Crawl Space Sump Pumps for Durham-Area Homes: When You Need One

What are you actually seeing under the house?

Go look the day after a hard rain, when the evidence is fresh. What you find sorts the problem into one of three types, each with a different fix:

The third case is more common than people expect. A dripping supply line, a loose drain joint or a water heater leaking down into the crawl space can soak the soil in one area for months. Call for help tracing the leak first; a pump would only hide it. If the drip is coming from the heater, a water heater repair visit is the right call.

Fix the outside before you dig a pit

The U.S. Department of Energy's Building America guidance for existing crawl spaces puts exterior water control first. It calls for regrading soil so it slopes away from the house, replacing or adding drains to walks and driveways that tilt toward the foundation, and making sure gutters and downspouts carry roof water away. Where water still gets in, it recommends drain pipe around the exterior footings that discharges to daylight or a drywell.

These steps cost less than most pump installations and often solve the problem outright. A downspout that empties right at a foundation corner is one of the most common culprits, and it is easy to spot during a storm.

Drainage on your lot is your responsibility. The City of Durham says the owner of the property where a drainage system sits is legally responsible for maintaining it, including ditches and buried pipes, and that changes to a drainage system need the proper permits first. The City's Stormwater Services line (919-560-4326) takes private drainage questions, and Durham County Stormwater (919-560-7006) can help county residents figure out who is responsible for a ditch or culvert.

How a crawl space sump works

The same DOE guidance describes the usual setup: a plastic pit 2 to 3 feet deep with holes in the bottom, set at the low point of the crawl space so water drains into it before it reaches the floor, and topped with a gasketed, tight-fitting lid. A submersible pump sits in the pit and pushes water out through a discharge pipe.

That discharge line deserves as much thought as the pump. It should end outside, far enough from the foundation that the water does not circle back in, and somewhere it will not flood a neighbor's yard. It should not be tied into a sewer cleanout; sanitary sewers are built for wastewater, not groundwater. If you are unsure where water can go on your lot, the stormwater offices above can help.

What a good install includes

• A pit at the true low spot, which may not be the easiest place to reach
• A check valve on the discharge so pumped water does not fall back into the pit
• A dedicated outlet near the pit, which may mean an electrician
• A sealed lid that ties into the vapor barrier
• An optional high-water alarm or battery backup pump

Plumbers who install and service sump pumps in Durham can tell you whether your space needs a new pit or only a better pump in an existing one.

Testing the pump you already have

A crawl space pump can sit idle through a dry stretch and then fail on the first big storm. NDSU Extension engineer Tom Scherer recommends a simple routine, which works as well in the Piedmont as in North Dakota:

1. Confirm the pump is plugged in and has power.
2. Lift the lid and shine a light in. Clear any debris and make sure the pump intake is not blocked.
3. Pour water in slowly until the float starts the pump. Make it cycle on and off at least twice.
4. Listen. A pump that sounds like it is grinding gravel, or a float that is sluggish, may mean it is time for a new one.
5. Walk the discharge pipe outside and confirm it is clear and sends water away from the house.

Scherer notes that every pump should have a check valve on its outlet, since water flowing back into the pit makes the pump cycle more and wears it out faster. Worn motor bearings and a float switch that makes poor contact are common reasons pumps quit. A battery backup pump installed in the same pit runs only if the main pump fails.

How long should you expect a pump to last? InterNACHI's life expectancy chart lists sump pumps at about 7 years with regular maintenance. If yours is older than that and has never been tested, testing it before the next stormy season is a good idea.

Keeping the crawl space dry, not just drained

A pump moves liquid water. Moisture rising from the soil and humid air coming in through vents need their own controls. DOE guidance calls for 6-mil or thicker polyethylene over the entire floor, run 8 to 12 inches up the foundation walls and piers (or up to outside ground level), with seams overlapped 6 to 12 inches and taped. The sump lid should seal to that sheeting so the pit does not leak humid air into the space.

Plenty of owners take the next step and close the crawl space. Under North Carolina's residential code, Section R409.5, a closed crawl space must have mechanical drying, as the Office of State Fire Marshal summarizes. Options include a permanently installed dehumidifier rated for at least 15 pints per day, with its condensate drained to daylight or to a condensate pump, or supply air from the HVAC system, house air or an exhaust fan. The supply air option is heating and cooling work, so closing a crawl space often involves more than one trade.

After water gets in: drying out

Pump or vacuum standing water out as soon as it is safe to go under the house. The EPA says water-damaged areas and items should be dried within 24 to 48 hours to prevent mold growth.

NC State Extension's flood guidance adds several crawl space specifics. Remove and replace wet insulation. Use fans to pull air out and make sure foundation vents open and are clear. Wood decay fungi do not grow below about 28 to 30% wood moisture, but you should not close anything up until a moisture meter reads 19% or lower. Mold on joists does not by itself mean the wood will rot, but it needs cleaning.

When the water came from a broken pipe rather than rain, shut off the main first and follow the steps in our guide to the first minutes after a pipe bursts. Supply lines in vented crawl spaces are exposed to winter cold, so read up on protecting pipes from a hard freeze before January. Once the water is off, a plumber can handle the pipe repair itself.

Older houses and rural lots

Older foundations were rarely built with modern drainage details. About 30% of homes in Durham were built before 1980, compared with roughly 56% in Oxford and 71% in Roxboro, so crawl space water is a familiar problem across the region. On rural lots with a private well and an onsite wastewater system, keep sump discharge well away from both the wellhead and the drain field.

Not sure whether you have a drainage problem or a plumbing one? A plumbing inspection can rule out leaks under the house before you spend money on a pump. You can also browse the full list of services.