Every house has a plumbing vent through the roof, and when there is no cleanout and no toilet that can be pulled, the vent is the way into the drain system. It is also the hardest entry: it involves a roof, a vertical drop through fittings designed for air rather than cameras, and a long way to go before the camera reaches the building drain, let alone the lateral. This guide covers when the vent is the right choice, how to do it safely and what to expect the camera to meet.
Quick answer: use the vent only when a cleanout cannot be found or opened and a toilet cannot be pulled. Work the roof with proper fall protection, a stable ladder and a second person; choose the vent serving the main stack, usually the largest and nearest the bathrooms; feed the rod down slowly, letting gravity take it, and watch for the fittings at each floor and at the base of the stack where it turns into the building drain. Expect the drop and the base turn to use a good share of the rod’s reach, and expect a tight fitting at the base to stop a larger head. A small-head, flexible-rod camera is the right tool.
When to use the vent
After the search for a cleanout has failed, including the exterior walls, the basement, the crawlspace and the garage, and after considering pulling a toilet, which is quicker and safer than a roof and enters the system lower down. The vent is for houses with no cleanout and no accessible toilet, or where the owner refuses a toilet pull. Cleanout access and cleanout vs vent vs toilet cover the comparison.
Roof safety
A roof is where sewer camera work hurts people. Use a ladder rated for the job, footed and tied, and a harness anchored where the pitch or height calls for one. Have a second person on the ground to pass equipment and watch the reel. Do not carry the reel up the ladder; haul it or leave it on the ground and run the rod up. Do not work a wet, icy or steep roof for a camera inspection; find another way or another day. PPE for camera work covers the kit.
Which vent
The main stack vent is usually the largest pipe through the roof, 3 or 4 in, and is above the bathroom group. Smaller vents serve individual fixtures or are branch vents that may not connect to the drain at all without passing through a tee at the top. Choose the largest, and if there is a choice, the one nearest the side of the house where the drain leaves. Remove any cap or screen and check for nests.
The drop
Feed the rod in and let it fall under its own weight for the vertical section, keeping a hand on it so it does not run away and the head does not slam into the first fitting. The picture shows the stack wall passing. At each floor there may be a sanitary tee where a fixture’s vent or drain joins; the head passes straight through most of them going down.
The base of the stack
At the bottom the stack turns ninety degrees into the building drain through a long sweep, a combination fitting or on old houses a sharp bend. This is where the camera is most often stopped. A small head on a flexible rod takes a long sweep; a 23 mm head may take it with rotation and patience; nothing takes a sharp cast iron bend. Bend radius and 90 degree elbows explains the geometry and rotating to steer the technique.
Reach
A two-storey stack uses 20 to 30 ft of rod before the base turn. The building drain under the house uses more. A 100 ft rod entered at the vent may reach the foundation and a little beyond; it will not reach the main on most lots. Set expectations before climbing. Measuring the run applies here as a planning step.
Equipment
A small-head camera on a thin, flexible rod is the tool for vents: it passes the base fitting a larger head will not and its rod follows the vertical and the sweep. A 23 mm head on a 7 mm rod is a gamble at the base. Self-leveling helps read the picture after the rod has rotated in the drop. Small-diameter drain cameras and sewer vs drain camera cover the options.
The counter
Zero the counter at the vent opening and note that distances are from the roof, not from a cleanout, so a finding at 45 ft is 45 ft of pipe including the vertical drop. State the entry in the report. Distance readings covers why this matters.
Retrieval
Pulling the rod back up a vertical stack lifts the head against every fitting from below. Go slowly, rotate at any catch, and have the ground person manage the reel. A head that snags at the base fitting on the way up is freed by pushing down a little and rotating. Retrieving a stuck camera covers the worst case.
Afterwards
Replace any vent cap. Clean the rod, which has been through the whole system. Recommend to the owner that a cleanout be installed, which is a plumbing job of a few hours and makes every future inspection a ground-level one. Cleanout requirements explains why codes want one.
Common questions
Can you put a sewer camera down a roof vent?
Yes, when there is no cleanout and no toilet to pull. It is the hardest entry and reaches the least; a small-head camera on a flexible rod is the right tool.
How far will a camera reach from the roof vent?
The drop and the base turn use 20 to 40 ft of rod. A 100 ft rod typically reaches the foundation and a little beyond, rarely the main.
What stops the camera at the bottom of the stack?
The fitting where the stack turns into the building drain. A long sweep passes a small head; a sharp bend stops most heads.
Related guides
See entering from a cleanout, entering from a floor drain, and pre-purchase inspection.