Sump Pumps 101 - Resource for Homeowners and Contractors
Sump Wells and Discharges
Wells (aka: crock, basin, sump pit or well) serve as the collection basins that house the pump. The two most common types are pictured here. The well on the left has a corrugated body and an easy slip-off lid.
These are typically less preferred as they do not seal the moisture in the well from the surrounding room. They also have predrilled drain hole lines that do not really match the pitch of the drains pipes. Meaning they need to be redrilled. The type on the right is made from a much thicker mold of plastic and has a sealed lid assembly and is much easier to level.
Wells are installed with their tops flush with the floor and generally go to a depth of 22’’ or more. In the installation of french drain systems the wells are commonly perforated to allow for some drainage. If the soil is not mud or clay and is sufficiently filled with gravel then this is a wise technique as the well sits lower than the rest of the drainage and will help to keep the water that much further from the floor. In the presence of much mud or clay extra measures need to be taken to prevent the well from receiving too much debris into the well.
It is not uncommon for sump well to be used for many purposes. Sink drains, HVAC condensation drains, dehumidifier drains, door drains. Many various types of facilities eventually end up here. It is worth note that it is always improper and against code to drain sewage or dirty water into a sump well. It is also improper to discharge a sump well into sewer supply. Draining storm and rain water into sewers is what leads to the sewers being over run in a major storm. This does not mean that this is not done in many older homes as the installer didn’t think it would make much difference. Although en masse it does make a huge difference when 800 homes in a specific are all draining into the sewer drain. This is a common problem in old areas with many older home in a low or flat land area.
This brings us to the discussion of discharge lines.
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A check valve is installed just after the sump to prevent ejected water from returning to the sump well. Check valves only operate in one direction, if it is placed backwards it will not function.
It is not a good idea to discharge water onto a sidewalk or into a sewer. Discharging unto a sidewalk can lead to ice in the winter.
Discharges ideally should run at least 5-10 ft from the building’s foundation wall. If there is a slope away from the house this distance is much less important. If discharge lines are buried they should be run to a catch basin that allows for the water to over flow out, or to a pop up. These units can be very difficult to install and get them to operate correctly. It takes a lot of experience. And one is always managing frozen water and the sudden rush of water in a big rain.
Discharge lines must pitch away from the pump to stop water from resting in the line and freezing, stagnating, feeding critters etc. The discharge line size relies on the thread on the pump outflow connection. The standard size for sump pump outlet lines are 1.5″ and more rarely 2″. Sometimes you will need to take a pipe that is 2″ and size down it down to 1.5″ to keep the discharge at the same size. .
Catch Basins Or Discharge Wells
These are typically box shaped units that accept water discharged outside versus allowing the water to pour on the ground,patio, sidewalk etc. They allow water to drain further into the nearby soil away from the buidling. This permits the pipe to have a free flow away from the home versus being clogged or backup with mud, snow or ice. The catch basin (picture right) is a ubiquitous tool used to prevent this problem. In areas where the ground freezes below 14’’, like the far north, then a more robust / deeper discharge cavity should be dug and or a different design should be applied. Dry wells are also a possibility. These are pits dug 3+ ft. deep that the discharge enters into the side of. They are then filled with gravel and covered with a filter fabric to slow soil erosion into the pit. A vent pipe is then installed to the surface. The idea here is to get the discharge pipe to discharge farther below possibly frozen earth. Dry wells fail often as they become clogged with earth. It is basically unpreventable as the unit must allow water and even with fabric and stone the silt and mud eventually get through. And so it is that they must be cleaned periodically.