Podcast Q&A: Blue Stains After Water Softener Installation

Note: This podcast transcript has been edited for clarity and length.

Hi, my name is Gerry Bulfin. I’m a WQA-certified master Water Specialist and water contractor here in Santa Cruz, California, Northern California. I go deeper into various well water treatment systems and problems each week on our main podcast, but I’m trying to do more of these quick Q&A episodes. We get so many questions daily, and people email, call, and chat with us through our website, so there are always great questions.

This week, John contacted us and said, “We recently had a water softener installed, and now we’re having a problem with blue stains. The company that installed the softener tested our water, and it is not acidic. They said it was not their fault and that they could not help. Have you ever heard of this happening?”

What Causes Blue Stains in Homes With Copper Pipes?

Well, John, yes, we have done it quite a few times. Let me talk about where the blue stains come from. You probably already know this, but blue staining inside, like the blue stains you see on your fixtures, bathtub, or laundry, is a result of copper corrosion. So your house, no doubt, has copper pipes. If you see blue stains, something is corroding the copper pipe. Most of our customers who have problems with blue stains have acidic well water.

So that’s a good reason to check the water and make sure it’s not acidic. If the water is acidic, usually, we find that corrosive water that is acidic is not that hard. Therefore, it’s aggressive water, and you have a problem with copper corrosion, and you get blue stains. The answer is to fix the acidity using our calcite neutralizer, fresh marble, or calcium carbonate.

When It’s Not the Water: Plumbing Problems That Cause Corrosion

You had a water softener installed because your water is hard, and the installer confirmed it’s not acidic. So why the blue stains? In many cases, the issue comes down to plumbing.

Often, the ends of copper pipes aren’t properly deburred before installation. This leaves jagged edges that become corrosion sites. In some cases, too much acid flux is used during soldering, which can also lead to internal corrosion—especially if not cleaned off properly.

The only real fix is to find the affected section of copper pipe, remove it, and have it replaced—ideally by a plumber who carefully deburrs and installs it correctly. If it’s a short section, you might be able to switch to stainless steel flex lines instead.

Here in the Bay Area, we’ve seen widespread issues with copper corrosion due to poor plumbing practices combined with naturally corrosive water. Local agencies have even issued alerts urging better installation practices to avoid this kind of problem.

Is the Softener Itself Causing the Staining?

Another myth that folks often think about is softeners. They think they remove the calcium carbonate and hardness, so now the softener makes the water aggressive or corrosive. In fact, that’s not true. If you have hard water and a neutral pH, meaning it’s not acidic, softening the water is not going to make the water aggressive or corrosive. That’s my experience of what we know.

Protect Your Pipes: Calcite Acid Neutralizer

If your water softener has stopped blue-green staining but copper corrosion persists, it could be a sign of acidic water. Our Calcite Acid Neutralizer gently raises pH using natural calcium carbonate, protecting plumbing from corrosion and blue stains without harsh chemicals or complex maintenance. Available in multiple sizes, it’s a perfect complement to your water treatment setup.

What You Can Do About It

Anyway, I hope that’s helpful. It’s bad news, but I don’t want to get in the middle of it with your contractor plumber. That’s what I will suggest. You can tell him that it wasn’t there before they did the softener, but now they’ve done it. You got the blue stains, and yeah, it’s a problem. It’s most likely the piping and the way it was done. It could be inferior piping in very rare circumstances, but I haven’t run into that myself. I’ve heard of it, but there are other problems with the jagged ends, such as not deburring, not preparing the copper pipe properly, and/or using too much flux, which can cause the problem.

Okay, well, if you have a question, please contact us through our website, cleanwaterstore.com. There’s a little chat box on there, where you can ask a question, or you can just do it the old-fashioned way: give us a call. We’re happy to talk to you about any kind of water issue, problem, or question you might have. Thanks again for listening.