Quick answer
For most basement and crawl space pits, the best sump pump basin is the Mindoub 18.5 in Large Perforated Sump Pump Basin and Lid Combo, rated 4.4 stars across 36 Amazon ratings: its 48 perforations let groundwater in, and an 18.5 in diameter holds about 1.1 gallons per inch of depth, so the pump starts about half as often as it would in a 13 in pit. Buy the PetPhilia 6.5 Gal Sump Pump Basin only where a vertical-float pump must fit a tight crawl space. If radon, odor or damp air is the problem, keep your basin and buy a Jackel sealed cover instead.
Buyer's Guide
What to know before you buy.
Pit Size Sets How Often the Pump Starts
Every sump pump turns on at one water level and off at a lower one, and the basin's diameter decides how many gallons sit between those two levels. The arithmetic is short: square the diameter in inches and multiply by 0.0034 to get gallons per inch of depth. A 13 in basin gives about 0.6 gallons per inch, an 18 in basin about 1.1, a 22 in basin about 1.65 and a 24 in basin about 2. With a float that travels 5 in, that is roughly 3, 5.5, 8 and 10 gallons per cycle. A narrow pit refills that gap in seconds during a storm, so the motor starts and stops constantly, and starts are what wear out a switch and a motor. Depth matters for the same reason. Most basins in this roundup are about 15 in deep; installers commonly set pits 22 to 30 in deep so the off level still leaves water over the pump intake.
Perforated or Solid Walls
A perforated basin is open to the ground around it. Set in washed gravel, it lets water that would otherwise push up on the slab drain into the pit, which is why sellers describe it as relieving hydrostatic pressure. Choose it for a crawl space or basement with no perimeter drain tile, a high water table, or water that rises through floor cracks. A solid basin takes water only through an inlet, usually the end of a drain tile loop, and keeps silt and sand away from the pump. Choose it where drain tile already feeds the pit, and always for a sewage ejector, which must be sealed and vented. Mindoub and PetPhilia are perforated; Little Giant's WCR basin is solid with a molded inlet hub. Holes also admit soil gas, so a perforated basin needs a sealing lid more than a solid one does.
Drop-On Lid, Bolted Lid, or Airtight Cover
A lid does four jobs, and the cheap ones do only the first. Slotted drop-on covers keep toys, lint and a foot out of the pit. Bolting a gasketed cover to the rim also holds back the humid air that rises from standing water, which works against EPA's advice to keep indoor humidity below 60 percent, and the odor a stagnant pit develops. Sealed pipe and cord penetrations go further and close the pit as a radon entry route, because soil gas follows the same path in that water does. EPA recommends homes be fixed when the radon level is 4 pCi/L or more and says to consider fixing between 2 and 4 pCi/L, so test first. If the result is high, a sealed sump lid is one part of a mitigation system, and the vent flange on a cover like the Jackel SF16314-CV is where the contractor's pipe connects. None of these listings uses the word airtight, so expect to add sealant where the lid meets the rim.
Leave Room for a Backup Pump
A single pump in a pit is a single point of failure, and the hours it fails are the hours it rains. If a battery backup is in your plan, choose the basin for two pumps now, because a 13 in or 18 in basin rarely has floor space for both. Two pump bases, two floats that must not touch each other or the wall, two discharge pipes and a check valve on each take a 22 in or wider pit, and Little Giant's 22 in x 30 in basin is the only candidate here with that room. A tethered float needs still more clearance to swing, which is why PetPhilia's listing refuses tethered pumps outright and why vertical-float pumps suit narrow basins. Set the backup's float a few inches above the primary's so it runs only when the primary falls behind, and give each pump its own outlet.
Setting the Basin So It Stays Put
An empty plastic basin in wet ground is a boat. Dig the hole a few inches wider and deeper than the basin, bed it on washed gravel, and backfill around a perforated basin with more gravel so water reaches the holes without carrying silt. Set the rim flush with the slab or a hair above, never below, or the lid cannot seal. Little Giant molds an anti-flotation collar into its basin for this reason; the lighter basins rely on the backfill and the concrete patch to hold them down. Route the discharge up through the lid's flange or pre-cut opening, fit a check valve above the pump so the column does not drain back and restart it, and pass the cord through a grommet. Before you fill the pit, drop the pump in and lift the float by hand to confirm it rises or swings freely.
Who Does Not Need a New Basin, and When to Call a Pro
If your pit already works, do not buy a basin. A pump that short-cycles in a sound pit usually needs a check valve or a float adjustment, and a pit that smells or sweats needs a sealing lid, which costs less and takes an hour. A basin is the right purchase when the old liner is cracked, when there is no pit at all, or when the existing one is too narrow for the pump you want. Call a licensed plumber for a sewage ejector pit, since its basin, vent and check valve fall under plumbing code in most places and the work is permitted. Call a basement waterproofing contractor to cut a slab, tie in drain tile or set a pit below a finished floor. If a radon test reads 4 pCi/L or more, a certified radon mitigation contractor sizes the fan and vent; a lid alone is not a fix.
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