Cast iron
Common in homes built before about 1970, and it fails from the inside out.
Waste is not chemically kind to iron. Over decades the interior corrodes and builds up a rough scale layer, which does two things: it narrows the bore, and it gives passing material something to catch on. So the line starts blocking more often long before it is structurally compromised.
The end state is channelling — the bottom of the pipe corrodes away entirely while the top still looks like pipe. From above, or from a quick camera pass, it can appear serviceable while effectively being a trough.
Typical service life is 50-75 years, so a good deal of Boerne's older housing stock is at or past that point.
The tell is repeat blockages combined with dark, gritty debris in what comes out, and a camera showing a rough, tuberculated interior rather than smooth pipe.
Worth knowing
Snaking a badly corroded cast iron line is a real risk. A cutting head that meets a section already thinned to a shell can go straight through it — which is why a camera before aggressive clearing is not an upsell on a pipe of that age.
Clay tile
Used for sewer laterals for a long time, and it fails completely differently. The clay itself is durable and largely inert — it is the joints that go.
Clay lines were laid in short sections with mortared or gasketed joints. Our expansive soil swells and shrinks through every wet-dry cycle, and over decades that movement pulls those joints apart or offsets them.
Roots then follow the moisture to the openings. They rarely break a sound pipe — they find an existing gap, get in, and expand. Which is why finding roots in what comes out is not really a root problem: it is a joint problem that roots have located for you.
The other characteristic failure is a sag or belly. As soil moves and washes out, a section drops below the intended fall, standing water collects, and solids settle in it. That produces recurring blockages in a pipe that is otherwise entirely intact — and no amount of clearing fixes the geometry.
The other things older houses have
Orangeburg pipe — bituminised wood fibre, used mid-century when other materials were scarce. It deforms into an oval and collapses, and its service life was much shorter than anything else. If you have it, it needs replacing rather than repairing.
Undersized or poorly vented branch lines. Plumbing codes changed considerably. A drain that has always been slow, from day one, may simply be inadequately vented rather than blocked — and it will keep being slow after every clearing.
Improvised alterations. Older houses accumulate work of varying quality. Fittings that create a trap where there should not be one, or a slope that runs the wrong way over a short section, are common and invisible until a camera goes down.
Missing or buried cleanouts. Many older properties have none, or have one paved over during a later project. That raises the cost of every future clearing.
When clearing stops being the answer
The signal is consistent regardless of material: a properly cleared line stays clear.
If a drain blocks again within a few months, the clearing worked and something is causing material to catch in the same place. In an older house that something is usually structural — scale, a separated joint, a sag, or a section that has lost its shape.
At that point a camera costs less than the next two clearings, and it answers the only question that matters: is this a blockage, or is the pipe failing? Those are very different jobs and guessing between them from the symptoms is how people pay for the wrong one.
It also locates the fault, which keeps any excavation small — and on an older property with mature landscaping, that matters.
What the options look like
Spot repair where one section has failed and the rest is sound. Cheapest, and the right answer when the cause was localised rather than age.
Lining is often well suited to older homes: a resin liner cured inside the existing pipe seals separated joints permanently, which is what actually stops roots returning. It needs a host pipe that still holds its shape, so it works on jointed clay and lightly corroded iron but not on a collapse or a badly channelled line.
Pipe bursting replaces the line without trenching the whole route — useful when mature trees, a driveway or established landscaping would otherwise be destroyed.
Full replacement when there is a collapse, multiple severe sags, or Orangeburg. It is the only method that lets the fall be re-established correctly, which matters when sags are the recurring problem.
More detail on choosing between them in repair versus replacement.