The pipe is white PVC. The fan looks like a coffee can in the attic. The manometer is a small plastic U-tube with colored fluid in it. Together they make up a working radon mitigation system, and the right combination matters more in Colorado than almost anywhere else — because altitude changes what those parts need to do.
This page is the equipment deep dive: what fan models do what, what pipe specs are correct, what manometers should read, and how Colorado's altitude changes all of it.
Radon fans — the heart of the system
A radon fan looks like a small inline duct fan. It runs continuously, drawing 50–90 watts of electricity, and creates suction in the suction point beneath the slab or membrane. The right fan depends on three variables:
- Soil type under the slab — porous gravel needs less suction; tight clay needs more.
- Foundation area — bigger slabs require more airflow.
- Altitude — Colorado fans need more power than national catalogs suggest.
Common fan models
| Model | Best for | Typical retail |
|---|---|---|
| RadonAway RP140 4-inch inline, 15–21 watts, max 0.8" WC |
Very porous gravel, small home | $120–$160 |
| RadonAway RP145 4-inch inline, 37–71 watts, max 2.1" WC |
Standard porous-gravel basement install | $150–$200 |
| RadonAway GP500 3-inch high-performance, 85–153 watts, max 4.0" WC |
Moderate-to-tight soils, multi-suction systems | $250–$350 |
| RadonAway HS-series 3-inch in / 2-inch out, 120–381 watts |
Very tight clay or sand, extreme soil conditions | $400–$600 |
All major fan brands (RadonAway, Festa AMG, Fantech) carry typical 5-year manufacturer warranties.[1]
Colorado's altitude correction — the part most national guides miss
This is where Colorado mitigation design genuinely differs from a national average. Radon fans are rated at sea level. Their performance drops with altitude:
- ~4% airflow loss per 1,000 feet of elevation.[2]
- Denver (5,280 ft): a RadonAway RP145's maximum water column rating drops from 2.1" to roughly 1.6".
- Colorado Springs (about 6,000 ft): roughly 24% drop. The RP145 maxes out at about 1.6" WC.
- Mountain towns (7,000–9,000 ft): the drop is significant enough that fans must often be upsized.
What this means in practice:
- A fan that's perfectly sized for a sea-level install may be underpowered in Colorado.
- Where a sea-level home could use a single suction point with an RP145, a Colorado home with the same soil might need either a larger fan (GP500 instead) or a second suction point.
- Contractors working only off national catalog specs are the contractors most likely to under-fan a Colorado system. The result shows up in the post-mitigation test — radon levels still above 4.0 pCi/L.
Ask your contractor which fan model they're specifying, and ask why. A good answer references your altitude, your soil type, and your slab size. "We always use an RP145" is not a good answer for a multi-point or tight-soil install at 6,000 feet.
Pipe — the simple part that still has specs
The pipe is Schedule 40 PVC, either 3-inch or 4-inch diameter. Specs:[3]
- 3-inch minimum, 4-inch preferred for most residential installs.
- All joints are sealed with PVC primer and cement.
- Horizontal runs slope 3/8 to 1/2 inch per foot back toward the suction point so condensation drains where it can't pool.
- Vertical runs are supported every 4–6 feet to prevent sagging.
- The pipe between the fan and the exhaust is under positive pressure, so any leak in that section would release radon into the surrounding space. That section must be entirely in unconditioned space (attic, exterior).
Suction points — how the system pulls air from beneath the slab
A suction point starts as a 4-inch hole cored through the slab. The contractor excavates a small pit beneath — typically 12–18 inches deep and roughly 12 inches in diameter — to give the system a place to draw soil gas from. The pipe is connected to the pit with a sealed fitting, and the slab around the pit is sealed.
How many suction points do you need? It depends on:
- Sub-slab soil communication — measured by a PFE diagnostic test.
- Slab area and footprint — bigger slabs may need more points.
- Foundation zones — split-level, tri-level, and addition slabs are separate zones.
- Soil type — tight clay reduces the radius of influence of each suction point.
A single suction point handles most Colorado basements with porous gravel under the slab. A multi-zone home (tri-level, split-level, basement plus crawlspace) typically needs two or more.
Manometers — how you know the system is working
The manometer is a small U-tube gauge (or digital pressure sensor) mounted at the suction point. It measures the pressure differential between the air outside the system and the air inside the system. The standard analog manometer has two clear tubes connected at the bottom, each filled with a colored fluid (typically red mineral oil).
What a working manometer shows:
- The two fluid columns are at different levels. The pressure under the slab is lower than the indoor air pressure, which pushes fluid down on the system side and up on the outside.
- A typical reading is 0.5 to 2.0 inches of water column offset.
- When the fan is off (power failure or fan failure), the columns equalize.
What to do when you check the manometer monthly:
- If both columns are at the same level → the fan isn't running. Call the original installer.
- If the columns show a sudden change in reading → the system condition has changed. Worth a service call.
- If the reading is steady and offset → the system is doing its job.
Operating cost and fan lifespan
A radon fan draws 50–90 watts continuously. At Colorado Springs electricity rates, that works out to $5–$10 per month in electricity. EPA pegs the typical cost at under $10/month.[4]
Fan lifespan: most manufacturers warranty for 5 years; many fans run 7–10 years before replacement is needed.[1] Replacement runs $150–$400 in parts plus 1–2 hours of labor.
Signs a fan needs replacement:
- Audible humming, rattling, or grinding from the fan housing.
- Manometer reading dropping over time.
- Visible vibration or movement of the fan housing.