Best Condensate Pump (2026): Furnace, AC and Boiler

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Choose by the appliance and discharge route: Compare the Little Giant VCMA-20ULS for maker-approved condensate applications within its 140°F water limit. The DiversiTech FP-22 is designed for acidic, high-temperature furnace condensate, but its continuous-temperature and flow documents disagree. The CP-22LP is an AC/dehumidifier option for tight spaces; confirm the actual clearance. Use gravity drainage when the appliance instructions and drain location allow it.

Confirm these before buying: a maximum lift is not usable flow at that height, an overflow switch protects the appliance only when correctly connected and tested, and a high-temperature or acidic rating does not establish approval for your water heater. Little Giant calls for technically qualified installation and servicing. Use the exact appliance and pump manuals together.

Our general condensate option: the Little Giant VCMA-20ULS condensate pump with overflow switch. Check the Little Giant VCMA-20ULS on Amazon

A condensate pump collects the water that drips off an air conditioner coil, a high-efficiency furnace, a condensing boiler or a condensing water heater, and pumps it up and out when there is no floor drain low enough for gravity. Check appliance approval, actual flow at the required head, temperature, condensate acidity and an overflow protection plan. This guide compares three tank pumps using the makers’ pages and manuals, and shows the document conflicts that affect selection.

Condensate Pumps Compared

Scroll the comparison sideways; pump names stay visible. With a keyboard, focus the table and use the arrow keys.

Pump	Max condensate temp (maker)	Max lift (maker)	Flow (maker)	Tank	Overflow switch	Safety listing (maker)	Warranty (maker)
Little Giant VCMA-20ULS	140°F	20 ft shut-off	80 GPH at 1 ft, 48 at 10 ft	1/2 gal	Yes, NO/NC	CSA certified to US and Canada standards, per Little Giant’s page	12 months
DiversiTech FP-22	190°F max inlet; continuous: 170°F instructions / 165°F 2021 sheet; confirm	22 ft	126 GPH max (page); 1.6 GPM = 96 GPH at zero head (instructions)	0.5 gal	Yes	Not UL listed, per DiversiTech’s spec table	3 years
DiversiTech CP-22LP	160°F maximum inlet; 140°F continuous duty	22 ft	132 GPH max (page); 1.6 GPM = 96 GPH at zero head (instructions)	1/3 gal (page); 3/8 gal (data sheet)	Yes	UL listed, per DiversiTech’s spec table	3 years

Figures from Little Giant’s VCMA-20 spec sheet and owner’s manual and DiversiTech’s FP-22 and CP-22LP product pages, installation instructions, data sheets and warranty page. The selected linked offers were sold by Amazon.com and in stock when checked on October 8, 2026. Offers change; recheck the exact model, voltage, seller and included tubing before ordering.

Match the Pump to the Appliance

Air conditioner coil, dehumidifier or approved condensing furnace: the Little Giant VCMA-20ULS, wired to shut the equipment down on overflow.
High-efficiency furnace with hot, acidic condensate: compare the DiversiTech FP-22. Its instructions give 170°F continuous duty and 190°F maximum inlet, while its 2021 sheet gives 165°F continuous. Confirm the limit with DiversiTech for your exact unit, especially above 165°F; the higher figure is not resolved here.
Condensing boiler: Little Giant says the VCMA-20 is suitable for condensing furnaces and condensing boilers, with a 140°F limit and a flushing step for acidic condensate. DiversiTech’s documents for the FP-22 name high-efficiency furnaces; boilers appear only in its Amazon listing title.
Condensing tankless water heater: none of the Little Giant or DiversiTech documents we read names water heaters, and Rheem’s RTGH manual describes gravity drainage and neutralization. This guide does not establish pump approval for that heater. If gravity drainage is impossible, obtain an approved drainage design from the heater’s maker before buying a pump.
Short cabinet or under a unit: compare the CP-22LP after checking the physical unit, inlet approach and service space. The page says 4-3/8 inches tall; its 2026 sheet gives 11.8 × 5.9 × 4.9-inch dimensions without labeling the axes.
Heat pump water heater: it produces condensate, but use the heater’s approved drainage arrangement and pump specification when needed; see our heat pump water heater picks.

