Sump Pumps & Cellar Drainage
A cellar floor in a Manhattan building is usually lower than the sewer it has to drain into. Nothing leaves by gravity, which means something has to pump it.
Below the sewer, and what follows from it
The sewer in the street sits at a fixed depth. Cellar floors, storefront basements and the vault space under the sidewalk generally sit below it. That single geometric fact governs everything about drainage down there: water arriving in a cellar cannot flow out, it has to be lifted.
It also means that when the sewer surcharges in heavy rain, the cellar is the lowest opening in the system and the place the water will look for first.
Three different pumps, often confused
| Sump pump | Sits in a pit and removes groundwater and seepage. Handles clean water only |
|---|---|
| Sewage ejector | Lifts waste from below-grade fixtures up to the house drain. Sealed basin, vented, handles solids |
| Condensate pump | Small unit removing water from cooling equipment. Frequently the cause of a mystery wet patch near a mechanical room |
They are not interchangeable. Running waste through a sump pump destroys the pump and creates a health problem; putting an ejector in an open pit puts sewer gas into the cellar.
Where the water is coming from
Worth establishing before choosing a remedy, because three different sources need three different answers.
- Groundwater rising through the slab. Steady, worst in wet seasons. A sump and pit is the right answer.
- Sewer surcharge backing in through a floor drain. Sudden, during heavy rain, and it is not clean. A pump does not address this; the answer is a valve on the drain line.
- Surface water coming in at a sidewalk hatch, an areaway or a storefront threshold. Arrives fast during a storm. The fix is keeping it out, not pumping it after it is in.
What we specify and why
- Cast iron or bronze bodies over plastic where the pump runs often. They dissipate heat and last
- A float arrangement that cannot hang up on the pit wall, which is the most common reason a pump that works fine on test does nothing during a storm
- A check valve so the discharge does not run back into the pit and cycle the pump to death
- A proper discharge route that is legal and does not simply put the water somewhere it returns from
- Backup. A battery or water-powered backup matters because the storms that need the pump are the storms that take the power out
- An alarm, because a pump that has failed silently is discovered by the water
Pour a bucket of water into the pit and watch. The pump should start, clear the pit and stop cleanly. Doing that twice a year, and before any forecast heavy rain, catches nearly every failure that would otherwise be found the hard way.
Need this doing?
Call and describe the problem. You will get the price before anyone starts.