The best sump pit basins
The hole constrains everything else. Get it wrong and you spend the next decade choosing pumps around a basin that is too small.
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Almost everything frustrating about a sump installation traces back to the basin. A pit that is too narrow rules out tethered floats and forces short cycles. A pit that is too shallow means the pump draws down a few inches, stops, and starts again minutes later. Neither can be fixed by buying a better pump.
Sizing a sump basin
| Dimension | Typical | What it decides |
|---|---|---|
| Diameter | 18 in minimum, 24 in better | Switch type, whether a backup pump will fit |
| Depth | 22 in minimum, 30 in better | Draw-down per cycle, and therefore how often the pump starts |
| Inlet position | Set by the drain tile | Where water enters, and whether it splashes onto the switch |
| Lid rim | Standard profiles | Which covers will fit without a custom job |
A rough rule for depth: every extra inch of usable depth is one more inch of water the pump moves per cycle, and fewer cycles means a longer-lived switch and motor. The limit is that the pit floor has to sit below the drain tile inlet, which the original construction usually fixed for you.
Jackel SF20 sump basin (18 x 22 in)
An 18 by 22 inch basin, which is the practical floor for a pit you will not regret.
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| Size | 18 in diameter x 22 in deep |
|---|---|
| Capacity | 20 gallons |
| Material | Injection-molded structural foam polyethylene, one piece |
| Rim | Pre-drilled holes with metal inserts to accept a cover |
| Sealing | Gas and radon tight when fitted with a sealed cover |
| Weight | 11 lb |
If you are installing a pit from scratch, this is the size to start from. It accommodates essentially every residential submersible pump and every common switch type, and lids for it are off-the-shelf.
The one piece of advice worth repeating: if a backup pump is anywhere in your plans, buy the bigger basin now. Widening a pit later means a demolition hammer and a weekend.
What it gets right
- Wide enough for a tethered float to swing without catching the wall
- Deep enough for a long draw-down, which means fewer motor starts
- Standard dimensions, so lids and covers are easy to source
Where it falls short
- Still tight if you plan to add a backup pump later — consider going larger from the start
- Replacing an existing basin means breaking concrete
Specifications from 18 x 22 in radon sump basin distributor listing.
Perforated or solid?
A perforated basin lets groundwater enter through the sides as well as the drain tile, which is what you want when the pit is doing general water-table management. A solid basin takes water only from the connected tile, which is the right choice when you are trying to keep soil gas out — notably in a radon-mitigated house, where the pit must be sealed from the ground.
Most residential retrofits use a perforated basin with gravel around it. If radon is a factor, talk to whoever specified the mitigation before ordering.
Installing a new basin
- Set the basin so the rim finishes flush with or just above the finished floor.
- Backfill around it with clean gravel rather than soil, so water reaches the perforations.
- Connect the drain tile to the inlet properly, rather than letting it spill against the outside of the basin.
- Fit a lid from the start. An open pit in a new installation is a missed opportunity.
Sizing in more detail, including how pit area relates to inflow measurement, is in what size sump pit.
Questions people ask
What size should a sump pit be?
18 inches in diameter by 22 inches deep is the usual practical minimum for a residential pit. Larger is better, particularly if you may add a backup pump later.
Can a sump pit be too big?
Rarely a problem in practice. A larger pit means longer draw-down and fewer motor starts. The constraints are floor space and the depth of the drain tile, not the pump.
Should the basin have holes in it?
A perforated basin lets groundwater in through the sides, which is usually what you want. A solid basin is appropriate where the pit must be sealed from the soil, as in radon mitigation.
Can I replace just the basin?
If the hole is sound, yes — it is a messy but approachable job. Cutting a new pit into a slab is a different proposition and generally one for a contractor.
Sources
Read next
What size should a sump pit be?
The hole constrains everything that goes in it. Pit dimensions rule out more pumps than horsepower ever will.
The best sump pit covers
An open pit is an evaporation surface in the middle of your basement. A lid is the cheapest humidity fix there is.
The best submersible sump pumps
A submersible sits in the water it is moving, which makes it quieter, cooler and almost always the right choice — provided the pit is big enough for it.
How to install a sump pump
A like-for-like replacement in an existing pit is a two-hour job. Cutting a new pit into a slab is not, and this page is honest about which is which.
The best sump pump float switches
Motors rarely die first. Switches do — and unlike a motor, a switch is a part you can replace in twenty minutes for the price of a takeout meal.