Updated 2026-10-18
Both lift groundwater out of the same pit. The difference is where the motor lives: up in the air on a column, or down in the water in a sealed case. That one choice decides how the motor is cooled, how loud the pump is, what pit it needs and what happens when the pit overflows.
Best overall
Submersible, vertical float
Cooled by the water it pumps, quiet under a lid, and published for pits as narrow as 10 to 11 in.
Best value
Pedestal in a dry, open pit
The cheapest end of the published price band, with the switch and rod in reach above the cover.
Best for a finished basement
Cast iron submersible + battery backup
Quiet, heat-dissipating housing, and a backup that needs no connection to the drinking water.
| Factor | Pedestal | Submersible |
|---|---|---|
| Motor position | Above the pit cover, on a column | On the pit floor, under water |
| Motor cooling | Air (Zoeller 81/82/84) | Sump water through the housing; oil-filled on many |
| If the pit overflows | Motor must stay out of water, spray and high humidity | Built to run submerged |
| Published minimum pit | 12 × 18 in. (Wayne) to 18 × 22 in. (Zoeller) | 10 in. (Liberty VMF) to 14 in. (Liberty tethered) |
| Switch | Float on a rod with adjustable stops | Tethered (wide-angle) or vertical float |
| Factory switch levels | 2-1/2 in. off, 10–12 in. on (Zoeller) | 4 in. off, 9 in. on (Wayne vertical float) |
| Housing | Thermoplastic (81, 82) or cast iron (84) | Thermoplastic, cast iron, finned aluminum |
| 1/3 HP output at 10 ft, Wayne | 2,700 GPH (PTU33) | 2,718 GPH plastic, 3,060 GPH cast iron |
| Warranty examples | 1 yr (Wayne PTU33), 2 yr (Zoeller 81/82/84) | 1 yr (Wayne SPF33) to 5 yr (Wayne CDU980E) |
| Pump only, published band | $80–$800 | $90–$1,000 |
Pedestals are not automatically the small-pit pump
Zoeller's pedestal data sheet lists the cooling as air and the install manual says the unit is built for indoor use with the motor above the pit cover and protected from water, spray and high humidity. A pedestal is a dry-motor pump. If the pit backs up to the rim, or the room floods, it is the first thing to lose.
A submersible goes the other way. Zoeller's cast iron family uses a sealed, oil-filled motor in a heat-dissipating body. Liberty says the finned aluminum housings on its 230 and 450 series cool 225% better than its own cast iron models, because more metal touches the sump water. Long run times in a wet spring are what these designs are built for.
On noise, the layout explains most of it. A pedestal motor runs out in the room, while a submersible runs under water and a pit lid. None of the makers we read publishes a sound level for either, so judge it on site. Service life is similar: cost guides print life spans in years, and none of the manufacturer documents we read does. The hard numbers are warranties, and they follow the build, not the layout. Wayne gives 1 year on its thermoplastic pedestal and its thermoplastic submersible, 3 years on the cast iron CDU790 and 5 on the CDU980E.
The pit usually decides this before the budget does, and the switch decides the pit. Put your measurements into the check below; it compares them with each maker's published minimum. It does not size the pump. Flow at your head and the inflow rate are the job of the sump pump sizing calculator.
Pre-filled with a 14 in. by 18 in. pit, a common size in older basements. Measure the inside diameter at the narrowest point and the depth from the floor of the pit to the slab.
Layouts that fit
4of 6
Rod float (pedestals). A float rides a vertical rod through the switch arm, and two stops on the rod set the cycle. Zoeller's manual sets the lower stop within 8 in. of the switch arm for about 2-1/2 in. off and 10 to 12 in. on, and says to move it closer for faster cycling. The rod has to stay vertical: if it binds, the pump does not start.
Tethered or wide-angle float (submersibles). A float on a short cord swings up to switch on. It gives a long pumping range but needs room to swing, which is why Liberty publishes 14 in. for these models and asks that the float stay clear of the pit walls.
Vertical float (submersibles). The float slides on a guide beside the pump. Liberty's VMF version is driven by a magnet, with no switch arm and no rubber boot to crack, and goes into a 10 in. pit; Wayne's vertical-float pumps list 11 in. with 9 in. on and 4 in. off. Pressure-diaphragm switches and electronic level sensors also exist (Superior Pump fits a diaphragm switch to its 92036 utility sink pump), but we did not find a sump model sold with one and a published pit minimum, so take that figure from the model's own manual.
