Understanding Condensate

Over my 21-year career of inspecting homes, condensate is one of the most frequently reported items in my inspection reports. I find it’s done wrong more than 75% of the time in one fashion or another. I am convinced it’s because people don’t consider condensate to be something that can lead to a larger issue—and that could not be farther from the truth.

Condensate is no different than any other water-carrying pipe. The many creative ways in which homeowners or contractors incorrectly deal with condensate are a never-ending source of inspection defects. I imagine it’s also a never-ending source of insurance claims. Let’s look at what is required. I will provide the requirements without stating the code,
as codes may vary by location, year, municipality, etc.

The plumbing requirements for condensation discharge are as follows.

• Condensate drains shall not directly connect to any plumbing drain, waste, or vent pipe.
• Condensate drains shall not discharge into a plumbing fixture other than a floor sink, floor drain, trench drain, hub drain, standpipe, utility sink or laundry sink, or approved trap.
• All HVAC equipment that produces condensate must have either a secondary drain line or a condensate overflow switch, a secondary drain pan with a secondary drain line, a condensate switch, or some combination of these installations should be used to prevent overflow if the primary drain line blocks.
• Condensate from cooling coils and evaporators shall be conveyed from the drain pan outlet to an approved place of disposal. Such piping shall maintain a minimum horizontal slope in the direction of discharge of not less than one-eighth unit vertical in 12 units horizontal (1% slope).
• The inside diameter of the condensate drain
  shall be no smaller than three-fourths inches and shall be no smaller than the drain pan outlet. Three-fourths is sufficient up to 20 tons.
• The condensate drain shall discharge to a conspicuous location.
• The condensate drain shall be designed to allow
  for cleaning without cutting the drain.

Now, this is just the basics. There are more requirements for specific applications, however
the above requirements cover most of the issues
a home inspector may encounter.

Let’s look at some common defects.

Trapping Issues. Traps are required on most
applications of condensate drains. Dehumidifiers
are one of the most common sources of incorrect drains tapped directly into a domestic sewer line.
The intention is to avoid having to empty the collection container, so drain hoses have been incorrectly
tapped directly into a main sewage line. This creates
a sanitary hazard and a leak potential. Any opening
into the domestic sewer line must be trapped to
prevent sewer gas release into the home. There also must be an air gap to prevent cross contamination.

Pitch and Support. Condensate drains must be
properly sloped and supported to allow for proper drainage. This is another area where lack of support allows the drain line to hold water and potentially clog or even freeze in the winter. Condensate drains are flexible, and if not supported the line can sag and potentially become disconnected from the disposal source and create a leak issue.

Freeze Protection. Condensate disposal systems must be protected from freezing. This is critical in cold climates. Heating systems, AC units, and condensing water heaters must have a condensate disposal system that is protected from freezing, and this prevents
disposal out of the home where the discharge point
is exposed to cold temperatures. The line will freeze, the condensate will back up, and damage will occur.

HVAC units installed in the attic that are of condensing heat design are required to have R-2 min insulation protection. Most quality HVAC contractors who work in cold climates install heat tape and pipe insulation on the condensate line.

Condensate drains do have to be cleaned regularly. The design must allow for cleaning without having to cut and splice the line. If you have to cut the line
to clean it, it’s wrong.

Blockages in Condensate Drains. There are many different reasons why a condensate line was blocked.

• Lack of cleaning at the regular service interval.
• Insects in the condensate line. Bees and other insects are attracted to the condensate line
  due to its size and the presence of moisture.
• Poor slope. Standing water can grow bacteria
  and mold that can block the drain.
• Insulation. Blown-in cellulose attic insulation is often unintentionally sprayed into an attic condensate drain pan by contractors.
  The contractor then fails to clean the pan.
  This cellulose blocks the drain.
• Rodents. Small rodents have been known
  to get into the condensate drain and get stuck.
• Rust and debris inside the coil can accumulate
  and block the drain.
• Capped drain vents. Trapping and venting of condensate lines that are incorrectly installed
  can prevent condensate from draining properly.

Now let’s look at some examples of what a proper condensate drain should look like.

A. This clear condensate trap for an HVAC is an ideal trap with a unique design for inspecting and cleaning the trap. It comes with a brush to allow cleaning.
The caps open to clear the drain from the pan into
the drain. Notice the open vent on the drain side
of the line. This allows proper drainage. If that vent were capped, it would cause a vacuum and restrict proper drainage.

B. This is a proper waste receptacle installed on a main domestic sewer line. The drain has a proper trap with a large opening to allow an air gap. Notice the plug just below where the condensate line was previously installed directly into the sewer line. I had inspected this home and called out the improper means of condensate disposal. The homeowner had the system repaired, and I went back to confirm the proper repair.

Now let’s look at some examples of incorrectly installed condensate drains.

C. This attic HVAC condensate line is directly tapped into the sewer vent in the attic. This is not allowed. Sewer gasses will enter the HVAC through the condensate line, which has no trap or air gap.

