Sump Pump Float Switch Types: Vertical vs Tethered

Quick answer from a licensed plumber: A vertical float rides up and down right beside the pump. It fits a small pit (10 or 11 inches, per Liberty and Wayne) but pumps a short range, about 9 inches on and 4 off on a Wayne. A tethered float swings on its cord. It needs a 14-inch or wider pit and pumps a bigger range, about 13 on and 7 off on Wayne’s tether models and Liberty’s 280- and 290-Series. Measure the pit, then pick the type your pump and pit allow.

The Switch Types Side by Side

Zoeller, Wayne and Liberty each build their residential sump pumps with more than one kind of float. This table is only what their own sheets and manuals print:

Two patterns stand out. Vertical floats run in a smaller pit and pump a shorter range, so the pump starts more often. Tethered floats need a wider pit because the float swings in an arc, and they move more water per cycle. Liberty says as much about its own VMF pumps: they “may be used in a minimum 10″ diameter sump; however, a larger diameter basin is preferred as it allows for a longer pump cycle and reduced float switch cycling.”

What “Piggyback” Means

A piggyback switch has its own cord and plug. The switch plugs into the wall, and the pump plugs into the back of the switch’s plug. Zoeller describes its Switch Mate as converting “a nonautomatic pump into an automatic pump by plugging the float into an wall outlet and plugging the pump into the back of the float’s plug (hence the name “piggyback”).”

The practical upside is that the switch is a separate, replaceable part. Liberty’s manual says that on its piggyback models, “in the event of float switch failure, the pump cord can be separated and plugged into the electrical outlet, directly bypassing the switch.” A pump plugged in that way runs until you unplug it, so stay with it, and do not let it run dry.

Which Type Should You Choose?

• Measure the pit first. Under 14 inches across, the makers list a vertical float or, on Zoeller, a snap-action float on a rod: Wayne’s vertical-float pumps go in an 11-inch or larger basin, Liberty’s VMF models in a 10-inch one, and Zoeller says its M73 fits “pits as small as 10″ in diameter.” A tethered switch needs 14 inches (Wayne, Liberty) and Zoeller’s Switch Mate needs 18.
• Pick the longer cycle if you have the room. Liberty says a larger basin allows “a longer pump cycle and reduced float switch cycling.” In a 14-inch or wider pit, a tethered switch gives that longer run.
• Want to replace the switch without replacing the pump? Choose a piggyback model. Wayne’s manual says “The vertical float switch is not replaceable,” while its tether switch is a separate part it tells owners to replace every two years.
• Check the voltage and amps. A piggyback switch carries the pump’s current, so it has to match the pump’s voltage and its rating has to cover the pump. Zoeller sells its Switch Mate as the 115 V 10-0034 (“13 amp max”) and the 230 V 10-0035, and Liberty’s float-control sheet lists every switch by maximum horsepower, amps and volts. The pump’s own nameplate has its voltage and amp draw.

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Electronic Switches

The switch lists we read (the repair-kit table in Wayne’s sump manual, Liberty’s Float Controls sheet and Superior Pump’s accessory list) do not include an electronic sump switch, and every piggyback switch in Zoeller’s switch category is a float, so this guide covers float switches only. If you buy an electronic switch from another maker, make sure its amp rating covers your pump’s nameplate and follow that maker’s instructions.

Brand-by-Brand Replacement Guides

The switch that fits depends on the model. Zoeller’s built-in switch is a service part (see our Zoeller float switch guide), Wayne sells a float kit rather than a switch for its vertical models (see our Wayne float switch guide), and Liberty’s model number tells you the switch type (see our Liberty float switch guide). For the check valve on the same discharge line, see our sump pump check valve guide.

FAQ

What is the difference between a vertical and a tethered sump pump float switch?

A vertical float rides up and down beside the pump, so it fits a smaller pit and pumps a shorter range. Wayne’s vertical floats turn on at about 9 inches and off at about 4. A tethered float swings on its cord, needs a wider pit and pumps a larger range. Wayne’s tether switch turns on at about 13 inches and off at about 7.

What size sump pit does a tethered float switch need?

Wayne and Liberty list a 14-inch minimum basin for their tethered switches, and Zoeller’s Switch Mate piggyback float is for 18-inch minimum basins. Vertical-float pumps go in smaller pits: 11 inches for Wayne, 10 inches for Liberty VMF models.

Can I replace a vertical float switch on a sump pump?

It depends on the maker. Wayne’s manual says its vertical float switch is not replaceable, though it sells a float kit. Zoeller’s built-in switch is a service part it tells owners to leave to its authorized service centers. Piggyback switches are separate parts that unplug and can be replaced.

What does piggyback mean on a sump pump switch?

The switch has its own plug. It plugs into the wall and the pump plugs into the back of it, so the switch turns the pump on and off. Zoeller uses a piggyback switch to make a nonautomatic pump automatic.

How often should a sump pump float switch be replaced?

Wayne tells owners to replace its tether switch every two years. Zoeller says to test the system at least every three months, and Liberty lists a quarterly check of the float switch.

Why Trust Plumbing Picks

Plumbing Picks is written by a licensed Georgia journeyman plumber. Every part number, size, setting and fit on this page comes from the manufacturer pages and documents listed below, which we opened and read; nothing here comes from hands-on testing. Nobody pays to be included here. More on who writes this and how we pick.

Sources

• Zoeller: “What Turns Your Pump On?” Model 53 switch comparison (FM3247)
• Zoeller: Model 53 Sump Pump
• Zoeller: Model 57 Cast Iron Sump Pump
• Zoeller: Model 63 Sump Pump
• Zoeller: Model 73 Sump Pump
• Zoeller: Model 98 Sump Pump
• Zoeller: Installation instructions, 3-year warranty models (FM2676)
• Zoeller: Switches (accessories and parts)
• Zoeller: 15′ 13 Amp Single Piggyback Variable Level Float Switch (10-0034)
• Wayne: CDU800
• Wayne: SPF50
• Wayne: WST30 (WST33)
• Wayne: CDT50
• Wayne: Submersible Sump Pump installation manual (600002W-001 F)
• Liberty Pumps: 230-Series sales sheet
• Liberty Pumps: 250-Series sales sheet
• Liberty Pumps: 280-Series sales sheet
• Liberty Pumps: 290-Series sales sheet
• Liberty Pumps: Installation manual 7035000 (250-, 280-, 290-Series)
• Liberty Pumps: Float Controls sheet
• Superior Pump: products and accessories list
• Superior Pump: 92010 Piggy-Back Vertical Float Switch
• Superior Pump: 92000 Piggy-Back Tether Float Switch

Bottom Line

Measure the pit before you buy. Under 14 inches, the makers list a vertical float (or, on Zoeller, a snap-action float on a rod); wider than that, a tethered float gives longer, fewer cycles. If you want a switch you can replace on its own, choose a piggyback model, and match its voltage and amp rating to the pump nameplate.