Pinhole Leaks in Galvanised Pipes: The Silent Killer in Older SA Homes

What galvanised pipe is, and why it fails

Until roughly the early 1980s, almost all hot- and cold-water reticulation in South African homes was done with galvanised mild steel pipe — steel coated inside and out with a thin layer of zinc to slow corrosion. The zinc lasts 40–60 years. Most galvanised plumbing in older SA homes is now well past its expiry date.

Failure doesn't look like a burst. It looks like a pinhole — a 1-2 mm spray that soaks the inside of a kitchen cupboard, the back of a wardrobe, or the wall cavity behind a bath, often for weeks before anyone notices.

Why it's worse in coastal homes

Cape Town, Durban and the Eastern Cape have aggressive water chemistry combined with salty air. The internal zinc layer in coastal homes is typically gone by year 35, and electrolysis at copper-to-galvanised junctions (very common in homes that were "half re-plumbed" in the 1990s) accelerates pitting dramatically.

The warning signs before a pinhole bursts

• Reduced flow at one specific tap (rust scale narrowing the bore).
• Brown or yellow water when a tap is first opened after standing.
• Sudden municipal bill jumps with no obvious leak.
• Tide-line stains on skirting boards or inside built-in cupboards.
• A faint metallic smell from hot water.

What you can't do

You cannot patch one pinhole and walk away. Once one section perforates, the rest of the run is at the same age and the same chemistry — the next leak is months away, in a different spot. Insurance assessors know this and will often decline progressive-deterioration claims on galvanised pipe.

What a good plumber will recommend

• Replace entire runs, not individual sections. Most plumbers re-plumb in PEX (polyethylene cross-linked) or HDPE because it can be threaded through ceilings and walls with minimal damage.
• Leave the old galvanised in place where it's buried in walls — chasing it out is destructive and unnecessary if it's isolated.
• Replace any galvanised geyser inlet tail at the same time. This is the single most common pinhole location.
• Install isolating valves at every fixture so the next leak (in the future) can be contained quickly.

Budgeting expectation (2026)

A full re-plumb of a 3-bedroom freestanding home using PEX runs roughly R28 000 – R55 000 depending on access, geyser relocation, and how much of the old line stays. Get three quotes — pricing in this category varies wildly because labour is most of the cost.