Why do pipes sweat?


On sweltering days, you may notice that some of your pipes are sweating. This is quite a common issue, and as a result, it’s often ignored as considered fairly normal. It may not sound like a big deal, but sweating pipes are a cause for concern that you should attend to as soon as  possible. Before you find a solution, you might want to know what causes pipes to sweat in the first place.

Why do pipes sweat? Pipes do not literally sweat, although it may appear that way. What is termed “sweat” is condensation that occurs when moisture from the air forms on the outside of a cold pipe or component. When the warm, humid air comes in contact with a chilled pipe or component, it loses its capacity to hold water vapor. As a result, the excess water forms into droplets that can be seen on or near the cold pipe surface.

Metal cold water pipes, including galvanized steel and copper, account for the most significant condensation, although it’s not uncommon to observe it on plastic piping as well. In addition to being annoying, pipe sweating may eventually lead to more serious issues like damaged ceilings, damaged floors, mold growth, and building rot. Condensation is not just an issue during summertime – you can also deal with sweaty pipes during the winter months.

Why does condensation occur on pipes?

Sweating often occurs during the summertime. As cold water comes out of a pipe, it causes the pipe to conduct it’s cold energy. The warm, humid air makes contact with the cold pipe walls through the process of convection and as a result, condensation starts to form on the pipe surface.

In technical terms, condensation on pipes is all about the dew point. This is the temperature that air needs to be cooled to for it to release water vapor. Dew point changes with the amount of water vapor in the air. The higher the humidity levels, the higher the dew point. 

Condensation typically occurs once the temperature has been lowered the dew point. When air cools on contact with the chilled surface of the pipes, it releases the water vapor in the form of those droplets. Condensation is more pronounced on pipes during the summer because the season is more humid and therefore has a higher dew point than other times of the year. That said, the condensation process can also affect piping during the winter as furnaces heat the air.

What are the risks and dangers of condensation?

Condensation may be less of a concern than leaking pipes, but it’s still a concern that needs to be addressed sooner rather than later. Condensation on your water pipes can cause a number of issues, including:

1. It can create a safety hazard

It’s not uncommon to find condensation that forms on pipes leaving a water trail or even puddles on the floor especially if you don’t dry it in good time. This could cause a serious safety hazard for you because a slip or fall hazard is created. You may find yourself sustaining injuries from slipping on a puddle of water that has accumulated on the floor below a pipe. 

2. It can make pipes susceptible to rust and corrosion

Pipes that sweat can pose a serious condensation risk to the integrity of your plumbing system. The risk is elevated when moisture comes into contact with your pipes, particularly if they are made of iron, steel, or any other metal.

Rot is most commonly associated with steel or iron. It occurs due to the oxidation of the surface of the pipe upon exposure to air and water. The thickness of your metallic pipe can be slowly reduced by corrosion leading to holes and eventual structural failure. 

3. It can cause damage to the property

Accumulation of a substantial amount of water on floors and inside cabinets may damage building materials such as subflooring and tile by leaving unsightly stains or even impacting the structural integrity of the property. 

4. Moisture leads to the growth of mold and mildew

Moisture accumulation can lead to the growth of mold especially if the condensation appears in a dark, humid location like basements or attics, which is where a lot of domestic water pipes can be found. Similarly, mildew may also grow on sweaty pipes and can very quickly get out of hand. 

Exposure to mold and mildew can cause a variety of health effects. If you’re sensitive to mold, you may experience symptoms such as a stuffy nose, itchy eyes and/or skin, and wheezing. Some individuals, such as those with asthma or allergies to molds, may experience even more intense reactions which may include shortness of breath and fever. Indoor exposure to mold has also been linked to respiratory tract symptoms in otherwise healthy individuals.

5. It can cause foul odors

Because condensation can encourage the growth of mold and mildew, it can also cause foul odors which can make your space undesirable. 

6. Condensation can encourage the presence of bacteria 

Condensation can turn your pipes into a breeding ground for all kinds of bacteria. As a result, even minor cracks in your plumbing system can pose a contamination risk to the water circulating in your home.

7. Condensation may make it difficult to diagnose leaks in pipes

If the condensation on your pipes is particularly high, it may be hard to tell if you have a leak to deal with or just excessive sweating. To check for leaks, turn off all the water faucets and water-reliant appliances in your home. Check your water meter and note down the number. Wait for about an hour, then check the water meter. If the gauge or number on the water meter has changed, it may mean that your home has a leak. Unfortunately, there’s no way to pinpoint exactly where the leak is coming from, so the sweating or leaking pipe you suspect may not be the culprit. Either way, consider calling in a plumber to fix the issue.  

How can you reduce or eliminate sweating water pipes?

1. Identify the sweating water pipes

The first step to dealing with sweating pipes is to locate them. You may notice a trail of water leading you to the pipes or a puddle of water accumulating under them. Pipes that are most likely to sweat are those that are exposed to the warmer indoor temperatures in your basement or other areas of the house. If you don’t have direct access to the affected pipes, you may need to cut through drywall to solve the problem.

2. Add insulation to cold pipes 

One of the most effective ways to keep your pipes from sweating is to cover them with pipe insulation which will prevent warm, humid air from reaching the cooler surface. Some insulation materials that will work well include:

  • Polyurethane foam pipe insulation – This type of insulation typically comes in 4-6 foot lengths to fit different sizes of pipes . The center of the foam pipe insulation is slit to allow for easy installation. 
  • Fiberglass pipe wrap – This insulation option comes with a polyethylene vapor barrier attached to the back of it. The wrap is laid on top of the affected pipe, and then wrapped and taped so that it stays in place. Because fiberglass can absorb water, you may want to add plastic elbows to your pipes to create a complete pipe insulation system.
  • Polyurethane spray foam pipe wrap – With this wrap, a plastic shell is first laid on top of the pipe, and then the polyurethane foam is either sprayed or poured into the shell so that it completely encapsulates the pipe.

3. Increase the water temperature

Consider raising the water temperature to reduce the occurrence of condensation. This may be effective in making the surface of the pipe slightly warmer than the dew point so that no condensation occurs.

4. Install a ventilation fan 

The humidity that is brought about your long steamy showers doesn’t help the issue; it only serves to increase the dew point. It may be a good idea to install a ventilation fan in moisture-prone areas of your home such as the bathroom and kitchen. With less moisture in the air, there is less that can accumulate on the cool surface of your pipes. 

5. Turn on your air conditioning system

Air conditioners can have the dehumidifying effect that you need to deal with the issue. This is a viable solution as long as the sweating pipe is located somewhere in the temperature controlled portions of your home. 

6. Invest in a whole-house dehumidifier

In summer, your air conditioner efficiently gets rid of a majority of the humidity in your home as it cools the air, but if you live in an especially humid area, you may still have to deal with condensation on pipes. A whole-house dehumidifier effectively reduces the amount of moisture in the air, subsequently lowering the relative humidity of the home. 

7. Install an energy recovery ventilator (ERV)

Sometimes humidity can filter into your living space from damp basements or crawl spaces. In such cases, you might want to consider integrating an ERV into your home’s duct system, which will not only get rid of excess heat and moisture in the air, but, in exchange, will also bring in fresh, drier air.

Final thoughts

Sweating pipes are a common sight in the summer, but this doesn’t mean that it’s a normal occurrence. If no action is taken, you may have to deal with issues such as water damage to your property, the growth of mold and mildew, and foul odors, to mention a few. 

Melanie Asiba

Melanie is an author. She enjoys traveling, reading and trying out new things. In addition to writing for Apartment ABC. Connect with her at [email protected]

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