Crawl space sump pump install in a dirt crawlspace
Like many cabins and homes built in the 1950s, our cabin has a dirt crawl space. And, like many dirt crawl spaces, ours is a damp, musty, fairly disgusting place.
The first time I ventured into our cabin crawl space, there was standing water in the space. Not good. Knowing that the ideal crawlspace mimics that of the conditioned living space of your home, I knew I had a lot of work to do, and that a sump pump install was just the beginning.
The perfect crawl space is clean, dry and sealed. Ours was not. To remedy our sick crawl space, I planned to first address the standing water and after, install a vapor barrier over the crawl space to further reduce moisture and soil gas transmission into our living space.
Crawl spaces often have several reasons for excess moisture. Our crawl space was no exception. The floor of the space was very close to the existing water level, we have no rain gutters on our cabin, and much of the yard slopes improperly toward the home. All of these issues need attention, but to start, I plan to add a sump pump to get the current water out of the space.
Common Causes of a Wet Crawl Space or Basement:
- Floor of space lower than ground water level
- Roof run-off and rain entering space (no gutters, blocked or leaking gutters, slope issues)
- Condensation of moisture from humid air in space (ventilated crawl spaces, condensation on cool surfaces or ducts)
- Lack of moisture barrier between soil and space
- Leaking plumbing
The above illustrates many of the issues contributing to our damp crawl space. Installation of a sump pump is a fairly straightforward project. Read on to see how I installed a sump pump in our cabin crawl space.
OVERVIEW | Crawl space sump pump install in a dirt crawlspace
SUPPLIES LIST | Crawl space sump pump install in a dirt crawlspace
TOOLS LIST | Crawl space sump pump install in a dirt crawlspace
- Foam Sanding Block 3M 19093 2.625-Inch by 3.75-Inch by 1-Inch Fine/Medium Grit Drywall Sanding Sponge
STEPS | Crawl space sump pump install in a dirt crawlspace
- Organize tools and supplies
- Prepare your crawl space and choose a sump basin location
- Plan drain tile layout (if using)
- Dig sump basin hole and trench for drain tile (if using)
- Prepare the sump basin for use
- Install the sump basin and drain tile (if using)
- Prepare and install sump pump in sump basin
- Attach sump cover and connect sump discharge plumbing
- Install vent plumbing and connect power cord
- Finish ground work around sump basin
- Complete discharge plumbing circuit by passing it outside the crawl space
- Connect sump pump to a power supply and test
Gather sump basin, sump pump, sump check valve, drain tile, aggregate, tools, plumbing materials, and light source.
Access your crawl space and remove debris, old lumber, and trash.
Survey the crawl space to determine the best sump basin location. In general, locate the basin in the lowest portion of the crawl space where water tends to accumulate in the space.
In addition, consider a location that allows for easy access, unit servicing and drain tile connections. For this project, I located the sump at the lowest point in my crawl space, where I had previously found standing water.
Drain tile pipe is not necessary for a sump pump system, but using it will allow water to drain quicker from a large area.
In order for your sump pump setup to move water out of the crawl space, water must have a way to enter the sump basin. A simple system could just use an open sump pit or basin installed below the desired water level that allowed water to flow into the top of the basin or pit and pumped out via the sump pump.
For practical purposes and safety, most sump pits are not open and use a lid to cover the basin. Holes can be drilled in the cover or sides of the basin to allow water to enter while still providing the benefits of a “covered” system. In this install I did drill holes in the lower portion of the sump basin to allow water next to the basin to enter.
Drain tile can be added to the system to help drain more distant areas and carry that water back to the sump basin. To set up drain tile, consider which areas of the space you would like drained and plan to install corrugated or solid drain tile from that area back to the sump basin.
For this project, most of the water was concentrated at one end of the crawl space, so I started with installing drain tile just in this area. The corrugated drain pipe tile system I used will easily allow expansion of the system later if I so choose.
At the desired location of your sump basin, begin digging a hole large enough to accommodate the sump basin and with enough extra room to allow for rock aggregate placement under and around the sump basin.
If you are using drain tiles, create trenches for the tile in the same manner – allowing enough space under and around the tile for rock aggregate. Remember to slope drain tile trenches toward the basin location to help water movement into the basin. The aggregate allows for easier water passage into the drain tile and sump basin.
If the sump basin you are using does not come with penetrations, consider drilling holes in the side and bottom of the sump basin to allow for direct water drainage into (and out of during dry periods) the sump basin.
Trench drain tile parallel to the foundation wall, 12 – 18″ away from the foundation. Dirt should not be disturbed next to foundation walls or footings and do not dig under these structures.
Foundation wall forces are distributed in parallel and at angles to the wall and its footings and undermining foundation wall support can compromise your structure and risk structural collapse. Generally, you should stay the same distance away from the footing as the height of that footing.
Contact a structural engineer if you have any concerns when digging in your crawl space — this is important!
Many sump basins are ready to use as purchased. If you plan to allow passive movement of water into the basin without the aid of drain tile, make sure you add holes to the sides of the basin if not already present. Drilling holes in the bottom is good idea as well as it allows the basin to drain if the water level falls below the level of the basin.
If using drain tile, check for drain tile access holes at the sides of the basin. If not present, cut the appropriate size hole in the sides of the basin to allow for passage of the drain tile pipes. A hole saw bit and a heavy duty 1/2″ drill works well for this.
