Sump Pumps, Basements and Crawl Spaces in Metro Denver

Where is the water actually coming from?

Pumping water out of a pit only helps if the water is groundwater. If it is coming from a downspout, a supply leak or a backed-up drain, a pump treats the symptom and leaves the cause. Timing usually tells you which one you have.

That last row deserves its own note. Water rising from a basement floor drain is usually a blockage in the building sewer, and a sump pump will not help. That calls for drain clearing in Denver or a camera inspection of the main line.

Why Front Range foundations get wet

Metro Denver is dry most of the year, which lulls many owners into ignoring drainage. Then a quick thaw after a heavy snow or a hard summer thunderstorm sends a lot of water at the foundation in a short time. Older homes add to the risk: about 55.5% of Denver housing was built before 1980, and decades of settling can leave soil sloping toward the walls instead of away from them. Window wells that fill with leaves, downspouts that dump next to the house and basement finishing that hides small seepage all make the next event worse.

Handle the outside first

The EPA's moisture guidance comes down to the same basics: keep gutters clean and working, and make sure the ground slopes away from the foundation so water does not collect there. Practical steps include:

• Downspout extensions that carry water several feet past the foundation
• Regrading low spots along the walls with compacted soil, not mulch alone
• Clear window wells with covers where snow drifts in
• Sprinkler heads aimed away from the house and not soaking the wall

Many homes stay dry after these fixes and never need a pump.

What a sound sump setup includes

• A lined pit with a fitted lid. The lid keeps debris out and limits moisture and soil gas coming into the room.
• A check valve on the discharge. Without one, water in the pipe falls back into the pit each time the pump stops, and the pump runs far more than it should.
• Its own GFCI-protected outlet. Extension cords and shared circuits are a common reason a pump is dead when it is needed.
• A float with room to move. A float that rubs the pit wall or catches on the cord can stick.
• A high-water alarm. An inexpensive alarm tells you the pump has failed before the floor is wet.

Where the discharge belongs

Pit water should leave the house and land on your own property, far enough from the foundation that it does not soak back into the pit. It should not be piped into a floor drain, laundry standpipe or sewer cleanout. Arvada's wastewater rules prohibit sump pump discharge into the sanitary sewer, and Denver Wastewater Management, which maintains more than 1,500 miles of sanitary sewer, is the office to ask about the rules at a Denver address. Other cities and sanitation districts set their own rules, so check before connecting anything.

Keeping the line from freezing

A discharge pipe that runs across the yard or sags into a low spot can hold water and freeze solid during a cold snap. The pump then pushes against an ice plug and can burn out. Slope the line so it drains completely between cycles, keep the exposed run short, and consider a freeze-relief fitting near the house that lets water escape if the outlet is blocked. The same cold that freezes the line can freeze supply pipes in a crawl space, which our guide to preventing frozen pipes in Colorado covers in detail.

Radon and the sump pit

Colorado's health department says radon is found at elevated levels in one out of every two Colorado homes and is the second leading cause of lung cancer. An open sump pit or a bare dirt crawl space gives soil gas an easy path into the house. The department recommends testing the lowest lived-in level of the home, and says a sub-slab mitigation system is usually the most effective fix, with a sub-membrane version for crawl spaces. It also says sealing cracks is not recommended as a stand-alone technique and puts typical mitigation cost at about $1,000 to $2,000 unless the design is difficult. If you are adding or replacing a sump pump, test for radon too, and make sure any lid or membrane still lets the pump be serviced.

Crawl spaces need a dry floor and dry air

Plenty of metro Denver homes, especially older ranches and split-levels, sit partly over a crawl space. The ground under them gives off moisture constantly, even when no water is standing. The Building America Solution Center recommends covering crawl space floors with polyethylene sheeting at least 6 mil thick, overlapping and taping the seams, and running the sheet at least 6 inches up the walls and piers. That sheet acts as a capillary break and vapor barrier, keeping ground moisture and soil gas away from the joists and out of the house.

For the air itself, the EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent. If a crawl space smells musty, has damp insulation or shows mold on the framing, look for a plumbing leak before blaming the soil. A plumber can run a whole-house plumbing inspection that includes the pipes and drains running through the crawl space.

Monthly and yearly upkeep

Angi's 2026 sump pump guidance lines up with what most plumbers recommend:

• Every month, pour a bucket of water into the pit and confirm the pump starts, empties the pit and shuts off.
• Once a year, clean the pit and inlet screen and remove and clean the check valve.
• Replace the float switch about every two years.
• Plan on replacing a pump that is more than seven to 10 years old; Angi puts replacement at $300 to $800.

Late winter, before the snowmelt starts, is a good time for the yearly check.

Repair the pump or replace it?

A stuck float, a bad switch or a failed check valve is a part, not a new pump. A motor that hums without pumping, trips the breaker, smells hot or is past its expected life is usually a replacement. If the pump runs constantly in a wet season, it may be undersized for the inflow, and a plumber offering sump pump repair and replacement can size one to the pit. Owners in Aurora, Littleton and Arvada face the same choices; only the discharge rules differ.

Backup options

Storms that flood basements often knock out power at the same time. A battery backup pump sitting next to the main pump takes over when the power drops or the main pump fails. A second full pump on an alternating controller is another approach for pits that take a lot of water. Either way, test the backup with the main pump unplugged.

When the water came from a pipe

If the source turns out to be a supply line, shut off the main and dry things fast. The EPA says water-damaged areas and items should be dried within 24 to 48 hours to prevent mold growth. Our guide to the first ten minutes after a pipe bursts walks through the order of steps, and a burst pipe repair fixes the break itself. For slow leaks you cannot find, professional leak tracing saves opening walls at random. If you are not sure whether a wet basement can wait until morning, see when to call an emergency plumber.