Every dryer installation guide has a vent length chart: the longest exhaust run the dryer's blower can push air through, shortened for every 90-degree elbow. Past that length, heat and lint stay in the duct instead of leaving the house, and drying times climb.
In San Diego two situations push vents past their limits more than any other. Condo and apartment buildings, especially mid-rise buildings in Downtown, Mission Valley and University City, often route dryer exhaust through long horizontal runs or up to the roof. And garage and interior-closet laundry in tract homes frequently vents across a ceiling to the far wall. Near the coast, a third factor shows up at the end of the run: hood flaps stiffened by salt air.
What the charts say
Whirlpool and LG both treat 4-inch rigid metal duct as the baseline and subtract length for each elbow:
| 90° elbows | Whirlpool 29-inch dryers, box or louvered hood | Whirlpool 29-inch dryers, angled hood | LG, 4-inch wall cap |
|---|---|---|---|
| 0 | 64 ft | 58 ft | 65 ft |
| 1 | 54 ft | 48 ft | 55 ft |
| 2 | 44 ft | 38 ft | 47 ft |
| 3 | 35 ft | 29 ft | 36 ft |
| 4 | 27 ft | 21 ft | 28 ft |
- •Whirlpool (W10617663C): The guide calls for only 4-inch heavy metal vent and clamps, with no plastic or metal foil vent. Flexible metal vent is allowed only where it can be reached for cleaning, with a total length of no more than 7 3/4 feet. The exhaust hood must be at least 12 inches from the ground, and screws or tape that stick into the duct aren't allowed. Long-vent models in the same guide are rated for much longer runs, from 120 feet with no elbows. Whirlpool says longer runs shorten dryer life and reduce drying performance.
- •LG: LG states that the maximum run should not exceed 65 feet, with 6 feet deducted for each additional elbow, and no more than four 90-degree elbows. Its chart, shown above, drops faster than that 6-foot rule, so read the chart line for your elbow count. A smaller 2 1/2-inch wall cap opening cuts the allowance to 55 feet with no elbows. LG says to avoid plastic or vinyl duct.
Older guides differ. An older Whirlpool Corporation gas dryer guide (models RGD4100S and others) also listed flexible metal runs, such as 36 feet with no elbows and a box or louvered hood. Use the guide for your dryer, not a chart for another model.
Why length matters
- •Friction. Every foot of duct and every elbow slows the air. Past the rated length, the blower can't carry the moisture out.
- •Heat. Slow air keeps heat in the drum and duct, so the dryer cycles its heater more and runs longer.
- •Lint. Slow air drops lint in elbows and low spots, which narrows the duct further.
- •The hood. Smaller or angled openings add resistance, which is why the angled-hood column is shorter.
San Diego specifics
- •Condo vent runs. Many condo owners don't know where their dryer vent ends. Some terminate on a balcony wall, others share a roof area with neighbors' vents. If your building's vents are cleaned on an HOA schedule, ask when yours was last done and whether the cleaners reached the termination.
- •Coastal hood caps. In La Jolla, Pacific Beach, Ocean Beach, Coronado and the North County beach towns, salt air corrodes hinges and springs on exterior hood flaps, and lint sticks to the damp marine-layer residue. A flap that no longer swings fully open adds resistance the chart doesn't account for.
- •Tract-home garages. In Mira Mesa, Rancho Bernardo and eastern Chula Vista, dryers sitting in an interior laundry room often vent through a ceiling to the side yard. Those runs pick up elbows quickly, and a hot garage adds its own strain; see washer and dryer garage temperature limits.
- •Rooftop terminations. A vertical run to the roof works against gravity and collects condensation on cool nights, which glues lint in place.
How to check your run
- Find your dryer's guide and the chart for its model and hood type.
- Measure the duct from the back of the dryer to the outside hood, including vertical sections.
- Count every 90-degree turn, including the elbow right behind the dryer.
- Go outside with the dryer running. The flap should open fully and you should feel strong, warm airflow.
- Check any flexible section. It should be metal, short and visible, not foil, vinyl or hidden in a wall.
- Compare your total with the chart line for your elbow count.
What we check on a service visit
- •Exhaust airflow at the hood, and whether the flap opens freely.
- •The transition duct behind the dryer for crushing and lint.
- •The dryer's blower wheel and lint chute, which clog in long-run installations.
- •The thermal fuse and high-limit thermostat, which trip when airflow is poor and are a common reason a dryer stops heating.
If the vent is within spec and loads are still damp, the dryer itself needs a look. See our dryer repair page, or our pages for LG and Whirlpool dryers. Closet installations add their own limits, covered in laundry closet requirements.
Work for other trades
- •Rerouting a vent through framing, a floor or the roof is work for a contractor or dryer-vent specialist. Ask your building department whether a permit is needed, and in a condo, get HOA approval.
- •Moving a gas dryer to shorten the run means disconnecting gas, which is a job for a licensed plumber or gas contractor.
- •Moving a dryer closer to an outside wall may need a new outlet from a licensed electrician.
Frequently asked questions
My condo's vent run is longer than the chart allows. What are my options? Ask the HOA what the building allows. Options include a long-vent dryer model, rerouting with fewer elbows, or a ventless or heat pump dryer that needs no exterior vent.
How often should a long vent be cleaned? There's no single schedule. Long runs, rooftop runs and coastal terminations clog faster, so check the hood flap and airflow every few months and clean when drying times start to stretch.
Sources
- •Whirlpool: 29-inch electric dryer installation instructions W10617663C (vent length chart; 4-inch metal; flexible limit; hood height)
- •LG: Dryer Proper Venting and Installation Tips (65-foot maximum; 6 feet per elbow; four-elbow limit)
- •Whirlpool Corporation: Gas dryer dimension guide 8562589 (older chart with flexible metal runs)
If your dryer takes two cycles and you're not sure whether the vent or the machine is at fault, book a visit online and we'll check both.