Prevent Water Damage with a Float Switch

A PURE member returned home after work to find massive amounts of water throughout his house. The air conditioning unit located in the attic had leaked, ruining hardwood floors throughout the home as well as the custom cabinetry in his recently remodeled kitchen. Damages totaled over $113,000 – costs that may have been avoided had a float switch been in place.

What is a float switch?

An HVAC system produces condensation as it works to cool, dehumidify and heat a home. This excess condensate is usually drained safely away, but naturally-occurring debris like dust and rust can sometimes cause the drain to become slow or clogged, creating leakage. Considering that one HVAC unit can turn as much as 20 gallons of humidity into condensate per day, it is easy to imagine how much damage can occur if that water is not draining properly.

A float switch is an inexpensive device designed to detect when the unit is leaking and prevent significant damage by shutting it off.

Float Switch Functionality

As its name suggests, a float switch is turned on (activated) when the water level in an HVAC's safety drip pan rises past a certain point and the mechanism of the switch begins to float. The switch then sends a signal to the HVAC unit, shutting it off to halt the phase conversion process and stop the production of excess condensation. At that time, the cause of the leak can be repaired before any water damage is able to occur.

Where is a float switch installed?

Horizontal HVAC units are often equipped with a drip pan, which is placed underneath the unit to prevent small amounts of excess condensate water from causing damage. However, in the event of a major leak, a drip pan can only hold so much before it overflows. A float switch installed on the drip pan could prevent such a situation from causing major damage.

For a vertical HVAC unit or horizontal unit without a drip pan, a float switch can be installed on the unit's PVC drain pipe and will activate if water flow is obstructed. An HVAC unit may also come equipped with a condensate pump, which actively pumps excess condensation away from the unit instead of passively relying on gravity to drain it away. Such a pump also includes a float switch-like mechanism which works in the same way, disabling the HVAC unit and preventing the occurrence of major water damage.

 Float Switch Placement

No matter where your HVAC unit is located, it's important to install a float switch or, if appropriate for your unit, a condensate pump. An overflow on the top level of your home could cause significant damage to the floors below and result in microbial growth, mold and hazardous living conditions. However, ground floor unit leaks can easily cause a great deal of damage as well.

What is the cost of a float switch?

Float switches are inexpensive to add to your HVAC system. The part itself typically costs less than $50, and your HVAC professional should be able to install it in under a half hour. Your HVAC professional can also determine whether your unit could benefit from a condensate pump.


PURE members who have questions or need assistance regarding float switches or condensate pumps can contact a PURE Member Advocate® at or 888.813.7873 (PURE).