Dryer Vent Length Limits: Building Code vs. LG, Samsung and Whirlpool Manuals
Sources checked: October 21, 2026. This guide summarizes the building-code text and manufacturer documents linked at the end. CodeFix Home is independent of all appliance brands, and this guide has not been reviewed by a licensed installer, code official or appliance technician.
Quick answer
The model residential code (section M1502, as adopted in many US jurisdictions) sets a default maximum of 35 feet of 4-inch metal exhaust duct, with deductions for each fitting. But the same section lets the dryer manufacturer’s installation instructions set the maximum, and those limits can be longer or shorter — LG’s venting table, for example, allows up to 65 feet of straight 4-inch rigid duct with a 4-inch wall cap. Your local code and your model’s manual decide; generic online calculators usually apply only the 35-foot code rule.
Important: this page explains the rules; it is not an installation approval. Duct work inside walls, ceilings or roofs, and any gas dryer installation, should be done by a qualified installer and may require a permit and inspection where you live. Safety disclaimer
Building code vs. manufacturer: the key difference
| Rule source | What it says |
|---|---|
| Residential code M1502 (example: Seattle Residential Code 2018) | Default maximum of 35 ft from the dryer’s transition connection to the outlet terminal, with fitting deductions (e.g., 5 ft for a 4-inch mitered 90° elbow). The transition duct is not counted. Alternatively, the manufacturer’s installation instructions can set the maximum length. |
| LG (general venting page) | A table by number of 90° elbows and wall-cap size for 4-inch rigid metal duct — from 65 ft (no elbows, 4-inch cap) down to 22 ft (four elbows, 2½-inch cap). |
| Samsung (per model; example DVE45T3400W manual) | Its own table for 0–3 elbows with 4-inch and 2.5-inch columns, noted for short runs. Check the manual for your exact model. |
| Whirlpool (per model; example gas dryer guide 8562589) | A table by 0–4 elbows that distinguishes rigid from flexible metal duct and box/louvered from angled hoods. Whirlpool’s general long-dry-time page states an equivalent length under 35 ft. |
LG’s published table (4-inch rigid metal duct)
| Number of 90° elbows | With 4″ wall cap | With 2½” wall cap |
|---|---|---|
| 0 | 65 ft | 55 ft |
| 1 | 55 ft | 47 ft |
| 2 | 47 ft | 41 ft |
| 3 | 36 ft | 30 ft |
| 4 | 28 ft | 22 ft |
Source: LG US, “Dryer proper venting and installation tips” (page dated Nov 14, 2023). The same page also says to deduct 6 ft per elbow, which does not match the table above; we report both and recommend following your model’s installation manual.
Other code requirements worth knowing
- Exhaust duct must be metal, at least No. 28 gage, 4 inches in diameter, with a smooth interior.
- Screws or fasteners must not protrude more than 1/8 inch into the duct, because they catch lint.
- If the duct is longer than 35 ft (allowed under manufacturer instructions), a label stating the length must be placed within 6 ft of the duct connection.
- The flexible transition duct between dryer and wall must be listed to UL 2158A, no longer than 8 ft, and not concealed inside walls or ceilings.
- Plastic and vinyl ducts are not acceptable — LG says never to use them, and Whirlpool advises against plastic or foil accordion ducts.
How to apply this to your home
- Find your dryer’s model number and look up its installation instructions.
- Count the 90° turns between the dryer connection and the outside, and note the outside hood type.
- Measure the straight length of duct (a duct cleaner can do this if it’s hidden in walls — LG recommends asking for it).
- Compare with your manual’s table and check your local code with the building department.
- If you’re over the limit, the run needs to be shortened or rerouted by a professional; a booster fan is a separate topic and should follow manufacturer and code requirements.
Signs your vent run may be too long
Long drying times, a hot laundry room, or blocked-vent warnings (LG d75–d95, Whirlpool AF/Check Vent) that return right after cleaning can all point to a run that is too long or has too many elbows. See blocked-vent codes by brand.
Related guides
Official sources
- Seattle Residential Code 2018, Chapter 15 (section M1502) — example of the model residential code text (checked Oct 21, 2026)
- LG US — Dryer proper venting and installation tips (checked Oct 21, 2026)
- Samsung — DVE45T3400W user manual (PDF) (checked Oct 21, 2026)
- Whirlpool Corporation — gas dryer guide 8562589 (PDF) (checked Oct 21, 2026)
- Whirlpool — Dryer not drying or long dry times (checked Oct 21, 2026)
Codes are adopted and amended locally; confirm with your building department. Featured image: illustration, not a photograph.
