Furnace Humidifier Cleaning in Toronto and the GTA

Furnace humidifier cleaning clears the mineral scale, slime and dust that build up in the humidifier mounted on your furnace ductwork, so it adds clean moisture to dry winter air instead of a musty smell. Comfort Clean cleans the housing, the water tray, the pad frame and the bypass duct, and tells you when the pad needs replacing.

It is one of the additional services you can add to a furnace and duct cleaning visit, priced by quote. We have been family run since 1980, and we clean: repairs, plumbing and wiring on a humidifier go to a licensed HVAC technician.

How a furnace humidifier works: bypass, fan-powered and steam

A furnace humidifier, also called a whole-house humidifier, is mounted on the supply or return ductwork beside the furnace. A small water line feeds it, a humidistat on the wall or the duct tells it when to run, and the furnace blower carries the moisture through the house.

There are three common types in GTA homes:

• Bypass: the most common. A round duct connects the warm supply side to the return, and some of the warm air passes through a wetted pad and picks up moisture. The bypass duct has a damper with a summer and a winter position.
• Fan-powered: the same kind of pad, but with its own small fan blowing warm air through it, so there is no bypass duct. It usually sits on the supply plenum and puts out more moisture than a bypass unit.
• Steam: an electric unit that boils water in a canister or cylinder and sends the steam into the duct. It delivers the most moisture and does not depend on warm furnace air.

Older houses sometimes still have a drum humidifier: a rotating foam belt that dips into a tray of standing water. Drum units are the hardest to keep clean, because the water sits still between cycles.

Mineral scale, slime and mould on pads and trays

Every litre of water a humidifier evaporates leaves its minerals behind. Tap water across the GTA carries enough calcium and other minerals to turn a soft pad into a stiff, crusty slab over a heating season, and to coat the distribution tray, the water outlet and the drain with white scale.

Scale is more than a looks problem. A crusted pad cannot soak up water evenly, so the humidifier puts out less moisture, more water runs straight to the drain, and blocked outlets can send water where it should not go.

Moisture plus dust is also what mould needs. Any humidifier that holds standing water, or a pad that stays damp in a warm, dark duct, can grow slime and mould. The usual suspects:

• Drum humidifiers, where the reservoir sits full between cycles
• Units left on, with the water running, into the summer
• Pads that are years past their replacement date
• A clogged drain line, so water sits in the bottom of the housing
• A humidistat set so high that water condenses inside the ducts

When a humidifier leaks into the plenum or the supply duct for months, rust and mould can spread into the ductwork itself. That is a moisture problem first. The leak has to be fixed before cleaning and air duct sanitizing of the affected ducts makes sense.

Signs your humidifier needs cleaning

Most homeowners never look at the humidifier until something smells or drips. These are the signs we hear about most:

• A musty or swampy smell at the start of the heating season, strongest near the furnace or from the vents
• White crust on the pad, the tray or the outside of the housing
• A pad that feels stiff like cardboard or crumbles when you touch it
• Rust streaks or water stains on the plenum or the duct below the humidifier
• Dry air, static shocks and cracked lips even though the humidifier is switched on
• Water dripping, pooling on top of the furnace or running nonstop to the floor drain

Some of these point past cleaning. A pad that never gets wet may mean a stuck solenoid valve or a closed water line, and water that never stops can mean a valve that will not shut. Those are parts, and they go to a licensed HVAC technician or a plumber. We will tell you, with photos, what we see.

Winter dryness in the GTA and getting the setting right

Cold winter air holds very little moisture. Once it is heated to room temperature inside your house, its relative humidity drops sharply, which is why January in Toronto brings static shocks, dry skin, scratchy throats and gaps opening in hardwood floors. A working furnace humidifier puts some of that moisture back.

Too much is a problem as well. Moisture the house cannot hold ends up as condensation on the coldest surfaces: windows, the corners of outside walls, the attic. Streaming windows and dark spots in window corners are the signs to turn it down.

Most humidifier manuals and humidistats include a chart that lowers the setting as the outdoor temperature drops. Follow it, and turn the setting down further during a deep cold snap.

Homes with an air exchanger need both settings checked together, since the HRV removes moisture while the humidifier adds it. Our air exchanger and HRV cleaning page covers the HRV side.

