Condensate Drain FAQs for A/C & Heat Pumps

Q&A on HVAC Condensate Drain Installation, Disposal, Leaks, Troubleshooting, Codes

Condensate Drain Pipe or Tube Material FAQs

What type of piping or tubing is used for condensation drainage inside a wall on an inside unit of a split unit?

What type of piping or tubing is used for condensation drainage inside a wall on an inside unit of a split unit? On 2019-08-05 by Bob

Reply by (mod) -

Bob,

In new HVAC condensate drain installation when the drain is run through framed walls, use of a flexible plastic drain line is common - as shown in the photo I'll attach below and as is described further at inspectapedia.com/aircond/Condensate_Drain_Problems.php

However in my OPINION a better installation uses rigid PVC pipe, properly sloped 1/8" to 1/4" per foot. I often find that the flexible condensate drain tubing is not carefully installed nor supported to maintain drainage slope throughout its run.

The result is the accumulation of dust, debris, algae or mold in a dip in the drain that leads to clogging and potentially to a backup and leak of condensate out at the air handler.

In the photo the white flexible condensate drain tubing is being routed down from above where a split system A/C unit is to be hung on the wall.

The drain drops down then runs out through the wall to the building exterior where it drains onto a roof and thence into a gutter and downspout system if not totally evaporated.

The red oval and line mark a critical point where nail plates must be installed to protect the drain line from puncture by future drywall screws or nails.

The black tubing in the photo is actually foam insulated refrigerant piping.

Can you use electrical conduit as a drain condensate pipe ?

Can you use electrical conduit as a drain condensate pipe ? If not could you say why ? Thanks in advance . On 2016-06-09 by Joe

Answer by (mod): NO

Well, no I doubt it. Electical conduit is not designed for nor rated for use as a liquid drain line; also, its connectors are not water tight unless you're using outdoor conduit.

Is plastic condensate drain line piping acceptable?

We had a copper pipe from our natural gas burning ac/heater condensation pump to an appropriate drain.

The pipe deteriorated and leaked in several locations.

The HVAC installer came out and replaced it with clear tubing.

We also have a heat pump that still has a copper drain pipe that the HVAC installer states is fine as it is not from a fuel burning appliance and will not corrode/leak.

Does this sound right? On 2016-09-08 by dave

Answer by (mod): yes

Dave

It sounds believable.

The condensate from a fossil fueled heater is likely to have been acidic and thus corrosive.

But another factor is just what type of copper piping was used for the drain; thin-wall copper piping material may be less reliable.

See LEAK CAUSES in WATER PIPING for more about corroding copper piping.

Illustrated above is Diversitech's 5/8" flexible AC condensate drain tubing - sold at Home Depot and at HVACR suppliers and plumbing suppliers

Outdoor Disposal of Condensate FAQs

What's Code on Outdoor Disposal of A/C Condensate?

Can I route the primary condensate line directly outside? On 2019-05-04 by rlozano9@gmail.com

Answer by (mod) - the proper and an improper AC condensate drain discharge location

RL

Carson Dunlop Associates' sketch shown here illustrates the proper and an improper AC condensate drain discharge location.

Notice that one of the most common condensate disposal locations, connection to a plumbing stack vent pipe, is not recommended and is prohibited by building code in some jurisdictions.

Generally you can route A/C condensate outdoors TO A SUITABLE DESTINATION - that means

- NOT where the water would cause a problem such as splashing up on and rotting siding or attracting insects into a building or draining back into the building thriouugh the foundation

- NOT where the condensate runs across a sidewalk or public spac

How far from the house should an ac drain line be?

How far from the house should an ac drain line be? On 2018-12-11 by Doug Muehl -

Answer by (mod) - code or standard on the clearance distance for releasing AC condensate

I don't think I've seen a code or standard on the clearance distance for releasing AC condensate assuming that you're spilling it directly onto a prohibited area such as a sidewalk.

However it would make sense to be sure that there's no splash back onto a wall surface that causes damage and no source of basement or crawl space water entry. Exact details of what's required to achieve those would be side and building specific.

Can A/C or Heat Pump condensate line drain to the wastelands?

In an industrial installation, can the condensate line drain to the wastelands. Is there a code that says it must drain to sanitary? On 2018-05-11 by Joe

Answer by (mod) - yes but ...

