What It Means If You See Green Residue in Your Sink

Did you know that the Statue of Liberty and the green residue in your sink have something in common? They’re both the result of a chemical reaction. However, the charming and iconic color on the Statue of Liberty is a lot less exciting when it’s sitting in your sink.

There’s no need to panic; this stain is nothing of immediate concern. However, it’s important to understand what it is and where it’s coming from. This way you can clean it properly and figure out what’s causing it in your pipes. You’ll be able to determine the necessary fix right away instead of spending a lot of money on troubleshooting.

We spoke to a master plumber and a water expert to get you concise answers about this stain and ensure that you’re capable of cleaning it and discerning the cause.

What Is That Green Residue In Sinks?

That green stain in your sink is actually copper deposited from pipes or fixtures. You’ve likely seen it pool around your drain, but the issue isn’t with your sink or drain. It begins inside the pipes before you even turn on the water.

The green residue results from a chemical reaction between the copper deposits caused by corrosion and oxygen, forming copper hydroxide carbonate. Oxidation is why the Statue of Liberty, which is made of copper, has turned green over time.

What Causes Green Residue In Sinks?

The copper stain is caused by the effect of corrosion or a slow disintegration within the home’s plumbing. Here are a few reasons why pipes corrode:

Stagnant water

If copper water pipes have water sitting inside them for long periods, the inside of the pipes can start to corrode.

Water pressure

If the water pressure is too high, the sheer velocity of the water can cause wear and tear over time, leading to corrosion. Maximum pressure in a home should not exceed 80 psi (pound-force per square inch).

Water pH

If the water has an unusually low pH (low alkalinity; less than 6.5) or an unusually high pH (greater than 8.5), pipes are more likely to corrode. Master plumber Bret Hepola of All City Plumbing in Minnetrista, Minnesota says, “Water pH is the primary culprit of the blue-green sink stain.”

Installation error

If air is getting into the pipes or the connections from fittings joining the pipes have not been properly installed, corrosion can occur. Over time, these imperfect scenarios cause the copper in your pipes to break down.

When you turn on the water, these small deposits from the pipes run out through your faucet and into your sink. While they can tint the water green, they are not always visible to the naked eye. However, they are noticeable when they form a blue-green ring in the sink.

How to Remove the Green Residue

Michael Dean, a water expert and co-founder of Pool Research, suggests mixing vinegar and baking soda. “Create a paste, [then] apply it to the stained area and wait at least 10 minutes before wiping/scrubbing it off,” he says.

If the stain is too stubborn, Dean suggests trying a stronger acid than vinegar. However, he says, stronger chemicals may damage the surface of the sink.

Some other common solutions include:

• Salt
• Dish detergent
• Lemon juice
• Cream of tartar
• Ammonia
• Toilet cleaners containing sodium bisulfate

How to Stop the Corrosion

While these solutions leave your sink clean and stain-free, they won’t fix the root cause. Another green stain will likely form in the sink over time. And eventually, if left untreated, this corrosion can cause failures in the plumbing pipes. Depending on the cause, there are a few steps you can take to prevent further corrosion:

Test the water

Checking your water’s pH level is a good place to start. A plumber can test your water for you, but there are plenty of DIY options, including at-home tests. If you want to test for more than pH, complete water testing kits can also detect lead, bacteria, iron, fluoride and copper.

If you find that your pH level is off, an acid-neutralizing filter can be installed. “The correction of pH is often approached by the installation of an acid-neutralizing filter,” Dean says. “However, there are pros and cons to these systems, and depending on the pH level of your water it may or may not be worthwhile going in this direction.”

Patch the pipe

If you find pinhole leaks in your pipes or suspect one may be forming, the easiest and quickest fix is a piece of rubber from a garden hose or similar and a couple of hose clamps. Other options include:

• Water pipe epoxy
• Water pipe tape
• Pipe patch kit

These repairs are only temporary fixes until a pro makes a proper pipe repair. A pro will also diagnose and offer solutions to fix the cause of the leaks.

About the Experts

• Bret Hepola is a Master plumber with All City Plumbing in Minnetrista, Minnesota..
• Michael Dean is a water expert and co-founder of Pool Research