Ask him about it, and he’ll probably say that PEX — short for “cross-linked polyethylene” — is better and more affordable than copper. It’s universally accepted by building codes and comes with a 25-year warranty.

But if you Google it, you’ll see numerous blogs and chat rooms questioning whether PEX could leach toxic chemicals into the drinking water that flows through it.

So, is PEX safe? And what are the alternatives for plumbing pipes?

We asked Tristan Roberts, editorial director of “Environmental Building News,” a leading research publication about green building, to help us sort out fact from fiction.

Best for longevity: Copper

Strengths: Copper is unquestionably the premium choice, simply because it has such a long and proven history. Copper piping has been used for 80 years — and many of those original lines are still going strong.

Enviro factor: Copper plumbing pipe won’t pollute your drinking water, and old pipes can be recycled. However, copper mining and manufacturing are so environmentally damaging that despite its longevity and recyclability, copper plumbing pipe is nowhere close to a green product.

Cost:
Copper is a globally traded commodity, and its price has climbed so dramatically in recent years that using it for your project could cost thousands more than it would have just a few years ago. $285 for 100 feet.

Best for tricky retrofits: Cross-linked polyethylene (PEX)

Strengths: PEX can be snaked into walls easily, so it’s great for retrofitting. One piece of PEX can extend across the entire house, curving around corners and obstructions, without any seams. And where a joint is needed, there’s no soldering involved. The pipe — and the joints — have held up well throughout the product’s 30-year history, though PEX wasn’t widely used until about 10 years ago.

Enviro factor:
There’s research linking the process used to make PEX with methyl tertiary butyl ether, a toxin found in gasoline. That leaves some environmentalists worrying that PEX pipes could contaminate the water that runs through them.

But the state of California — known for having the toughest environmental regulations in the country — recently approved PEX for use there.

“That was a big test case,” says Roberts. “And I think it has quieted a lot of the concerns.”

Some industry watchers think that today’s product is safer than the first generation PEX used a couple of decades ago. If you were an early PEX adopter and you’re concerned, run the water for a few minutes to flush out what’s been sitting in the pipes before filling a drinking or cooking vessel.

Cost: $30 for 100 feet.

Best for DIYers: Chlorinated polyvinyl chloride (CPVC)

Strengths: A close cousin to the rigid, white PVC (polyvinyl chloride) that’s the longtime standard for residential waste pipe, the chemical makeup of CPVC contains additional chlorine, which makes it safe for drinking water.

It has a 40-year history of durability, and it’s by far the easiest product for weekend DIY warriors to install because it requires no special tools or skills. You cut the pipe with a handsaw and join it together using the company’s matching fittings and adhesives.

Enviro factor: It’s not a green product because its manufacture is highly polluting. Also, it’s not recyclable, and joining the sections of pipe requires volatile chemical solvents. However, once it’s installed in your plumbing system, there aren’t any bad health consequences for your water quality.

Cost: $50 for 100 feet.

Best for water safety: Polypropylene pipe (PP)

Strengths: It doesn’t get a lot of attention in the U.S., but PP has a 30-year history in Europe, where it enjoys an unblemished record for durability and health safety. It’s a rigid plastic pipe, like CPVC, but it’s not joined together with chemicals. Instead, heat is used to melt the mating ends and fuse them permanently together.

Enviro factor: “If you want to go green, this is the best option,” says Roberts. “There are no safety concerns about chemicals leaching from polypropylene, and there’s no reason the pipes shouldn’t last practically forever. PP is the future of water pipes.”

Cost:
Installing it requires specialty tools that are cost-prohibitive for a small DIY plumbing project, but that aren’t a burdensome investment for a professional plumber who’ll use them again and again. $110 for 100 feet.