A house on a crawlspace has its building drain hanging in the open beneath the floor, where an inspector with a light can see most of it directly. That makes a crawlspace house the easiest to inspect and the cheapest to repair, and it changes how the camera is used: the visual inspection covers the exposed drain and the camera covers the inside of it and everything beyond the foundation wall.
Quick answer: inspect the exposed drain from the crawlspace first, checking hangers, continuous slope, joint condition, staining, material changes and the stack bases, and photographing anything suspect. Then camera the drain from a cleanout to the main for the inside of the pipe and the buried lateral. Pay attention to where the drain passes through the foundation, to any section buried in the crawlspace floor, and to crawlspace moisture that is corroding cast iron from the outside.
Getting into the crawlspace
Access hatches are often small and the space is often wet, low and unpleasant. A buyer should still insist that the inspector enters, or sends a camera on a pole, rather than looking in from the hatch. The drain is the reason.
Hangers and support
Horizontal drain should be supported every four feet or so for plastic and at every joint for cast iron, with no sag between supports. A sag is a belly in the making; a missing hanger with a visible dip is a belly already. Look for improvised supports, wire, scrap wood, which signal past work by someone in a hurry.
Slope
Sight along each run. Drain should fall continuously toward the exit at roughly a quarter inch per foot for 3 and 4 in pipe. A run that goes flat or rises is holding water and solids. A level across a short section confirms it.
Joints and staining
Every joint is a potential leak. Look for mineral staining, rust streaks, dark soil below a joint, and on cast iron, for weeping at the hubs. A leak under a crawlspace may have been running for years into the soil without anyone noticing; the soil below tells the story.
Material changes
A crawlspace drain in an older house is often a patchwork: original cast iron, a PVC repair, a rubber coupling, galvanized branches. Each transition is a joint to check and a clue to past problems. Note where cast iron remains, because that is where the camera needs to look hardest. Cast iron vs PVC on camera explains what each shows inside.
Stack bases
Where each vertical stack turns into the horizontal drain is the wettest joint in the house and, on cast iron, the first to rust through. Look at the base of each stack for rust scale, weeping and soft metal. A stack base that is failing is a repair now, not later.
Where the drain exits
The building drain passes through or under the foundation wall to become the lateral. Look at that point for a sound sleeve, for soil movement, for a sag where the drain leaves its last hanger and enters the ground. Everything beyond is the camera’s.
Buried sections
Some crawlspace drains dip below the crawlspace floor for part of their run. Those sections are not visible and are inspected only by camera; note where they begin and end so the footage can be matched.
Crawlspace moisture
A wet crawlspace corrodes cast iron from the outside, rots hangers and invites roots under the foundation. Standing water, efflorescence on the walls and a musty smell are drainage findings that affect the pipe. Note them.
What the camera adds
The inside of the cast iron, which can look sound outside and be channeled within. The buried sections and the lateral to the main. The condition of the joints from inside. The route and depth beyond the foundation, with the sonde. Camera from a crawlspace cleanout, which is usually easy to reach, to the main. Interpreting the footage covers reading it.
Repairs are cheap here
A crawlspace drain is replaced with hand tools in a day; the same drain under a slab is a week and a floor. Buyers of crawlspace houses should price findings accordingly and should not walk away from a house over a drain they can see and reach.
What to record
Photographs of each run with defects marked, the material map, the stack base condition, the exit point, the moisture conditions and the camera footage to the main with distances. See what a report should include.
Encapsulated crawlspaces
A crawlspace that has been encapsulated, with a sealed vapour barrier over the floor and up the walls, is drier and better for the house, but the barrier hides the soil below the drain. Staining and wet soil under a leaking joint, the clearest sign of a slow drain leak, are no longer visible, and a leak can run under the plastic for years. In an encapsulated crawlspace the inspector should look harder at the joints themselves, at any bulging or discolouration of the barrier beneath them, and should rely more on the camera to confirm the inside of the pipe. Ask when the encapsulation was done and whether the drain was inspected first; a barrier laid over an already-leaking drain has sealed in a problem.
Common questions
Do I need a camera inspection if the drain is visible in the crawlspace?
Yes, for the inside of the pipe and for the lateral beyond the foundation, which is not visible from anywhere.
What is the most common crawlspace drain finding?
Sagging unsupported runs and rusting cast iron stack bases.
Is a wet crawlspace a sewer problem?
It is a drainage problem that becomes a sewer problem by corroding cast iron and rotting supports. Fix the water first.
Related guides
See slab foundation homes, manufactured home drain inspection, and cameras for old houses.