Not sure what you mean by waste lands

Depending on local regulations, HVAC condensate can often be drained into a grassy surface area provided it's not in an area that creates a nuisance.

by Joe

Acres of grassy area

Details by (mod) - legal points of discharge for HVACR condensate

Anon:

According to the model plumbing codes and mechanical codes such as the UMC sections

UMC 309, UMC 815.2.2, and UMC 1105.10,

Condensate from an air conditioning or heat pump system can be discharged to "... other points of discharge acceptable to the municipal authority."

Here is a typical guideline for disposal of air conditioning or heat pump condensate from a commercial facility.

2. Condensate from commercial & industrial air conditioning units must terminate in the following order:

i. To a landscaped area or landscape-based stormwater treatment system (e.g. bio-retention unit) that is properly-designed to accommodate the volume of condensate;

or

ii. To the sanitary sewer indirectly. Discharges to sanitary sewer system shall be subject to all wastewater permitting requirements and fees – contact the Environmental Services Department;

or

iii. If the two discharge options described above are not feasible, as determined by the authority having jurisdiction, then these discharges may indirectly enter the storm drain system.

Source: BULLETIN #256 02/10/16, Condensate Disposal Requirements, San José Permit Center, San José City Hall, 200 E. Santa Clara St., San José, CA 95113
408-535-3555 www.sanjoseca.gov/building retrieved 2018/05/11, original source: www.sanjoseca.gov/DocumentCenter/View/53974

Also available at InspectApedia.com at inspectapedia.com/aircond/AC-Condensate-Disposal-Guide-San-Jose-CA.pdf

The reason we don't connect condensate discharge piping *directly* or hard-piped to a sewer or storm drain (nor directly into a plumbing system vent pipe) is risk of explosive or unsanitary sewer gases being drawn into the building's HVAC system. That's why air gaps and traps are required for such connections, making the connection "indirect".

Watch out: you absolutely must check with your local building or plumbing code enforcement officials about your HVACR condensate disposal plan as municipalities vary in what they permit.

In that discussion it is essential to be perfectly clear and honest about exactly what is in your condensate drainage. For example, does the condensate contain biocides, chemicals, treatments that may not be properly discharged into the environment. Knoxville's guidelines address this concernb:

It is allowable to discharge condensated water, which is essentially pure water from the atmosphere. It is illegal to discharge any water that contains chemicals, detergents, algae-killing agents and other manmade substances onto the ground or onto any surface which drains to the city stormwater drainage system, ditches, swales, curbs, natural creeks and streams or wetlands.

Source: IC-12 Air Conditioners & Refrigeration, [PDF] City of Knoxville TN Engineering Department (2003) retrieved 2018/05/11 original source: http://www.knoxvilletn.gov/UserFiles/Servers/Server_109478/File/Engineering/BMPManual/IC-12.pdf

A copy of this bulletin is also available at Inspectapedia.com at CONDENSATE DISPOSAL CODE TN https://inspectapedia.com/aircond/AC-Condensate-Disposal-Knoxville-TN-2003.pdf

Also see CONDENSATE DISPOSAL REQUIREMENTS, California Building Code (2013) [PDF] retrieved 2017/07/17, original source: https://docs.vcrma.org/images/pdf/bs/2007_Adopted16A_Revised-1-20-2010.pdf as adopted by Ventura County in 2010

Reply by Joe

That's great information, I really appreciate it!

Is there a way to tap into the A/C condensate to water my plants

We live in an area of frequent severe drought. The condensation water is currently running down the wall into a large (56 qt) storage bin, which fills up frequently when humidity is high and we are running the a/c a lot, that is, when it is very hot outside.

. Which is just when we are forbidden to water more than once/week and the plants need water the most.

When the contractor puts the outside downline in, I wanted a way to tap into the water flow to drain it off into a bucket and use it to water my plants.

Something like a special faucet perhaps, but nothing that will blow the integrity of the line.

They say that is illegal, but they have told me this on other things and when I have researched it, what I wanted was just fine, even ok'd by the head of the city inspectors' dept.

I don't really know where they are going to take the water, but it seems a hideous waste to just pour it into a sewer when we have such an enormous need for water right when this condensate is most likely to be in high volume.

