Replacing old galvanised pipes: a homeowner's guide

If your house was built several decades ago and the water pressure has slowly faded, or the first glass from the tap comes out tinged brown, old galvanised pipe could be the reason. This guide explains what galvanised pipe is, why so many older homes in the area still have it, how to tell when it's failing, and what replacing it actually involves. It's written by the licensed plumbers who work on these homes every week from our base in Matraville.

What is galvanised water pipe?

Galvanised pipe is steel pipe coated in a layer of zinc to slow down rusting. For a long stretch of the twentieth century it was a standard choice for carrying drinking water into and around Australian houses. You'll usually recognise it by its dull grey colour and threaded joints, often where the water service comes up beside the house, under the kitchen sink or near the hot water system.

The zinc coating doesn't last forever. Over many years it wears away on the inside, and the bare steel underneath starts to corrode. Rust builds up on the pipe walls, narrowing the bore bit by bit, while the walls themselves thin out. That's why problems with galvanised pipe creep up gradually rather than appearing overnight.

Why older local homes still have it

Many of the post-war brick and fibro houses in Matraville, Maroubra, Malabar and Botany were plumbed during the years when galvanised steel was common. Copper and, later, plastic pipe took over in new homes, but existing houses were rarely repiped unless something went wrong. So it's very common for us to find a property where the bathroom has had newer fittings over the years while the original galvanised pipe still runs under the floor and through the walls.

Often a home has a patchwork: copper in one section, galvanised in another, joined wherever a past repair was done. Those joints between different metals can corrode faster still, which is worth knowing if your plumbing has been fixed piecemeal.

Signs your galvanised pipes are failing

A water bill that climbs for no obvious reason can also point to a leak you can't see. Our hidden water leak guide explains how to check your meter, and we offer leak detection if you need it found.

What replacement involves

Replacing galvanised pipe means running new water lines to take its place. The two materials we generally use are:

• Copper: long-lasting and proven, with soldered or pressed joints. It's a familiar choice for exposed sections and hot water lines.
• PEX (cross-linked polyethylene): a flexible plastic pipe that can be fed through wall cavities and under floors with fewer joints and less disturbance.

Many jobs use a mix of both, depending on where the pipe runs and what's easiest to reach. We start by tracing the existing pipework and working out how much of it is galvanised, then talk you through the options with a fixed price before anything begins.

Repiping doesn't have to happen all at once. A common approach is to do it in stages, starting with the section in the worst condition, such as the main line from the meter to the house, or the lines feeding a bathroom with poor pressure. Raised timber floors make access under the house much easier, which suits a lot of older local homes. We'll explain which sections matter most and help you plan the order.

Why it's worth doing before it leaks

Galvanised pipe tends to fail slowly, then suddenly. A pinhole that's been leaking quietly inside a wall can rot timber, damage plaster and encourage mould. A corroded joint that finally gives way can turn into a burst pipe, with water pouring out until someone turns off the meter. Planning a replacement on your own terms is far less stressful than dealing with water damage, and you'll get better pressure and cleaner water along the way.

Homes near the coast at Maroubra, Malabar and Little Bay can see faster corrosion on any exposed metal pipework, thanks to the salt air. Sandy soil across the area can also shift slightly over time, putting stress on old threaded joints buried underground.

Related help: water pressure guide, hidden water leak guide, leak detection and burst pipe repairs. Local pages: Matraville, Maroubra, Malabar and Botany. Browse all our plumbing guides.