When installing your MRCOOL DIY mini split system, you're probably thinking about clean lines, weather protection, and efficiency. And if you want to avoid ugly cover kits snaking across your siding, you might wonder: can I bury the lineset instead?
The short answer: not directly. But with the right tools and planning, there are safe ways to conceal or route it underground without voiding your warranty or damaging your system.
Let’s break it down, step by step.
🏠 Why Bury a Lineset?
Homeowners like Mark (and maybe you) might want to bury a lineset for a few reasons:
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A cleaner aesthetic (no visible lines running along the exterior wall)
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Physical protection from the elements or pets
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Routing from a detached garage, ADU, or through a landscaped area
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To avoid wall-mounting brackets on certain surfaces (brick, vinyl siding, etc.)
"I didn't want to see a bulky white cover running from the side of my house to the condenser next to my garden. It just looked wrong."
But there's a right way—and a wrong way—to do it.
🪧 MRCOOL’s Official Policy on Buried Linesets
MRCOOL does not recommend direct burial of their pre-charged DIY linesets (including the DIY35-1412C).
Why?
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Insulation breakdown: The foam wrap around the copper lines absorbs moisture when in contact with soil.
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Corrosion risk: Water + copper = long-term oxidation and leaks.
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Access issues: You can’t check buried connections easily.
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Pressure concerns: The refrigerant inside the pre-charged line can be compromised if the line is bent, crushed, or exposed to high temperatures underground.
📎 MRCOOL Installation Manual: Look for specific guidance about routing and burial.
⚠️ What Happens If You Bury It Anyway?
Let’s say you decide to bury the lineset directly in soil:
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The insulation starts to soak water like a sponge
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Condensation causes thermal efficiency loss
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Freezing and thawing seasons create soil shifts, putting pressure on the tubing
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You’ll void your warranty if the line is damaged or fails
Even a small nick underground can ruin the sealed refrigerant system, requiring total line replacement.
🛠️ How to Route the MRCOOL Lineset Outdoors (Safely)
If you still want to hide the line, you can bury it properly using conduit or choose a safer outdoor alternative.
✅ Option 1: PVC or Rigid Conduit (Buried)
This is the recommended method if you're going underground.
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Use Schedule 40 PVC (3" to 4" diameter)
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Ensure smooth bends with sweep elbows
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Cap or seal both ends to keep out moisture and pests
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Lay a gravel base to allow drainage
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Slight downward slope for water runoff
"I buried my 35ft lineset inside 3” conduit, 10” deep, with a clean-out box on each end. It worked like a charm." — Mark
✅ Option 2: Surface Mount with Line Set Covers
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Use UV-rated covers (e.g., Fortress, Rectorseal) to secure to the exterior wall
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Fast, accessible, and paintable
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Keeps foam insulation dry and protected
✅ Option 3: Shallow Trench + Protective Sleeve
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For shorter distances or temporary installations
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Use flexible insulated conduit or PVC sleeve just below grade
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Lay gravel or perforated pipe underneath to prevent water pooling
📊 Recommended Burial Specs (If You Must)
| Element | Recommendation |
|---|---|
| Depth below surface | 6" to 12" minimum |
| Conduit type | Schedule 40 PVC or sealed flex conduit |
| Drainage base | Gravel or crushed rock |
| Fitting protection | Foam wrap + sealed conduit ends |
| Elbows | Long-radius sweeps (not sharp 90°) |
Avoid: direct contact with dirt, landscape fabric, or metal piping.
🏢 Mark’s DIY Underground Route (Detached Garage Example)
"I had to get from my house to a 3-car garage 30ft away. I didn’t want to use above-ground covers across a walkway. So I built a trench."
What Mark Did:
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Dug 12" trench across lawn
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Laid gravel, then slid 35ft line through 3" conduit
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Added foam tape to junctions and capped each end
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Used vented PVC caps for minor airflow
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Finished install with cover boxes on both ends for inspection
Time spent: 4 hours
Bonus: looks invisible, no leaks, zero UV exposure
🔬 Pro Tips for Outdoor Lineset Runs
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Plan the route and measure twice
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Add 10% to your lineset length for underground slack
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Avoid pulling the lineset through sharp turns
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Use pull string + helper to guide through conduit
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Never compress or pinch the lineset inside the sleeve
"If you need to turn corners, use sweep elbows — not 90° elbows. Tight bends will damage the copper or insulation."
🥇 Final Verdict: Can You Bury It?
NO, not directly.
MRCOOL pre-charged linesets like the DIY35-1412C are not rated for soil contact and should never be buried unprotected. But with proper conduit, gravel drainage, and thoughtful routing, you can absolutely run them underground in a way that’s safe, discreet, and efficient.
"Think of it like electrical wiring. You wouldn’t bury bare copper wire, would you? Same idea here."
In the next topic we will know more about: Do You Need a Wall Sleeve or Cover Kit for Your 35ft Lineset?