I am 70 yrs old and so not going to be lifting heavy things, but a couple of buckets and a rolling carrier and I can take the water wherever it is needed, a cpl of loads per day -- if I can get at it when I want to.

Do you have any ideas how this could be arranged -- legally and safely? On 2016-08-30 by rahur

Answer by (mod): unsafe, unhealthy A/C condensate water risks

A/C condensate, particularly when stored, risks brewing pathogenic hazards such as Legionnaire's disease.

It would be better to use the condensate for watering plants than to keep it in storage, where it certainly would not be safe to drink without various filtering and disinfection steps.

I suggest asking your local health or plumbing inspector for an OK letter that includes a tap to permit use of condensate for plant watering.

Condensate Trap FAQs

Can a condensate trap be shared?

Can appliances share condensate traps. For eample, can a tankless water heater condensate line share a drain line with a furnace condensate drain line. On 2019-03-09 by Matt

Suggestion by (mod) - bad idea in your case

Possibly, but typically the Trap is provided quite close to the Appliance so it seems unlikely to me that your solution is a good one

Can appliances share condensate traps.

On 2019-03-09 Matt asked: Can appliances share condensate traps.

For example, can a tankless water heater condensate line share a drain line with a furnace condensate drain line?

I have the same question.

Specifically, I'd like to combine the condensate lines from a hybrid water heater and a/c air handler. Anyone have an answer, please? On 2019-08-22 by Ted Brandt

Answer by (mod) - An air conditioning or heat pump condensate trap can be shared if it's of adequate size

Ted

A condensate trap can be shared if it's of adequate size and of course if other concerns for piping distances, slope, etc. are met. In fact it's common to see multiple A/C condensate drains taken to the same trap or drain.

Are P-Traps required on Condensate Drains?

Are p-traps required On 2018-06-30 by royalrayhewlett@gmail.com -

Answer by (mod) - Traps are required - may not be a "P" trap.

Royal

Condensate drains must be trapped. Otherwise you risk drawing sewer gases up from a building drain into the air handler and blowing not only smelly but potentially un-sanitary or even explosive sewer gases into the building.

An alternative that is acceptable in many jurisdictions is to drain the condensate via an air gap into an existing trapped drain, such as some shown in Carson Dunlop's sketch at the top of this page.

Also per UMC 309, UMC 815.2.2, and UMC 1105.10,

Condensate from an air conditioning or heat pump system can be discharged to "... other points of discharge acceptable to the municipal authority."

Condensate Drain Line Connection & Routing FAQs

What is the required clearance distance between the condensate pipe and the roof deck?

What is the code on running a/c lines in attic what is the clearance between the pipe and the roof (plywood) so roof nails cant penetrate lines in Florida thank you On 2016-04-07 by John

Answer by (mod)

John, usually the refrigerant lines are run in or on the attic floor, but if you need to run them under the roof, I'd follow the same guidelines as for electrical wiring: that is, you either mount the lines to the interior edge of the rafters or if you must run a line through a rafter you'd drill the passage hole in the *center* of the framing member.

That minimizes any impact on structural strength of the member and also should be deep enough or far enough from the roof surface to avoid a nail puncture.

Finally, if you must run refrigerant tubing or a condensate line or a wire or pipe of any sort through framing where its location exposes it to a nail puncture, you must protect the tubing etc. from puncture by using a nailing plate.

See REFRIGERANT PIPING INSTALLATION SPECIFICATIONS   On installing refrigerant piping or condensate lines,

and also

see ELECTRICAL WIRE CLEARANCE FROM DUCTS & PIPES 

Watch out: don't run condensate drain piping touching nor within a couple of inches of the roof deck lest roofing nails puncture the drain line.

And where any plumbing or conduit run through a framing member where a nail into the member might puncture the pipe the pipe needs to be protected by a nail plate.

How far does this pipe need to be insulated in a suspended ceiling?

So my ac guys are running the condensation drain pipe through a hanging ceiling. How far does this pipe need to be insulated?

They are telling me only ten feet from where it drops in through the roof, however I was told it needed to be insulated all the way to the drop down at the wall where it would then tie into the sink drain. Please advise. Thanks On 2016-03-23 by james

Suggestions by (mod)

I'd insulate where needed to protect from freezing and to protect from exterior condensate forming on and dripping off of the line into the ceiling space.