You should also check that you can get the sump basin into the crawl space through the access you have. In my case, the access was too small for a full size sump basin. I needed a way to get it into the crawl space, and decided to cut the basin into two halves and re-assembly once in the crawl space.
To allow for re-assembly of the sump basin, I attached 1/4″ aluminum stock and the waste discs from the tile access holes (they work perfectly as their profile matches the curve of the basin) with stainless sheet metal screws to one of the two halves prior to placing it in the crawl space.
Prior to placing the sump basin, place several inches of river rock or pea gravel as drainage aggregate at the bottom of the sump hole. Drainage aggregate can be anything from gravel to sand. Smaller aggregates are likely to be more stable, but tend to get into the drainage pipe and sump basin. Most find river rock or pea gravel work well.
Now place the sump basin in the hole on top of the aggregate layer. Next place and connect the drain tile pipe to the sides of the basin. Similar to the sump basin placement, place a layer of aggregate in the drain tile trenches prior to placing the drain tiles.
Once the drain tile is laid and passed into the sump basin, fill in the space around the sump basin and drain tile with additional aggregate. To help prevent aggregate passing into the drain tile, I covered my drain tile with aluminum screen. You can also purchase drain tile that comes covered with a fabric sock.
Prepare the sump pump for use by attaching the first portion of the discharge PVC pipe. Cut a section of 1 1/2″ PVC (schedule 40) long enough to pass through the sump lid and allow for connection of the remainder of the discharge plumbing system.
Most pumps have a female threaded outlet and will require a male PVC threaded adapter on the pump side of the discharge plumbing. Also, most pump manufacturers recommend drilling a small hole in the side of the discharge pipe at a level just above the top of the pump to allow drainage of the discharge system after the pump cycle is complete.
With the attached discharge PVC, place the sump pump in the bottom of the sump basin. Make sure to clean out any debris and aggregate that might have collected in the sump basin during it’s placement.
The sump pump will sit in the bottom of the sump basin and discharge the accumulated water that enters the sump basin. Most pumps are activated by a float trigger and will not pump until the water level in the basin is high enough to trigger this float switch.
Pass the discharge plumbing stub through the sump basin cover.
Attach this discharge pipe to a combination union and check valve (green valve in photo below) and plumb the remainder of plumbing for the discharge circuit. The rubber fitting of the union / check valve prevents back flow into the sump and provides a break point for the discharge plumbing.
Next, pass the power cord for the sump pump through the basin cover (use supplied rubber seals for the cord) for eventual connection to a suitable power supply. Secure the sump cover with supplied bolts /screws. (Many covers ship with a rubber seal that should be attached to the underside of the cover before attaching to basin top.)
De-watering sump systems should be vented and venting may be required by state and local plumbing codes.
To vent the sump basin, I used the same 1.5″ pvc pipe and incorporated a rubber coupling to serve as a disconnect if needed. The vent pipe simply needs to pass through the sump cover and vent the basin to the outside air.
Once both the discharge and vent are in place, run them to the desired point to pass them through to the outside of the house. I ran the plumbing for this project allow the floor joist and through the rim joist to the outside of the craw space.
Using aggregate, I used pea gravel for this topmost layer, leveled the ground over the drain tile and around the sump basin. The top aggregate will allow for easy passage of water through and down to the drain tile and sides of the sump basin.
Plan for your desired discharge plumbing path. If passing the plumbing to the outside of the home, you may need to cut a hole through the wall of the home. I cut a hole through the rim joist. (*Warning* If unsure of a safe path for your plumbing, consult a structural engineer before cutting through foundation framing)
Once the plumbing was passed to the outside, I added a rodent screen (PVC drain guard) to the vent circuit and a right angle hose attachment fitting to the discharge circuit to temporarily direct discharge water away from the house.
Eventually, I will create a drain system for use with the rain gutters that I can direct this discharge water to as well. To finish, I sealed the passage holes with exterior caulk.
Find a suitable power supply for your sump pump. Most pumps will require a 20 amp circuit and should have ground fault circuit interruption (GFCI) protection. The GFCI protection can be at the receptacle or at the circuit breaker.
I wired mine with a GFCI circuit breaker to allow for easier re-setting of the circuit if needed. For the 1/2 HP pump I’m using, I wired a dedicated 20 amp GFCI circuit to use for the pump. I also added a utility light for the crawl space from this circuit.
Switch on your power circuit (if not already on). You can test the pump function by opening the cover of your sump basin and lifting the pump trigger. Be careful not to run the pump for any period of time without water as the pump may overheat. You can also add water to the basin to test.
The sump pump uses a water level trigger to activate and pump water out of the sump basin. After water accumulates in the sump basin and rises above the trigger level of the pump, the pump will start and move water out of the basin through the discharge plumbing. The water level will then drop and once the level of the water drops below the trigger height the pump stops.
IMAGES | Crawl space sump pump install in a dirt crawlspace
Exceeding expectations after heavy rains!
As a followup, this system was installed in the spring of 2012 and has far exceeded my expectations! This system pumped out hundreds of gallons of water throughout the spring and summer. I highly recommend the Zoeller M98 pump — it’s quiet, and more than powerful enough to quickly empty the system even during heavy rains.