Do I need to replace all my rusty pipes?

If they're galvanized and the house is old, you probably do, says Jeanne Huber.

Q I live in a 1940s house that has galvanized pipes. The cold-water tap in the bathtub has become blocked. A plumber said debris from the pipes was clogging the pipe and the only thing I could do was repipe the whole house. Is this my only option?

A There are a couple of other options, but, in the end, the best one is probably what the plumber recommended.

Galvanized pipes, which were used for decades, are made of steel with a coating of zinc, inside and out, to keep the steel from rusting.

But over the decades, minerals in water gradually eat away the zinc and the coating itself wears down from the friction of passing water.

Wherever the zinc wears through, rust can form and build up. Rust takes up more space than steel, so the corrosion eventually fills up the pipe.

“It's a rusty, crusty mess,” said Tim Whistler, owner of Tim Whistler Plumbing & Gas Fitting (timwhistlerplumbing.com), which works in parts of Maryland and Washington.

No piping system lasts forever. Many plumbing websites say galvanized pipes have a life expectancy of 40 to 50 years, while others say 80 to 100. Clearly, the lower range wasn't accurate for the pipes in your house. But at 80 or older, the clock is ticking.

You can find advice online about unclogging galvanized pipes by injecting compressed air to force out debris. But this can just shove the mess farther down the line, where it can collect in plumbing bends or clog up faucets, Whistler said.

It wouldn't fix any rust that has formed at threaded joints. And because the pipes are hidden behind walls, there would be no way to know whether the air pressure had blasted through weak spots where the steel was mostly rusted through — until you switch the water back on, only to discover soggy walls, floors or ceilings.

Some companies have built on the idea of blasting away debris by offering a service that blows out the corrosion with forced air, then sprays in an epoxy lining that protects the remaining steel from further corrosion.

The big advantage is it repairs the corroded pipes without creating the mess it takes to dig up soil or break through walls to switch the piping.

For sewer drain lines and water lines in commercial buildings, which are wider than residential water lines, this process is well-established. For home-size water lines, one concern would be whether the coating reached all the surfaces.

One company that uses the epoxy-lining process is Specialized Pipe Technologies. But it no longer treats residential water lines, just drain lines and commercial water lines.

President Justin Mizell said the pipe diameter of residential water lines is too small to snake a camera through after the epoxy is applied.

“We need to verify, to make sure it's all coated,” he said. “We used to do residential, but two years later, there'd be a leak.” The best solution? “Just repipe,” he said.

The final option, short of replacing all the pipes, is to replace just the section that's clogged. But there is a good chance other sections of pipe also are corroded.

Instead of discovering low flow at another faucet, you might first notice where the remaining old pipe has rusted through and started to leak.

A spokeswoman at Heil Plumbing DMV (heilplumbingdmv. com) said spot repairs often turn out to be short-term fixes, at best. “It's a Band-aid, an expensive Band-aid,” she said.

For a long-term fix, replacing all the pipes is the best option. But it isn't cheap or hassle-free.

Whistler said the cost often ranges between $6,000 and $10,000 for a house with three bathrooms, but that's just for the plumbing work, which includes cutting wall or ceiling surfaces to access the pipes.