Acidic condensate: condensing gas appliances make acidic condensate. Rheem’s RTGH tankless manual, for example, says the condensate is known to be acidic and recommends an external neutralizer, and Little Giant says to flush its tank so acid does not pit the pump. Follow your appliance manual and local code on neutralizing before the drain. Tank flushing does not replace a required neutralizer.

Installation Checks for Your Technician

These are planning checks, not a substitute for the exact installation manuals. The inlet and discharge dimensions below are Little Giant’s VCMA instructions; do not apply them automatically to every model. Disconnect power to the appliance and pump before wiring or servicing, as the applicable manuals direct.

Remove the shipping insert. Little Giant packs a cardboard insert to hold the switch in shipping; its manual says leaving it in will cause the pump to overflow.
Flush the system first. Little Giant says to let an air conditioner cycle several times into a separate container to flush residual oils before you connect the pump.
Set the inlets. Run the drain lines into the inlet openings 1 to 3 inches without blocking the float, and cap unused openings, per Little Giant.
Run the discharge up, then down. Little Giant says to use 3/8 inch ID maximum tubing, run it straight up no more than 75 percent of the pump’s total head, slope it down slightly at the top, and route it to a drain.
Have the overflow circuit connected and tested. On the VCMA-20ULS it comes set to shut down the equipment on high water; it can be rewired for an alarm. Little Giant’s manual says to connect the two switch leads in series with the thermostat circuit, on a Class II low-voltage circuit, and not to confuse them with the line-voltage power conductors. DiversiTech’s instructions say to shut off power to the appliance and pump, then connect its switch in series with the appliance’s 24 V shut-down circuit.
Support the pump and piping, which Little Giant says prevents broken piping and bearing failures. Its manual also says the pump is for indoor use only and must not go inside an air plenum.
Commission the system. Have the technician test both pumping and the connected high-water shutdown or alarm using the exact manual’s procedure. Little Giant says to inspect and test the system every six months, more often in heavy use. A present but unconnected switch is not a working shutdown.

General HVAC and Condensing-Boiler Option

Little Giant VCMA-20ULS (554425)

115 V, 1/30 HP, 1.5 A · 1/2 gallon tank · 80 GPH at 1 ft, 70 at 5 ft, 48 at 10 ft · 20 ft shut-off · 3/8 in. OD barbed discharge with built-in check valve · tubing not included in 554425, per the maker · three 1-1/8 in. inlets · overflow detection switch, NO and NC · max water 140°F · 6 ft cord · 5 lb · 12-month limited warranty

Little Giant’s VCMA-20 is a half-gallon tank pump with a vertical pump design. The spec sheet lists AC, refrigeration and dehumidifier equipment, and says it is also suitable for high-efficiency oil and gas-fired condensing furnaces and condensing boilers. The ULS model adds an overflow detection switch, set from the factory to shut down the equipment if the tank fills, or rewired to run an alarm you buy separately.

Little Giant lists 80 gallons per hour at 1 foot of lift, falling to 48 at 10 feet and zero at its 20 foot shut-off, with a 140 degree F maximum water temperature. Its manual adds one note for gas furnaces: flush the tank with fresh water routinely so acidic condensate does not pool and pit the pump. The warranty is 12 months from purchase, per the manual; Little Giant’s warranty policy limits it to the original purchaser and to pumps bought from Little Giant or an authorized seller.

Overflow switch can shut down the equipment, per Little Giant
Suitable for condensing furnaces and boilers, per Little Giant
Check valve built into the discharge
Three inlets

140°F max water temperature
12-month warranty; DiversiTech lists 3 years on its pumps
Overflow circuit needs qualified wiring and an operation test

Verdict: A general tank-pump option for approved equipment within its flow and temperature limits. Order compatible discharge tubing separately for model 554425 and have its overflow circuit connected and tested.

