How do I size a condensate pump?

Measure how high the water has to rise from the pump to the highest point of the tubing. Little Giant says that rise should be no more than 75% of the pump's shut-off height. So the VCMA-15ULS (15 ft shut-off) covers rises up to 11.25 ft and the VCMA-20ULS (20 ft) up to 15 ft. Flow rarely matters for a home furnace or AC: the pump moves far more than the system makes.

Does a condensate pump need a safety switch?

For a furnace, yes. The ICP and Weather King furnace guides say the pump must have a safety switch that turns the furnace off if the pump fails. The switch is wired into the low-voltage thermostat circuit (the R wire) so it cuts that circuit when the tank is full. If you have not wired a thermostat before, have an HVAC tech do it. On Little Giant VCMA pumps, the switch comes only on names with S after UL, such as the VCMA-15ULS. Check your local code too.

Is furnace condensate acidic?

Yes. A national lab measured pH 3.4 to 3.8 from a 92% efficient gas furnace. Little Giant's VCMA pumps say they are suitable for condensing furnaces, and its manual says to flush the tank so the water does not get more acidic than about pH 3.4. If a pump is not made for acidic water, furnace makers say to put a neutralizer ahead of it.

How much water does a furnace make?

At most about 1 gallon an hour for every 100,000 Btu of input, while it runs. That is the limit set by burning natural gas or propane; real furnaces make less. An 80,000 Btu furnace makes at most about 0.8 gallons an hour.

Can I use a regular condensate pump for a mini split?

Usually not. A mini split head drips into its own small pan up on the wall, so it needs a small pump made for mini splits, often hidden in the line cover. Check that the pump is rated for your head's Btu size and has a shut-off switch. The Little Giant EC-1-DV, for example, is rated to 34,000 Btu but has no safety switch.

Do condensate pumps get recalled?

We found no CPSC recall of any condensate pump from 1990 to October 2026.

Which Condensate Pump Do You Need?

Pick a condensate pump by how high it has to push the water, not by gallons per hour. Even the smallest tank pump here moves 25 gallons an hour at 10 feet up, about 31 times what an 80,000 Btu furnace can make. For a furnace, get one with an overflow safety switch that is rated for furnace water, which is acidic.^[2]^[4]^[3]

We earn a commission if you buy through our Amazon links. It never changes the price or our picks.

By Erin Rose · Updated October 17, 2026

01 / The three rules

What decides the pump

First, do you need one? If a floor drain, sink drain or sump sits lower than where the furnace drains, the water can run there on its own. Furnace makers call for a pump when there is no floor drain, or when local code requires one.^[3]
Height, not flow. A pump's flow drops as it pushes water higher, and stops at its shut-off height. Little Giant says to keep the rise to 75% of that height or less.^[1] Every tank pump here still moves far more water than a home furnace, AC or dehumidifier makes, so the rise decides the model. Mini split pumps are much smaller; see below.
An overflow safety switch. If the pump fails, the switch turns the furnace or AC off before the tank overflows. The installation guides for ICP and Weather King furnaces say the pump must have one.^[3] On Little Giant VCMA pumps, only names with S after UL have it: ULS, or ULST, which adds tubing.^[2]
Acid, for furnaces. Furnace water is acidic: a national lab measured pH 3.4 to 3.8.^[7] Use a pump made for furnace water, or add a neutralizer ahead of it if your furnace maker or local code calls for one.^[3]

02 / What to buy

The pumps, and how much they move at each height

Each tank pump has an overflow switch, a maker spec sheet with flow at each height, and a maker statement that it suits condensing furnaces. Flow is from that sheet, in gallons per hour.^[2]

For a rise up to 11.25 ft

Little Giant VCMA-15ULS

Overflow switch, rated for furnace water, shuts off at 15 ft. Flow: 65 gal/hr at 1 ft, 50 gal/hr at 5 ft, 25 gal/hr at 10 ft.

$57.63 at Amazon, checked October 17, 2026

Check price on Amazon

For a rise up to 15 ft

Little Giant VCMA-20ULS

Overflow switch, rated for furnace water, shuts off at 20 ft. Flow: 80 gal/hr at 1 ft, 70 gal/hr at 5 ft, 48 gal/hr at 10 ft.

$63.70 at Amazon, checked October 17, 2026

Check price on Amazon

For a rise up to 18 ft

Little Giant VCL-24ULS

Overflow switch, rated for furnace water, shuts off at 24 ft. Flow: 270 gal/hr at 1 ft, 260 gal/hr at 3 ft, 250 gal/hr at 5 ft, 210 gal/hr at 9 ft.

$169.92 at Amazon, checked October 17, 2026

Check price on Amazon

For a mini split head

Sauermann Si-30 (120 V)

Rated for units up to 67,000 Btu, with a safety switch and UL/CSA listing. Up to 5 gal/hr; at a 33 ft rise it still pushes 1 gal/hr. Quiet: 20 dBA. A very large head with a very tall rise is a job for the installer.^[8]

$164.38 at Amazon, checked October 17, 2026 · sold by Test Equipment Depot

Check price on Amazon

Watch the name on the Little Giant furnace pumps: the VCMA-15UL ($57.60 at Amazon on October 17, 2026) looks the same, but it has no overflow switch. On Little Giant VCMA pumps, the switch comes only on names with S after UL: ULS, or ULST, which adds tubing.^[2]

Add-ons

RectorSeal Safe-T-Switch overflow switch

Adds a shut-off switch to a drain line or pump that lacks one.

$12.49 at Amazon, checked October 17, 2026

Check price on Amazon

American Valve CondensateRx neutralizer

Goes ahead of the pump when local code or your furnace maker calls for neutralizing the acid.

