the lid. On the inside, there's a moulded circle; your hole should land inside it.
2. Tip: drill the pilot hole first, with the pilot bit alone. In plastic, the pilot bit tends to bite and pull the hole saw in violently. With the pilot hole already made, the hole saw cuts much more smoothly.
3. Mount the 2" hole saw and cut slowly.
4. Deburr the edge.

 

 

Step 4: Final Dry Fit

Mount the uncemented assembly on the lid and confirm the fit. The threaded base should pass through snugly, with the nut tight underneath.

 

 

 

 

Step 5: Cement It

Take it apart, apply ABS cement to each connection, and put it back together.

Tip: work in sequence, from the bottom of the chimney to the top. It's the easiest way to avoid putting a piece in the wrong spot. Once it's glued, it's glued. They don't call it cement for nothing.

Let the cement cure fully (check the label) before mounting it for good.

 

Step 6: Mount and Seal

Mount the chimney on the lid, gasket on top and nut underneath. We recommend running a bead of silicone around the connection for extra protection. The joint is already pretty watertight on its own, and the lid's conical shape sheds water instead of letting it pool at the joint. Silicone just adds a margin, and it can still be peeled off if you ever need to remove it.

 

Field Testing

Airflow: we confirmed the warm air was flowing out of the chimney.

Drying test: we "soaked" the inside walls with about 100 ml of sprayed water. In full sun on an 18–20 °C day, about 64-68 °F, the inside was dry in about 1 to 1.5 hours.

That test was done with an empty feeder, which let a lot of air in through the feed port. A feeder full of corn is a different story:

• The feed blocks much of the air intake at the bottom, so the draft is weaker and drying takes longer.
• On the other hand, a full hopper has much less air space inside, so there's less humid air to condense under the lid in the first place.
• The corn itself absorbs and releases moisture, so keep checking your feed, especially after long wet stretches.

Rain test: we sprayed the lid with a garden hose, using only the Flat Waste Gasket, no silicone. No water got through the lid hole. With silicone added, you get an extra margin.

From there, the feeder was ready to go back in the field.

 

Recap

1. Cut the Male Trap Adapter 0.5" above the threads, then 1.5" above that.
2. Dry-fit the full chimney: threaded base, union, riser, P-Trap bend, short section, adapter, strainer.
3. Drill a pilot hole, then a 2" hole in the centre of the lid.
4. Dry-fit on the lid, then cement from bottom to top.
5. Mount with the gasket on top and the nut underneath, and seal with silicone.
6. Test for airflow and water, then redeploy.

 

Keep Your Feed Dry

• Check your feed regularly, especially after rain and hot, humid stretches.
• Never top up on old or damp feed; empty and dry the hopper first.
• Unscrew the chimney at the union before moving or storing the feeder.
• Check the strainer for nests and debris each season.
• Spoiled feed goes in the garbage, never dumped in the woods.

 

Don't Feel Like Building It?

If you'd rather skip the cutting and gluing, we offer a plug-and-play version for $49.99 CAD. The chimney comes fully assembled; all you have to do is drill the 2" hole in your lid (see Step 3) and mount it. Before ordering, make sure it fits your lid: it's designed for the Moultrie Green Feeder Hopper Lid, and checking fitment is up to you.

The price simply covers materials, handling and shipping; the goal is to give you an easy option.

Deer Feeder Vent

 

Missed the first part? Read Mould in Your Deer Feeder: How We Cleaned Our Moultrie 200 lb Standard to see what moisture can do inside a feeder.

 

KØLTR is not affiliated with or endorsed by Moultrie. This modification is done at your own risk and may affect your feeder's warranty.