Check the Little Giant VCMA-20ULS on Amazon

Best for Hot, Acidic Condensate

DiversiTech Asurity FP-22

120 V, 1/30 HP, 1.9 A · 0.5 gallon tank · max flow 126 GPH on DiversiTech’s page (1.6 GPM at zero head in its instructions) · 22 ft max lift · 190°F maximum inlet; continuous duty 170°F in instructions / 165°F in 2021 sheet; confirm before use near the limit · designed for acidic and high temperature applications · four inlets with built-in P-traps · safety overflow switch · LED indicators · check valve · 4.8 lb · 3-year warranty · listing: 20 ft of 3/8 in. tubing

DiversiTech built the FP-22 for the hard case: it says the pump is designed for acidic and high-temperature applications, and its spec table names high-efficiency furnaces as the application. Its page says it handles condensate up to 190 degrees F and has steam-resistant electronics. The installation instructions are more exact: 170 degrees F continuous duty, 190 degrees F maximum inlet temperature, and not suitable for contact with steam or gases above 190 degrees F. DiversiTech’s 2021 data sheet gives 165°F for continuous duty. Do not assume the 170°F figure resolves that conflict; ask DiversiTech to confirm the applicable limit for your exact unit before using it near the limit. The pump has a safety overflow switch, LED status lights and four inlet holes with built-in P-traps. Max lift is 22 feet. The page lists 126 GPH maximum; the instructions give 1.6 GPM at zero head, or 96 GPH (our arithmetic). The 2021 sheet repeats the FP-22 label beside both 126 and 144 GPH. Those documents do not establish one consistent flow rating. Confirm the current performance curve for your exact pump and route before sizing it.

Note one line in DiversiTech’s own spec table: it shows the FP-22 as not UL listed, where it shows the CP-22LP as UL listed. If your inspector wants a listed pump, ask before you install it. DiversiTech’s warranty page lists 3 years on pumps, for purchases from DiversiTech or an authorized retailer, and excludes damage from improper maintenance, accident or misuse and normal wear; the instructions word it as 36 months from the distributor’s sale to the contractor. The Amazon listing adds 20 feet of 3/8 inch discharge tubing in the box.

190°F maximum inlet temperature, per DiversiTech
Designed for acidic applications, per DiversiTech
Built-in P-traps on the inlets
LED status and overflow switch

DiversiTech’s spec table lists it as not UL listed
Higher 1.9 A draw than the Little Giant
Continuous-temperature and flow ratings disagree across documents
DiversiTech’s documents name furnaces, not boilers or water heaters

Verdict: A candidate for acidic furnace condensate after confirming the exact unit’s continuous-temperature limit, flow at your required head and acceptance of its safety certification. It is not our approved tankless-heater recommendation.

Check the DiversiTech FP-22 on Amazon

Best Low-Profile Pump for Tight Spaces

DiversiTech Asurity CP-22LP

120 V, 1/30 HP, 1.9 A · low profile: page says 4-3/8 in. tall; 2026 sheet gives 11.8 × 5.9 × 4.9 in. without named axes · removable reservoir: 1/3 gallon on the page, 3/8 gallon on the data sheet · max flow 132 GPH on the page (1.6 GPM at zero head in the instructions) · 22 ft max lift · 160°F maximum inlet temperature, 140°F continuous duty, per the instructions · 3-year warranty · overflow switch · LED indicators · removable check valve · reversible deck · four inlets · UL listed (DiversiTech)

When the pump has to fit under a unit or in a short cabinet, height is the spec that counts. DiversiTech’s page says the CP-22LP is only 4-3/8 inches tall. Its 2026 data sheet lists 11.8 × 5.9 × 4.9-inch dimensions without naming the axes, and an inlet height of 1.75 inches from the base. Do not treat 4-3/8 inches as a guaranteed installed clearance: confirm the unit’s dimensions, the drain’s approach to the inlet, discharge bends and access for reservoir removal. The reservoir comes out for cleaning and holds 1/3 gallon per the page, or 3/8 gallon per the data sheet. The pump has a built-in overflow switch, LED status lights and a removable check valve.

DiversiTech’s page says it suits condensate up to 160 degrees F. The instructions give 140 degrees F continuous duty and 160 degrees F maximum inlet temperature, under a heading that says the rating is not tested for hot water, and they name air conditioners and dehumidifiers as the appliances it serves. The maker gives a 22-foot maximum lift; that is not a promise of usable flow at 22 feet. The page lists a maximum flow of 132 gallons per hour; the instructions and data sheet list 1.6 gallons per minute at zero head, which is 96 gallons per hour (our arithmetic). DiversiTech’s warranty page lists 3 years on pumps. Reservoir volume alone does not determine cycling; float settings and incoming flow also matter. Check pumping capacity and service access rather than choosing by tank size alone.