D. This dehumidifier resting on a chair is directly inserted into the sewer line after the drain, rather than in the trap. Since the trap is not used, the water dried up, and sewer gasses were entering the home.

E. Another condensate line directly entering the sewer line without a trap or air gap. This one is prone to raw sewage discharge into the condensate line.

F. This HVAC trap is doing nothing. The pre-molded plastic trap is installed so steep there is no trap.
There is also no air gap.

G. This condensate drain on the attic HVAC is an
example of a trap that cannot be cleaned without cutting the drain. This is prohibited.

H. This is one of the worst condensate disposal methods for attic HVAC units. The contractor drills a hole through the fascia into the gutter. The standing
water in the gutter will freeze and prevent discharge
of condensate from a heating unit. This can result
in a shutdown of the heating unit.

Now let’s address corrosive condensate.

Acidic condensate is a byproduct of high-efficiency furnaces that use natural gas or propane to produce heat. The heating process results in acidic condensate that poses two potential problems for septic systems. The first problem is that the acidic nature of the condensate could negatively impact the beneficial bacteria in the system. The bacteria in septic tanks and advanced treatment systems prefer a PH between the ranges of 6.5 to 7.5. A high efficiency furnace condensate ranges between 3.0 and 5.0 with some found as low as 2.0. This level of corrosive ability can also damage concrete septic tanks. As a septic contractor I have observed a direct link to septic systems not working well and acidic condensate being discharged
to a septic system with no acid neutralizer in use.

How does corrosive condensate affect household plumbing?

Cast Iron. Cast iron has good corrosion resistance to neutral and alkaline liquids (High PH), but its resistance to acids is poor. When the PH is 4.0 or lower the protective oxides tend to dissolve and corrosion rates increase.

Copper. Copper corrodes with the presence of any PH under 7.0. Well water with a PH lower than 7.0 can corrode copper so imagine what acidic condensate with a PH of 4.0-5.0 can do.

Galvanized Pipe. Galvanized pipe performs well with
a PH range between 5.5 and 12.0.

PVC is the preferred drainage system for any low
PH or acidic condensate.

Condensate from condensing boilers and water heaters must be addressed before being sent into the sewer or septic system. (Code 701.5 Damage to drainage system or public sewer) Wastes detrimental to the public sewer system or detrimental to the functioning of the individual private sewerage disposal system shall be treated and disposed of in accordance with Section 1003 as directed by the code official and in accordance with the authority having jurisdiction.

I. This is a photo of a condensing boiler with a condensate acid neutralizer installed. This setup is perfect. There are several ways to address corrosive condensate. There are in-line and gravity cartridges.

This is a condensate neutralizer cartridge for in line and gravity treatment of corrosive condensate. Lime pellets are inserted into the cartridge. These pellets need to be replaced periodically. The BTU rating determines the frequency where the media needs replacement.

This is a condensate pump with an acid neutralizer in the base. This would replace the traditional condensate pump. These pellets need to be replaced periodically. The BTU rating determines the frequency where the media needs replacement.

When is acid neutralizing required?

If the domestic sewer lines in the home are metallic
in any part of the downstream sewer, an acid neutralizer is required. If you read any manufacturers’ recommendations in the owner’s manual of the condensing appliance you will find condensate disposal requirements.

The following information relates to how corrosive condensate can affect the sewer lines.

Condensing boilers and water heaters can produce as much as half-gallon of corrosive condensation per hour of operation. If you have a condensing boiler and no other water is being used, that boiler or furnace can produce as much as 8 gallons per day of corrosive condensate which can be sent directly into a septic tank. This amount of acid can severely harm a septic bacteria level and impact the function of the septic system to work properly.

When I observe incorrect condensate disposal I refer a plumber for evaluation and repair.

In situations where sewer gasses are entering the home, I report this as a sanitary hazard and potential health hazard. Sewer gases contain hydrogen sulfide (H2S), ammonia (NH4), and methane (CH4). Often, homes with sewer gas issues also have reported people in the home with unexplained illnesses.

Exposure to sewer gasses can cause symptoms of:

• Tiredness
• Irritated eyes
• Coughing
• Nausea
• Shortness of breath
• Headaches
• Irritability
• Memory issues

Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable. Even low levels of H2S can be deadly.

Methane gas is a toxic gas and an explosion hazard. Methane needs a very low energy source for ignition.

Ammonia is an eye and skin irritant and can cause explosions in high levels.

Inspectors entering confined spaces where sewer lines or condensate lines exist are advised to wear
PPE for safety. You may enter the space and discover an issue and by that time you were exposed to
harmful gases.

Photo A courtesy of freedomhvacal.com; Photos B-I courtesy of Advantage Home Inspections.

Opinions or statements of authors are solely their own and do not necessarily represent the opinions or positions of ASHI, its agents, or editors. Always check with your local governmental agency and independently verify for accuracy, completeness, and reliability.