What Size Sewer Camera Do I Need?
The single specification that can make a camera useless in your pipe — and the one most buyers check last.
Quick answer
Match the camera head diameter to the smallest pipe on the run. As a working rule: 17 mm or smaller for 2 in lines, 23 mm for 3 in and 4 in lines, and 25 mm and up for 6 in and larger where lighting outweighs clearance.
Size for the narrowest point anywhere on the route, not the pipe you are entering. Fittings are tighter than pipe, and a line that reduces mid-run will stop a head sized for the wider section.
Why head diameter is the deciding specification
Cable length, screen size and recording format are all soft constraints. Get them wrong and you have a camera that is less convenient than you hoped.
Head diameter is a hard constraint. Get it wrong and the camera does not enter the pipe. There is no technique, no amount of pushing and no accessory that fixes a head that is physically too large.
This is why we lead every buying guide with it, and why “how long is the cable” is the wrong first question.
How head size maps to pipe size
These are working ranges rather than hard limits — the fittings on your particular run matter as much as the nominal pipe size.
- 17 mm and under — 1.5 in to 2 in lines. Kitchen branches, laundry lines, small commercial fixtures. Also the only realistic option if a P-trap is in the route.
- 23 mm — 3 in and 4 in lines. The standard residential size and what most sewer cameras ship with. Comfortable clearance with enough LED area to light the pipe wall.
- 25 mm and above — 6 in and larger. Found on professional reels. The extra size buys lighting, which you need in a wider pipe, at the cost of small-diameter access.
A 23 mm head in a 2 in line will commonly enter a straight section and then stop dead at the first elbow — which is the worst outcome, because you have paid for a camera and still cannot see the problem.
Size for the narrowest point, not the entry point
Drainage systems change diameter. A 3 in branch may reduce to 2 in before joining the main, and a 4 in lateral may narrow at a repair or a fitting.
Work out the smallest internal diameter anywhere on the intended route and size for that. If you do not know, buy smaller than you think you need — a smaller head in a larger pipe costs you lighting quality, which is recoverable. A larger head in a smaller pipe costs you the inspection entirely.
The trade-off: smaller heads see less
The LED ring scales with the head. A 17 mm head lights a 2 in pipe beautifully because the wall is close. Put the same head in a 6 in line and the wall is beyond the useful throw of the lights, and your footage will be dark and hard to interpret.
This is why small-head reels are specialist tools rather than universally better ones, and why professionals commonly own two systems instead of one compromise.
Head size is not the only access constraint
Head length matters too, particularly at bends. A long thin head can be worse through a tight elbow than a short slightly wider one, because it cannot pivot within the fitting.
Rod flexibility is the other half. A soft rod with a small head clears bends that a stiff rod with the same head will not. See our guide on 90° bends.
A quick way to decide
- Identify the access point — cleanout, removed toilet, or fixture.
- Identify the smallest pipe diameter between there and where you need to reach.
- Choose a head at least a few millimeters under that internal diameter.
- Check whether the route has hard elbows or a P-trap. If so, go smaller and prioritize rod flexibility.
- Only then decide cable length.
Common questions
What is the most common sewer camera head size?
23 mm (about 0.9 in). It is the standard on residential reels because it suits the 3 in and 4 in lines that make up most US household drainage.
Can I use a smaller head in a large pipe?
Yes, but the picture will be dark. The lights are sized to the head, so a small head in a 6 in line leaves the pipe wall beyond their useful range. It works; it just does not document well.
Does head size affect how far I can push?
Indirectly. Small heads are paired with softer rods, and softer rods buckle sooner over distance. So small-head reels tend to be shorter — the head itself is not the limit, the rod that suits it is.