A plumbing roof vent is meant to stay open: the 2024 IRC calls for an open vent at least 6 inches above the roof or snow line, sealed with approved flashing. Many “PVC vent caps” listed online are made for furnace or radon pipes, so check with your inspector before capping a plumbing vent. If the vent leaks, fix the flashing; Oatey’s All-Flash boots and replacement rain collars cover common sizes.
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This guide covers the top of a plumbing vent stack where it passes through the roof.
What the code says about the top of a plumbing vent
The 2024 IRC, Section P3103 (codes-conv.iccsafe.org), covers vent pipes that end outdoors. A roof vent that is not one of the special cases must terminate at least 6 inches above the roof, or 6 inches above the expected snow, whichever is higher.
The code describes these as open vent pipes, and P3103.4 says a vent terminal shall not be used for any purpose other than a vent terminal. P3103.3 requires the joint between the vent pipe and the roof to be made watertight with an approved flashing.
P3103.5 keeps an open vent terminal at least 4 feet below and 10 feet horizontally from doors, openable windows and air intakes unless it is at least 3 feet above them. In very cold climates, P3103.2 requires roof and wall vent extensions to be at least 3 inches in diameter to resist frost closure.
Should you put a cap on a plumbing vent?
In our Amazon search on October 15, 2026, most “PVC vent cap” results were screened termination caps listed for furnace intake and exhaust or radon fans. A plumbing vent has to stay open to let air into the drain system, and anything that narrows the opening can clog with leaves, ice or frost.
Because the IRC describes the termination as an open vent, ask your local inspector before adding any cap or screen to a plumbing vent. Some jurisdictions allow specific designs and some do not.
If animals or debris are the problem, deal with the cause first; if a vent keeps getting blocked, have it inspected rather than capping it shut. A blocked vent shows up as gurgling drains and slow fixtures; our wet venting guide and trap arm guide explain how vents protect trap seals.
Our AAV vs vent guide covers when a mechanical vent can replace a roof vent.
The part that actually leaks: the flashing
When a vent pipe leaks at the roof, check the flashing first. The flashing is the boot with a flat base under the shingles and a rubber collar that seals around the pipe.
Oatey’s roof flashing guide (oatey.com) lists what to match: the roof pitch, the climate (UV, temperature swings and salt air), the vent pipe diameter and the roof type. It warns never to stretch a smaller collar over a larger pipe or to use sealant to fill a collar that is too big.
It also notes that if the flashing base is sound but the rubber collar has cracked, a replacement rain collar can be installed over the old one.
Oatey All-Flash 11919: 1-1/2 to 3-inch vent pipes
Choose the Oatey All-Flash 11919 for a 1-1/2, 2 or 3-inch vent. Oatey’s product page (oatey.com) lists it as a thermoplastic No-Calk roof flashing with an 11-1/4 × 15-inch base for 1-1/2 to 3-inch pipe, and says the patented collar fits multiple pipe sizes in residential and commercial roofs.
On October 15, 2026, the standard new offer from a third-party seller showed stock with model 11919.
Check Oatey All-Flash 11919 roof flashing on Amazon →
Oatey All-Flash 11920: 3 to 4-inch vent pipes
Choose the Oatey All-Flash 11920 for a 3 or 4-inch main stack vent. Oatey’s page lists it with a 12 × 16-inch thermoplastic base for 3 to 4-inch pipe.
On October 15, 2026, the standard new offer from a third-party seller showed stock with model and part 11920.
Check Oatey All-Flash 11920 roof flashing on Amazon →
Oatey 14136: replacement rain collar
Choose the Oatey 14136 when the flashing base is still tight under the shingles but the rubber collar is cracked. The listing describes a multi-size rain collar for No-Calk roof flashings, and Oatey’s guide says such a collar installs over the existing one to restore the seal.
It saves pulling shingles. Replace the whole flashing instead if the base is rusted, cracked or lifting.
On October 15, 2026, the standard new offer sold by Amazon.com showed stock with model and part 14136.
Check Oatey 14136 rain collar on Amazon →
Installing a new flashing
Oatey’s steps for a finished roof: pry up the nails holding the old flashing, lift the shingles above it and slide it off. Chamfer the pipe end, clean the pipe and roof, slide the new flashing down flush against the underlayment and shingles, and nail it where the nails will be hidden under the next rows of shingles.
Shingles above the flashing overlap its top edge; the bottom edge of the base sits on top of the shingles below, so water runs over it.
Oatey suggests testing by running water on the roof above the vent for 15 minutes and then checking the attic where the pipe comes through. Work safely on the roof, or hire a roofer for steep or high roofs.
Frequently asked questions
How high must a plumbing vent stick out of the roof?
Under the 2024 IRC, at least 6 inches above the roof or above the expected snow, whichever is higher, unless a special case applies.
Can I put a cap on my plumbing vent?
The IRC describes roof vents as open terminations. Check with your local inspector before adding any cap or screen, since many caps are made for furnace or radon pipes.
Why is water leaking around my vent pipe?
Usually the flashing’s rubber collar has cracked or the base has lifted. A replacement rain collar can fix a cracked collar if the base is sound.
What size roof flashing do I need?
Match the vent pipe size. Oatey’s All-Flash 11919 fits 1-1/2 to 3-inch pipe and the 11920 fits 3 to 4-inch.
How far must a vent be from a window?
IRC P3103.5 keeps an open vent terminal at least 4 feet below and 10 feet horizontally from openable windows and doors, unless it is at least 3 feet above them.
How we chose
This document-based guide makes no hands-on testing claim. We read Section P3103 of the 2024 IRC, Oatey’s All-Flash product page and Oatey’s roof flashing installation guide. On October 15, 2026, all three linked standard new offers showed stock and matched their model numbers. Read our selection method and about Plumbing Picks.
Primary sources
- 2024 IRC Chapter 31, Section P3103 (codes-conv.iccsafe.org): open vent termination height, flashing, prohibited use, location from openings, frost closure. Model code; local adoption varies.
- Oatey All-Flash No-Calk roof flashings (oatey.com): 11919 and 11920 sizes and bases.
- Oatey: How to Install a Roof Flashing (oatey.com): selection factors, collar sizing warning, rain collar, steps, water test.