If none of the line is exposed to these conditions none of it needs to be insulated.

Where do I connect a pumped condensate drain to the gravity drain?

I have 2 fan coil unit condensate lines draining to a floor sink, however 1 of them needs a pump because of obstructions.

So once the line comes up over the obstructions can I connect the pumped condensate line into the sloped condensate line from the other fan coil unit and if so does it have to connect to the top of the sloped line? On 2015-08-22 by Confused

by (mod) where to connect condensate to the drain

You can connect the pumped condensate drain into the sloped gravity drain using a TEE and entering from above provided that the second line is of adequate diameter.

- yes the top,

or you'd need a check valve in the pumped line

by Confused

yes they are both 3/4". Thank you very much for your help, it is greatly appreciated!

Tennessee code re condensate drain connections

In Tennessee does the code require condensate drain connections be glued with PVC cement when ran verticle. Thanks. By the way, this is a split system with air handler in attic On 2018-05-03 by mwjenkins01@gmail.com

Details on Tennessee Condensate Drain Code Gluing by (mod) -

MW

Tennessee has adopted the International Plumbing Code 2012 (IPC 2012)

from which we excerpt:

705.2.2 Solvent Cementing

Joint surfaces shall be clean and free from moisture. Solvent cement that conforms to ASTM D 2235 or CSA B181.1 shall be applied to all joint surfaces.

The joint shall be made while the cement is wet. Joints shall be made in accordance with ASTM D 2235, ASTM D 2661, ASTM F 628 or CSA B181.1. Solvent-cement joints shall be permitted above or below ground.

All model building codes and state codes in the U.S. that describe condensate drain piping will require that the piping be properly-installed, connected, routed, and drained to a proper destination. A condensate drain using plastic pipe that was just "friction fit" and not glued, would leak and so would not be acceptable.

Excerpting from Chapter 3 of the Uniform Mechanical Code UMC for handling condensate - condensate disposal codes

[M] 314.2.1 Condensate disposal. Condensate from all cooling coils and evaporators shall be conveyed from the drain pan outlet to an approved place of disposal. Condensate shall not discharge into a street, alley or other areas so as to cause a nuisance.

[M] 314.2.2 Drain pipe materials and sizes. Components of the condensate disposal system shall be cast iron, galvanized steel, copper, cross-linked polyethylene, polybutylene, polyethylene, ABS, CPVC, or PVC pipe or tubing. All components shall be selected for the pressure and temperature rating of the installation.

Condensate waste and drain line size shall not be less than 3/4-inch (19 mm) internal diameter and shall not decrease in size from the drain pan connection to the place of condensate disposal.

Where the drain pipes from more than one unit are manifolded together for condensate drainage, the pipe or tubing shall be sized in accordance with an approved method. All horizontal sections of drain piping shall be installed in uniform alignment at a uniform slope.

Can I drain my dehumidifier condensate right into my sewer pipe?

Can I install a hose for a dehumidifier into my main waste pipe? On 2018-04-26 by Noreen

Answer by (mod) - Not directly

Through a trap or trapped drain, yes. Not as a direct, hard-piped sealed connection - that'd be a cross-connection and could make the dehumidifier an unsanitary source of bacterial growth and contamination.

What's East Texas code on home-made seepage pit for condensate disposal

I have an old AC drain through the slab which terminates outside underground at what looks like a 5-gallon bucket turned upside-down over a gravel bed with no cleanout access.

Is that and acceptable discharge system in East Texas? If not, what would be better? On 2015-09-02 by Roger

Reply by (mod)

Sorry to duck and weave and arm-wave but the truth is your local building code compliance inspector is the final legal authority on a question such as this.

Some jurisdictions don't permit any wastewater discharge to the ground surface but might buy discharge into a seepage pit.

My OPINION is it sounds as if someone made a home-made mini seepage pit intended only to catch A/C condensate.

The worry would be a fatal Legionnaire's disease bacterial infection that might occur IF the condensate drain is not properly piped and trapped.

See this example DALLAS PLUMBING CODE for HVAC CONDENSATE PIPING [PDF]

Why can't I connect commercial A/C condensate drains to a sewer line?