Low-profile design; verify installed clearance
Removable reservoir for cleaning
UL listed in DiversiTech’s spec table
Overflow switch and LED status

Smaller reservoir than the other two
140°F continuous duty, 160°F maximum inlet
Not described for acidic condensate

Verdict: Compare for an AC or dehumidifier where the confirmed inlet, pump and service clearances fit. Its limited-height design does not approve it for acidic condensate or a water heater.

Check the DiversiTech CP-22LP on Amazon

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Before You Buy

Check the condensate temperature. Little Giant lists a 140°F maximum. CP-22LP instructions give 140°F continuous / 160°F maximum inlet. FP-22 instructions give 170°F continuous / 190°F maximum inlet, but the 2021 sheet gives 165°F continuous. Obtain clarification before using FP-22 near that limit.
Check the lift. Measure the vertical rise and account for the actual tubing route. Use the exact pump’s performance curve to check flow at the required head, not its maximum-lift headline. Resolve conflicting FP-22 ratings before sizing.
Get an overflow switch. All three have a high-water switch; have its correct low-voltage circuit connected and tested for the intended shutdown or alarm. The switch’s presence alone is not overflow protection.
Plan the drain. Know where the discharge will go and whether your appliance or code calls for a neutralizer.
Plan cleaning. Little Giant’s manual gives a cleaning routine; the CP-22LP has a removable reservoir.

Buying a condensing water heater? See our gas tankless water heater picks and heat pump vs tankless comparison.

FAQ

Do I need a condensate pump for a tankless water heater?

A condensing heater needs the drainage arrangement specified by its maker. Rheem’s RTGH manual describes gravity drainage and recommends an external neutralizer for acidic condensate. That manual does not establish a condensate-pump installation, and the pump documents reviewed here do not name water heaters. If gravity drainage is impossible, ask the heater maker for an approved design and exact pump requirements. An acidic or high-temperature rating alone does not establish compatibility.

Why does a condensate pump need an overflow switch?

A failed pump or blocked discharge can let water escape. A correctly connected and tested high-water switch can trigger the intended shutdown or alarm; a disconnected switch cannot. Little Giant says its overflow switch can be wired to shut down the furnace or AC, or to run a separately bought alarm. DiversiTech builds an overflow switch into both pumps here. Wire it to low voltage only: Little Giant calls for a Class II low-voltage circuit, and DiversiTech for the appliance’s 24 V shut-down circuit.

How high can a condensate pump lift water?

Check the curve, not just the maximum. Little Giant lists 80 GPH at 1 foot, 48 at 10 feet and zero at its 20 foot shut-off, and its manual says to run the discharge up no more than 75 percent of the pump’s total head. DiversiTech lists 22 feet maximum lift for both models. Neither headline is a usable-flow guarantee at that height. Check the actual flow curve and route; FP-22’s published flow figures conflict and need clarification.

How do I keep a condensate pump from failing?

Clean it. Little Giant’s manual says to unplug the pump, check that the floats move freely, wash the tank with warm water and mild soap, backwash the check valve, and flush the tank with fresh water so acidic condensate does not pit it. It also says to inspect and test the system every 6 months. DiversiTech’s instructions say to clear slime and debris out of blocked outlet tubing and to clean the tank with soap and warm water only, not solvent cleaners.

Where should a condensate pump discharge?

To a proper drain. Little Giant says to run the tubing straight up, slope it down slightly at the top, and, if possible, route it to a drain below or about level with the bottom of the pump, which sets up a siphon. Plumber’s note: local code decides what counts as a proper drain for condensate, so check before you tie in, and do not dump it beside the foundation.

Why Trust Plumbing Picks

Plumbing Picks is written by a licensed Georgia journeyman plumber. Every spec here comes from the maker documents linked below, or from the Amazon listings we link; nothing comes from hands-on testing. The selected linked offers were sold by Amazon.com and in stock when checked on October 8, 2026. Offers and package contents can change; confirm before buying. If you buy through a link we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.

Sources

Which Pump Fits Your Setup?

Compare the VCMA-20ULS for its stated equipment applications and 140°F limit, adding the discharge tubing omitted from model 554425. Consider the FP-22 for acidic furnace condensate only after clarifying its temperature and flow conflicts. Choose the CP-22LP for approved AC/dehumidifier work when its actual clearances fit. For a water heater, obtain the heater maker’s approved drainage design first. Have the overflow circuit tested and keep the tank and discharge path clean.