$55.00 at Amazon, checked October 17, 2026

Check price on Amazon

03 / Questions

Frequently asked

How do I size a condensate pump?: Measure how high the water has to rise from the pump to the highest point of the tubing. Little Giant says that rise should be no more than 75% of the pump's shut-off height. So the VCMA-15ULS (15 ft shut-off) covers rises up to 11.25 ft and the VCMA-20ULS (20 ft) up to 15 ft. Flow rarely matters for a home furnace or AC: the pump moves far more than the system makes. ^[1]^[2]
Does a condensate pump need a safety switch?: For a furnace, yes. The ICP and Weather King furnace guides say the pump must have a safety switch that turns the furnace off if the pump fails. The switch is wired into the low-voltage thermostat circuit (the R wire) so it cuts that circuit when the tank is full. If you have not wired a thermostat before, have an HVAC tech do it. On Little Giant VCMA pumps, the switch comes only on names with S after UL, such as the VCMA-15ULS. Check your local code too. ^[3]^[2]
Is furnace condensate acidic?: Yes. A national lab measured pH 3.4 to 3.8 from a 92% efficient gas furnace. Little Giant's VCMA pumps say they are suitable for condensing furnaces, and its manual says to flush the tank so the water does not get more acidic than about pH 3.4. If a pump is not made for acidic water, furnace makers say to put a neutralizer ahead of it. ^[7]^[1]^[3]
How much water does a furnace make?: At most about 1 gallon an hour for every 100,000 Btu of input, while it runs. That is the limit set by burning natural gas or propane; real furnaces make less. An 80,000 Btu furnace makes at most about 0.8 gallons an hour. ^[4]
Can I use a regular condensate pump for a mini split?: Usually not. A mini split head drips into its own small pan up on the wall, so it needs a small pump made for mini splits, often hidden in the line cover. Check that the pump is rated for your head's Btu size and has a shut-off switch. The Little Giant EC-1-DV, for example, is rated to 34,000 Btu but has no safety switch. ^[8]^[9]
Do condensate pumps get recalled?: We found no CPSC recall of any condensate pump from 1990 to October 2026. ^[10]

04 / Sources

Where this comes from

1
Little Giant VCMA series owner's manual
Read October 17, 2026. Route outlet tubing straight up, "not exceeding 75% of total dynamic head capacity of the pump." In a gas furnace setting, keep the condensate from falling below "the average pH of 3.4" by routinely cleaning or flushing the tank. The overflow switch "will open (break) a low voltage electrical circuit ... This can be used to stop the condensing unit(s)".
2
Little Giant spec sheets: VCMA-15, VCMA-20, VCL-24
Read October 17, 2026. Gallons per hour at 1/5/10/20 ft: VCMA-15ULS 65/50/25/0 (shut-off 15 ft); VCMA-20ULS 80/70/48/0 (shut-off 20 ft). VCL-24ULS 270/260/250/210 at 1/3/5/9 ft (shut-off 24 ft). Overflow switch only on models with S after UL in the name (ULS, and ULST, which adds tubing); UL and ULT have none. "suitable for high efficiency oil and gas-fired condensing furnace and condensing boiler equipment."
3
ICP and Weather King condensing furnace installation instructions (Carrier family)
Read October 17, 2026. "A condensate or sump pump MUST be used if local codes require, or if no inside floor drain is available". "A condensate pump MUST have an auxiliary safety switch to prevent operation of furnace and resulting overflow of condensate in the event of pump failure. The safety switch MUST be wired through the R circuit ONLY (low voltage)". "A condensate neutralizer cartridge MUST be installed in the drain line unless pump is approved for use with acidic condensate." The Weather King manual (gemaire.com) says the same.
4
Weil-McLain Technical Bulletin SB-1201 (March 30, 2012): condensate production from condensing appliances
Read October 17, 2026. "For every 1,000 BTU's of input = 0.01gallons of condensate can be produced in 1 hour of continuous operation." The most that burning natural gas or propane can make; real units make less. (A boiler maker, but the limit comes from the gas itself, so it bounds a gas furnace too.)
5
Condensate collection manual (University of Arizona WRRC, 2013), citing San Antonio Water System
Read October 17, 2026. For large commercial buildings in a San Antonio summer: "0.1 to 0.3 gallons per hour (gph) of water per ton of cooling." The extreme-case figure, 0.031 gallons per minute per ton, "is not expected to be a sustained condensate flow rate." No maker publishes a figure for home AC, so we use this commercial rule as a rough guide.
6
ENERGY STAR dehumidifier specification v5.0 (final draft): capacity definition
Read October 17, 2026. Capacity is "measured in pints collected per 24 hours of operation". 8 pints = 1 gallon.
7
Oak Ridge National Laboratory (Energy, 2022): condensate from a 92% AFUE gas furnace
Read October 17, 2026. "The measured pH value varied within the range of 3.42-3.76". One 80,000 Btu furnace.
8
Sauermann product catalog: Si-30 mini-split pump
Read October 17, 2026. "suitable for air-conditioning units up to 5.6 tons (67k Btu/h)". Max flow 5.0 gph; max discharge 33 ft at 1 gph; 20 dBA; safety switch; UL/CSA certified by Intertek; 120 V model.
9
Little Giant EC-1-DV mini-split pump spec page
Read October 17, 2026. For mini splits "up to 34,000 BTU"; no safety switch in the maker's table.
10
U.S. CPSC recalls database, 1990 to October 2026
Searched October 17, 2026 for condensate pumps and the brands on this page: no condensate pump recalls.
11
Amazon.com listings (price and seller from the product page)
Prices checked October 17, 2026. Prices change; the button shows today's.