Why Is My Dryer Taking Longer to Dry Clothes?

How a dryer actually dries

Inside the cabinet, a blower pulls room air across a heater (an electric element or a gas burner), through the tumbling clothes and out through the lint screen into the exhaust duct. The water in the fabric leaves as vapor riding on that air stream. Drying speed depends less on how hot the heater gets than on how fast the moist air is carried away and replaced with dry air.

When the duct is restricted, two things happen. Humid air lingers in the drum, so the clothes have nothing dry to give their water to. And the heat has nowhere to go, so the cycling thermostat switches the heater off more often to protect the machine. The dryer keeps tumbling, but much of that time it is barely heating. That is why a clogged vent shows up as a cycle that drags on rather than one that stops working outright.

A quick airflow test you can do

Start with the lint screen. Clean it, then hold it under the tap. If water beads up and sits on the mesh instead of running through, a film from dryer sheets or fabric softener has sealed it, and it needs a scrub with warm soapy water and a soft brush.

Next, run the dryer empty on a heat setting for a few minutes and go to the outside hood, if it is at ground level and you can reach it without a ladder. A healthy vent pushes out a strong, warm stream that holds the flap wide open. A faint puff, a flap that only flutters, or lint hanging from the louvers points to a restriction somewhere between the machine and the exit.

Finally, slide the dryer out a few inches and look at the hose behind it. Note what it is made of and whether it is flattened against the wall or kinked into a tight bend.

Common causes, most likely first

In the older houses we work in, the causes stack up in a fairly predictable order. Most slow dryers are fixed by one of the first three, and a long-neglected vent often has two or three at once.

• Lint packed in the duct, heaviest at elbows, joints and low points
• A transition hose crushed behind the machine or kinked where it meets the wall
• A hood flap stuck with lint or paint, or a screen or nest blocking the outlet
• A run that is too long or has too many turns for the dryer's rated limit
• Duct joints inside a ceiling that have pulled apart, dumping air and lint into the cavity
• Clothes leaving the washer wetter than they should, from a weak spin
• A fault inside the dryer: heater, gas valve coils, thermostat or moisture sensor

Vent problem or dryer problem?

The symptoms usually separate the two. If the air at the hood is strong and warm, the vent is doing its job and the fault is more likely inside the machine. If the air is weak, start with the vent before paying for appliance parts.

Timing helps too. A vent clogs gradually, so drying times creep up over weeks or months. A part inside the dryer tends to fail from one load to the next: yesterday the clothes were dry, today they come out warm and wet, or cold and wet. A dryer that gives no heat at all, on a strong air stream, points inside the machine rather than to the vent.

Why towels and heavy loads lag

Thick cotton towels, jeans and bedding hold far more water than a load of shirts, so they take longer even on a perfect vent. What matters is a change. Towels that used to finish in one cycle and now need two are telling you airflow has dropped.

Sensor dry cycles add a twist. Metal bars inside the drum read how wet the clothes are by touching them. Light items dry first and brush the bars more often, so the dryer can decide the load is done while a heavy towel tumbling in the middle is still damp. Separating heavy and light items, and wiping the sensor bars now and then with a little rubbing alcohol, keeps the reading honest. A washer that no longer spins out properly will also hand the dryer a wetter load than it was designed for.

Why older homes see this more

Brownstones, rowhouses and twins often have the laundry in the basement or in the middle of an upper floor, far from any outside wall. The duct may run the length of the basement along the joists to an exit under the front stoop, or climb two or three floors to the roof. Every foot and every turn gives lint another place to settle.

Renovations add their own problems. Ducts get boxed into dropped ceilings, joints get fastened with screws that poke inside and snag lint, and older vinyl or foil hoses survive behind new appliances. In winter, a duct running through a cold attic or along an outside wall cools the exhaust, moisture condenses, and damp lint sticks harder than dry lint.

When to stop using the dryer

A slow dryer is also a hot one. Lint is fine, dry and flammable, and a restricted vent holds heat right where that lint collects. Stop running loads and get the vent looked at if you notice any of the following.

A gas dryer adds one more concern: its exhaust carries combustion gases, including carbon monoxide. A blocked vent can push those gases back into the house. Carbon monoxide alarms are the safeguard here. If one goes off, head outdoors right away and ring 911 or the utility from there.

• The top or sides of the cabinet are much hotter than usual
• A scorched or burning smell during a cycle
• The dryer stops mid-cycle on its own
• Lint appearing around the door or on the floor behind the machine

What a vent cleaning visit covers

The dryer is pulled out and disconnected, and the transition hose is checked for crushing and for material. Plastic and thin foil hoses are swapped for metal. The full run is then cleaned from the dryer to the exit with rotary brushes and air, the hood is cleared so the flap swings freely, and the airflow at the outlet is checked again with the dryer running. You get a plain account of what was found: crushed sections, loose joints, a hood that traps lint or a run longer than the dryer's manual allows.

If the airflow is strong afterward and the clothes still come out wet, the problem is inside the appliance, and an appliance technician is the right call. When you book, tell us where the dryer sits and where the vent comes out, and we will give you a written price before the work starts.