What we clean on a furnace humidifier

We clean furnace humidifiers on the same visit as your furnace and ducts, with the same truck-mounted negative-pressure vacuum and brushing. On a typical bypass or fan-powered unit we:

• Shut off the water and the power to the humidifier before we open it
• Remove the pad and its frame, and photograph their condition
• Clean the scale off the distribution tray, the water outlet and the pad frame
• Clean out the housing and the bottom of the cabinet, and check the drain connection
• Clean the bypass duct and its damper, or the fan on a fan-powered unit
• Reassemble, turn the water back on and check that water reaches the pad and drains away
• Take before-and-after photos

On a drum humidifier we empty and clean the reservoir and the drum, and remove the scale and slime. On a steam humidifier we clean the housing and the area around it; whether the canister can be cleaned or has to be replaced depends on the model, and we tell you which.

We do not install, repair or replace humidifiers or their parts. Water valves, solenoids, wiring, humidistats and water lines are work for a licensed HVAC technician or plumber, and so is a new humidifier. When something is leaking or looks unsafe, we point it out and photograph it so you can show your technician.

The furnace side of the visit is explained on our furnace cleaning page.

When a humidifier pad or filter should be replaced

The pad, also called the humidifier filter, water panel or evaporator pad, is the part that wears out. Most manufacturers call for a new one at least once a heating season, and sooner where scale builds fast. A pad cannot be cleaned back to new: once the minerals harden inside it, it stops soaking up water evenly.

When we clean the humidifier, we tell you whether the pad can stay for now or needs replacing, and show you the photos. We do not sell parts. The model number is printed on the humidifier housing or on the old pad, and matching pads are sold at hardware and HVAC supply stores. Many homeowners swap it themselves, since it usually slides in and out of a frame.

A pad is done when:

• It is stiff, crusty or heavy with white scale
• It has dark, green or black patches, or smells musty
• It is torn, collapsed or crumbling
• Water runs over it in channels instead of soaking through
• Nobody in the house remembers when it was last changed

The foam belt on a drum humidifier wears out the same way and is replaced, not washed, once it hardens.

Shutting the humidifier off for summer, and back on in fall

A furnace humidifier has no job in a humid Toronto summer, and leaving it on is how trays and pads end up growing slime. At the end of the heating season, usually when you switch the system over to cooling:

• Turn the humidistat to off
• Close the water supply valve to the humidifier
• On a bypass humidifier, set the damper to its summer (closed) position, so cooled air is not sent back around through the bypass
• Take out the pad and let the housing dry out
• Empty and dry the reservoir on a drum unit

In the fall, before the heating season:

• Put in a fresh pad if it is due
• Open the damper to the winter position and turn the water back on
• Set the humidistat for the season and watch the windows over the first cold weeks

Late summer and early fall are also the best time to have the humidifier cleaned with the furnace and ducts, so the whole system starts the winter clean.

Humidifier cleaning with your furnace and ducts, and pricing

A humidifier sits right on the furnace ductwork, so cleaning it on the same visit as the ducts and the furnace makes sense. A scaled, slimy humidifier keeps putting a musty smell into freshly cleaned ducts, and a dusty plenum keeps dirtying a freshly cleaned humidifier.

Humidifier cleaning is an additional service, priced by quote. It is not part of any air duct cleaning package, and the price depends on the type of humidifier, its condition and how it is mounted. Tell us the type and roughly how old it is when you call, and we confirm the total by phone before we book.

Our posted duct cleaning packages are:

• Basic, $329, up to 10 vents: the supply side, from the furnace supply connection through the supply lines and supply main.
• Comfort, $399, up to 10 vents: the supply and return sides, plus the J-channel.
• Luxury, $499, up to 15 vents: the furnace blower compartment cleaned and the ductwork sanitized with a natural product (Benefect), on top of everything in Comfort.

Every package includes before-and-after photos, extra vents are $12 each, and there is no trip fee inside our service area. The full breakdown is on our duct cleaning prices page.

Our office is at Bathurst and Finch in North York, just south of Steeles, and we clean furnaces, ducts and humidifiers across Toronto and the GTA. Call 905-738-1878, ideally in late summer or early fall, before the heating season fills the calendar.