Why in the commercial industry are you not permitted to discharge a/c or fan coil units condensate into a foul water drain only into rainwater drains? On 2016-07-15 8 by Ian Pyett

Answer by (mod) why not dump condensate into a foul water drain?

A guess would be concern for backdrafting of unsanitary or explosive sewer gases into the building through the air handler.

Can I connect multiple condensate drains together to a common main line?

Can I conect three primary condensate lines together?
And I like to connect three secondary condensate line together as well?

Do I need to increase the size of the pvc pipe or it can all go in to 3/4" line and out?
I have two FAU units and one tankless water heater all in the attic in the sale locations. On 2016-09-16 by Slava

Answerby (mod): yes if proper size drain line isused

Slava

One can join condensate drains to a common one if the drain slope and diameter are adequate to handle the flow rate. I'm not sure how the tankless water heater is involved in the discussion.

Condensate Drain Line Slope FAQs

What's adequate slope on a condensate drain?

If i have codensate pump with 6ft hose running vertical and last 8 inches with a downward slope to the outside is that ok for proper drainage?

Since theres always water in remaining 5ft of tubing there would be no back pressure to the pump correct? And since last 8in is on downward slope that would eliminate the possibility of potential freezing correct? On 2018-01-25 by Anonymous

Reply by (mod) -

Anon

There is a six-foot back-pressure (2.6 psi) on the pump presented by the six feet of water-filled tubing above the condensate pump.

The output of any pump is limited by head pressure - the amount of lift that the pump has to provide.

Typically a condensate pump's specifications include both the pump's horsepower (usually a fraction considerably less than 1hp, possibly 1/50 hp or 1/30 hp) and the pump's lift height - the maximum height to which the pump can lift condensate, and possibly also the gpm flow rate the pump can achieve at various lift heights.

Or the manufacturer may give the pump's flow rate with zero head pressure, leaving it to you to guess at the flow rate when there is a lift involved.

But since typical HVAC condensate pumps are rated for between 16 ft (6.94 psi) and 22 ft (9.54 psi) of lift your lift height should not be a problem.

I cannot promise that your system is freeze-proofed. That depends on the installation, location, exposure to temperatures.

For example, if the water-filled tubing is close to an exterior wall and is not protected from freezing, your system could freeze up.

Trouble with freezing condensate drain line

Had a new heat pump system installed 2 years ago, replacing old one. Since then, drain line has frozen in extreme temps and backed up into laundry room.

I see here that there should be 1/8" per foot slope which i will check. I doubt they put that much on it. Is it supposed to have a trap? On 2018-02-01 by JMP

Answer by (mod) - Slope the drain so as not to hold water, and Section 407.2.4, Traps, requires that "Condensate drains shall be trapped as required by the equipment or appliance manufacturer

Section 407.2.4, Traps, requires that "Condensate drains shall be trapped as required by the equipment or appliance manufacturer." We interpret this provision to defer to the equipment manufacturer's installation instructions.

Watch out: in our OPINION and as we discuss in these articles, while a trap on a condensate drain line, usually provided quite close to the condensate collection pan itself, can reduce the chances of sewer gases backing up from a condensate drain that has been connected to the building DWV vent piping (not a procedure we recommend), a conventional P-trap in the condensate drain will not protect against all sewer gas backup possibilities.

In particular, when an air conditioner is shut down for long periods of time (say during the heating season) it is common for the water condensate contents of the trap to dry out, thus losing protection against sewer gas leaks backing up through that system.

Condensate Drain Disposal / Termination FAQs

OK to dump A/C condensate under our basement slab?

Our installers have placed our drainage line for our HVAC system in concrete that appears to run under the foundation of our basement. I do believe it rund at least to the gravel under the foundation I do know that it is not contented to another pipe to the exterior of the home. Is this ok? On 2017-11-06 by Joe M

Answer by (mod) - No

Joe

I'm not sure what's going on at the system you describe.

Generally I think it's a bad idea to just dump wastewater under a slab - inviting a water entry problem somewhere in the building and maybe dumping into an unreliable disposal point, or increasing basement moisture levels that in turn invite a mold problem.

Is it OK to dispose of Condensate into the house crawl space?