IPC 2021 §1113.1.2 wants a pit not less than 18 in. in diameter and 24 in. deep unless otherwise approved, with a solid floor, access and a removable cover strong enough for the area. §1113.1.4 asks for a full-flow check valve on the discharge (on one- and two-family dwellings, only the check valve is required, without the gate valve) and discharge pipe no smaller than the pump's outlet tapping. Those numbers apply where your authority having jurisdiction (AHJ) has adopted that edition. In that case the small pits above are an existing-pit problem; a new pit dug under permit already clears every pump on this page.
Right for an open, dry pit in an unfinished space where nobody minds the motor hum. The switch, rod stops and motor are all above the cover, so a float that hangs can be seen and freed without fishing in the water.
Against it: the motor cannot get wet, the column sits in the middle of the pit, and the lid has to pass the column. Do not read "easy to service" as rebuildable either: Zoeller's pedestal manual says to consult the factory and not disassemble the pump.
Right for most basements, finished or not. Cooled by the water it moves, quiet under a lid, published for narrow pits with a vertical float, and it keeps running if the water rises over it.
Against it: every check means lifting it out, so plan a union on the discharge. Zoeller's install sheet puts a combined check valve and union just above the pit for exactly that. A tethered float needs swing room; Liberty asks 14 in. against 10 in. for its vertical float.
Pedestal or submersible, the primary pump stops when the power does, which is usually when the storm is filling the pit. The two backup families answer that differently, and only one of them touches the drinking water.
| Factor | 12 V battery backup | Water-powered backup |
|---|---|---|
| Driven by | Deep-cycle battery on a charger | City water pressure, no electricity |
| Run time, published | Liberty 441: 4.25 h continuous, or up to 6 days cycling 4 times an hour (10 gal at 10 ft) | As long as the water main holds pressure |
| Continuous run, Zoeller table | 6 to 7 h; 48 h+ at a 10% duty cycle | Not battery-limited |
| Fresh water used | None | Liberty SJ10: removes 2 gal per 1 gal used |
| Supply pressure | Not applicable | SJ10: 20 to 100 psi accepted, 30 psi recommended minimum |
| Supply line | None | 3/4 in. inlet (Zoeller FLEX, Liberty SJ10) |
| Backflow device | None | RP/RPZ where the code requires it (see below) |
| On a private well | Works | Stops when the well pump loses power |
| Pit space | Wayne ESP25N: 16 in. or larger basin | Zoeller FLEX: horizontal or vertical mount |
The ratio is where the two sources disagree. Liberty states its SumpJet removes 2 gallons of sump water for every gallon it uses, and Zoeller says its FLEX removes up to 2 gallons per gallon. The City of Ann Arbor tells residents the opposite way round: about 2 gallons of fresh water to move 1 gallon of sump water, charged on the water bill. Liberty says the output varies with inlet pressure and pumping head, and its manual warns that an RPZ may lower the operating pressure. Before quoting one, read the house pressure with the water pressure calculator or the steps in how to check water pressure.
A water-powered backup is a cross-connection
The unit ties the potable supply to a pit of groundwater. Liberty's SJ10 manual says that under the Uniform Plumbing Code (UPC), and under the plumbing codes of some states including Michigan, installation requires a reduced pressure (RP/RPZ) backflow assembly, beyond the check valve built into the unit. Ann Arbor requires the RPZ to be tested by a licensed certified plumber and inspected by the city every 3 years. Under the IPC, IPC 2021 §608.1 sends the choice of device to Table 608.1; the AHJ or the water utility names it. The backflow preventer guide covers RPZ placement and the relief-port drain it needs.
One practical point for pedestal owners: the backup pump goes in the same pit, as close to the bottom as possible, and its float needs room to move freely (Liberty 441 manual). The pedestal column takes up the middle of the pit. Measure for both before buying either.
| Line item | Published band |
|---|---|
| Pedestal pump, unit only | $80–$800 |
| Submersible pump, unit only | $90–$1,000 |
| Replace a pump in an existing pit, installed | $350–$1,000 |
| Dig a new pit | $500–$1,200 |
| Add a battery backup | $150–$250 |
| Water-powered backup, unit | $200–$900 |
The bands are wide because the job is: a like-for-like swap in a sound pit is a short visit, while a new pit means breaking slab and running a discharge. Price your own hours with the job price calculator and the plumber hourly rate guide, and add the permit where your AHJ asks for one; the permit cost guide shows how those fees are built. A water-powered backup carries the RPZ and its test on top.
Before you pick the layout