Tree Roots in Old Clay Sewer Pipes: Why Your Drain Keeps Blocking

Why this is so common in older SA suburbs

Homes built before roughly 1985 in suburbs like Parkview, Berea, Bryanston, Walmer, Berea (Durban), Rondebosch and Newlands were plumbed with salt-glazed clay sewer pipes joined with mortar collars. Over decades the mortar softens, the joints develop hairline gaps, and the moist, nutrient-rich pipe interior becomes the most attractive thing in your garden — for roots.

Plane trees, jacarandas, oaks, syringas and especially fig trees are notorious for invading these joints.

How it actually blocks

Roots enter as fine hairs through a joint gap, then thicken inside the pipe into a dense mat. The mat catches toilet paper, wet wipes, kitchen fats and hair, and the drain blocks. You call someone with a drain machine, they ream out the blockage, water flows again — and within months you're back to the same point because the roots are still there.

The signs it's roots, not just a blockage

• Same drain blocks 2–4 times a year, always in the same spot.
• Gurgling from the lowest gully when you flush an upstairs toilet.
• A patch of unusually green, lush grass over the sewer line.
• Mature trees (over 10 years) within 6 m of the run.
• Slightly sunken paving or a small depression above the line.

What actually fixes it (in order of cost)

1. Mechanical root cutting — a drain machine with a root-cutting head. Cheapest, but buys you 6–18 months at most.
2. High-pressure hydro-jetting with a root nozzle — cleans the joint properly. Lasts longer, but doesn't stop regrowth.
3. CCTV drain inspection — non-negotiable before any permanent fix. The camera shows exactly where the roots enter, how bad the joints are, and whether the pipe has collapsed.
4. Patch lining or full pipe relining (CIPP) — a resin-soaked liner cured inside the existing pipe. No digging, no garden destruction, and roots cannot re-enter.
5. Open excavation and replacement with uPVC — the old solution. Cheap per metre but expensive once you add re-paving, re-lawning and the wall the contractor may have to break.

A warning about chemical "root killers"

Copper sulphate and similar products sold at hardware stores will kill the visible roots inside the pipe — but the dead root mat still has to physically come out, and the chemical is harsh on municipal sewer biology. Some municipalities prohibit it. Don't make it your first move.

What to ask the plumber

• "Do you have a sewer camera?" If not, find someone who does.
• "Can you give me the recording or stills of the line?" You need this for insurance and for any relining quote.
• "What's the pipe diameter and material?" Most SA clay lines are 100 mm or 150 mm — relining is straightforward at those sizes.