How Do You Stop Condensation on Water Pipes?

Updated: May 28, 2024

Whether you call it pipe condensation or sweating pipes, it's a bigger problem than you might think. Here our experts explain what to do about it.

As far as plumbing problems are concerned, pipe condensation may seem like a minor one, but that’s actually not so. I consulted several plumbers about this, and all agreed with Asif Bux, who owns a plumbing and HVAC service in Calgary, Alberta. He listed four negative results of leaving the problem unaddressed: mold, structural damage, pipe corrosion and reduced energy efficiency in HVAC systems. None of these are minor issues.

Some folks refer to condensation as sweating, which creates confusion for plumbers who use that term to refer to soldering copper pipes. But you get the idea. Water condensing on the outside of pipes makes it look like they are sweating, and while this usually happens to cold water pipes, HVAC expert Keith Wortsmith wants you to know it can also happen to hot water pipes. Ahead, learn why pipes sweat and what you can do to prevent it.

What Causes Condensation on Cold Water Pipes?

Condensation forms on a surface because there’s moisture in the air and a temperature differential at the surface.

I grew up in a house with single-pane windows, and on cold winter days, water droplets formed on the windows and sometimes even turned to ice. This happened because cold air in the vicinity of the window couldn’t hold as much moisture as the warmer air in the rest of the house, and some of it precipitated out.

The same thing happens at the surface of a cold water pipe. The amount of condensation increases as the temperature differential between the pipe and the room increases — you get more condensation on a cold pipe in a very warm room than you do on a cold pipe in a cold room. Condensation also increases with increasing room humidity.

What’s the Difference Between Condensation and ‘Sweating’ Pipes?

As long as you aren’t talking about soldering copper pipes, there’s no difference between pipe condensation and sweating pipes. As moisture condenses onto a metal pipe, it forms small droplets that gradually become bigger ones and eventually begin dripping. It can look like the water is coming from inside the pipe and that it is sweating, but it isn’t. The water is coming from the surrounding air.

That’s assuming, of course, that the pipe isn’t leaking.

How to Tell the Difference Between Condensation and a Leaky Pipe

Very old copper pipes in a habitually humid environment can corrode and develop pinhole leaks, says mitigation specialist Bethany Uribe, and when water starts seeping through these holes, then you can truly say that the pipe is sweating. Because the holes are small, water doesn’t spray, but forms droplets on the pipe that closely resemble condensation. You can tell the difference because the droplets are localized rather than covering the entire pipe, and they actively drip.

Water can also seep from screw joints that aren’t tight enough and solder joints that have been weakened by pipe vibrations and movements. Even though water may run along the pipe for some distance before it begins dripping, I have found that pinpointing a leaky joint is usually fairly easy. Repairing it, on the other hand, isn’t always so easy: You usually have to drain the water, disassemble the joint and re-do it.

Risks of Pipe Condensation

Every expert I interviewed, including those I don’t mention here, agreed on the four main risks of pipe condensation mentioned by Bux:

  • Mold: Condensation provides an ideal environment for mold and mildew growth, which can lead to health issues like respiratory problems and allergies.
  • Structural damage: Persistent condensation can lead to water damage in walls, floors, and ceilings, potentially compromising structural integrity.
  • Pipe corrosion: Over time, condensation can lead to the corrosion of metal pipes, increasing the risk of leaks and bursts.
  • Reduced energy efficiency: Condensation can reduce the efficiency of HVAC systems, leading to higher energy bills.

In addition, Uribe warns that condensation can promote freezing and bursting pipes in sub-zero environments. This happens because of the cooling effect of evaporation, which makes the pipes colder than they would otherwise be. Wortsmith adds that condensation is a warning of another problem in your home: poor ventilation.

How To Prevent Condensation on Cold Water Pipes

Again, I found consensus among experts regarding ways to prevent condensation.

  • Insulate the pipes: Insulation acts as a barrier, preventing warm, humid air from making contact with the cooler surface of the pipes, thereby eliminating the primary cause of condensation.
  • Improve ventilation: “Install exhaust fans or promote natural airflow,” says Bux. “This helps disperse humid air and prevent moisture build-up, reducing the chance of condensation.”
  • Reduce humidity: Deploy dehumidifiers in problem areas. Bux maintains that keeping indoor humidity levels below 60% significantly reduces the likelihood of condensation forming on pipes.

A long-term solution suggested by Wortsmith is to replace metal water pipes with plastic ones. “Plastic pipes are less prone to condensation than metal pipes, as they do not conduct heat as well. Installing plastic pipes (PVC for cold water, CPVC for hot water, and PEX for both cold and hot water) can help prevent condensation issues.”

Do Hot Water Pipes Sweat?

Pipe condensation isn’t as common for hot water pipes as it is for cold water ones, but it does happen in high-humidity environments, says Wortsmith. “Moist air comes into contact with the hot surface of the pipes, which may be cooled slightly by the surrounding air, and the moisture in the air condenses on the surface of the pipe.”

Wortsmith cautions that HVAC pipes are also at risk: “Pipes that carry refrigerant for air conditioning systems can also form condensation because they are typically colder than the ambient air.” Maintaining the relative humidity below 60 percent generally solves both problems.

What’s the Best Kind of Pipe Insulation to Use to Prevent Condensation?

You don’t have to get fancy; inexpensive foam pipe insulation (about $0.50 per linear foot) usually does the job. I find it super easy to install: simply separate the insulation at the slit, fit it around the pipe and wrap PVC tape around it to hold it in place. Just be sure to buy the right size insulation for the pipes you want to protect.

About the Experts

  • Asif Bux is the owner and service manager of Comfort Union, a full-service plumbing and HVAC company in Calgary, Alberta.. He’s also a licensed gas fitter.
  • Keith Wortsmith is president of DASH Heating, Cooling and Plumbing based in Central Arkansas. The company is family owned and has been in operation since 1931.
  • Bethany Uribe is an AHERA certified building inspector and a damage mitigation consultant affiliated with ASAP Restoration based in Phoenix, AZ.