Is it OK to drain the condensate in a crawl space under a house On 2015-07-29 by Charles

Answer by (mod): NO

I would not dump AC condensate into a crawl space. The risk is elevated moisture, mold contamination, and contaminants entering the building.

I'd make an exception IF the condensate were pouring directly into a sump pump or other pump that is disposing of the water outdoors or to a sewer drain.

OK to drain HVAC condensate into a toilet tailpiece?

I am working in a multiple unit apartment complex. Can i drain a condensate line from a common area to a lavatory tailpiece in a private unit? On 2017-03-31 by Garrett

Answer by (mod): NO

I'm doubtful that this is a good approach. First I want to see an air gap between the condensate discharge and the drain into which it is discharging. I'm doubtful that you can do that when you pipe horizontally through wall into a plumbing trap at and adjoining units sync. II there maybe liabilities as well as actual hazards for the documents from a leak or from bacterial hazards.

First I want to see an air gap between the condensate discharge and the drain into which it is discharging.

I'm doubtful that you can do that when you pipe horizontally through wall into a plumbing trap at and adjoining units sync.

Also there maybe liabilities as well as actual hazards for the occupants from a leak or from bacterial hazards.

Condensate Drain Size & Pests FAQs

How do I keep pests out of the condensate drain

If a condensate drain is outside and at ground level how do you keep insects or rodents, etc out of the drain? On 2017-10-13 by Anonymous

Answer by (mod) -

The drain diameter is normally so small (3/8 or 1/2") that rodents are not an invasion problem. Drainage of water seems to keep out mud daubers. But certainly if you're having trouble you could screen the end of the outlet.

Watch out: Take care to inspect the screen periodically to be sure it's not algae clogged or your condensate drain could back up and leak into the building.

Mice came in the condensate drain opening and chewed our unit's wiring

I purchased 2 Mitsubishi Mr. Slim Split Air Conditioners and Heat Pump Systems two years ago.

One unit stopped working and it was discovered that mice had chewed the wires in the outside condensers because these units have a 1 ⅝” manufacture installed drainage hole.

With holes this large, many animals are likely to venture inside. I need to purchase another air conditioner unit but am not going to buy another Mitsubishi because of this issue. Do all mini splits have such a large drainage hole in their units? On 2016-06-03 by Anonymous

Comments by (mod) Mitsubishi Mr. Slim Split Air Conditioner and Heat Pump System condensate disposal vs mice

Anon I would not blame the manufacturer for a mouse problem; I'd clean up whatever food is attracting the mice, use services of a mouse exterminator, fix the AC wiring and seal the mouse openings.

Also double check the required size - diameter - of your condensate drain opening - that 1 ⅝” diameter may be bigger than necessary.

Condensate Drain Line Clogging FAQs

Why is condensate dripping on the floors of our apartment buildng?

In a 34-unit apartment building, why does condensate drip on the floors from most of the apartments' fan coil units? On 2015-08-07 by Anonymous

Suggestions by (mod) why is condenate dripping out of the fan coil unit and onto on the apartment floor ?

Anon:

Typically the condensate pans are clogged, missing, leaking, improperly installed, or the condensate drains are clogged as discussed in the article above.

How do we stop clogging in or condominium condensate drain system?

I live on the 2nd floor of a 4 story condo. The PVC condensation pipes of the 2 units above me and the unit below me connect to a common area vertical PVC pipe (presumably dedicated to condensation disposal).

We periodically pour vinegar into individual unit pipes to keep them clean but it's not preventing clogs in the common area pipe.

A water detection device will shut off my AC if it detects a backup but it won't shut off the AC of the units above me, so it still backs up into my unit.

Any suggestions on how to do preventive maintenance on this system? Thank you. On 2015-07-17 by Bob Collidge

Suggestion by (mod) recurrent condensate drain clogs

The reason for recurrent clogs in the condensate drain system needs to be found and corrected.

Regular use of drain cleaners or any other un-stopping material is not a good substitute for proper installation and design of the condensate system. I suspect there is a piping problem: routing, slope, diameter, distances, termination points, or possibly failure to trap condensate drains and screen against lint or debris entering the system.

The condensate sensor switch that shuts off your system can be wired to shut off others too, or if necessary multiple switches each sending to an individual AC unit can be mounted in the same sensor location.