The HHIC guidelines for condensate discharge pipes should be connected to an internal gravity discharge, and external condensate pipe insulation should be sealed to prevent freezing. The discharge pipe must fall at least 45mm per meter away from the boiler and take the shortest route. External condensate pipes are highly prone to freezing over, so it is recommended to defrost affected pipework as soon as possible.
A condensate pipe’s primary function is to safely channel acidic waste water produced during a boiler’s condensing process to an external drain. Modern condensing LPG, oil, and gas boilers have this function. The smart, long-term solution is to neutralize the acidic content in the condensate waste before it enters any piping. It can also injure septic systems, so for homes with septic tanks, condensate should be discharged into an external soil stack. However, the HHIC only allows it if the downpipe makes its way to a combined system.
If the condensate is discharged into the house’s drainage system, it must be through an indirect waste pipe. If the condensate is drained into an external soil stack, an engineer can fit an air break to prevent sewage backing up into the boiler condensate pipework and avoid costly damage in a serious blockage. Pumping the acidic waste outdoors or into sanitary sewers could contaminate groundwater or degrade local water infrastructure.
Condensate from both air conditioner units and condensing boilers is slightly acidic and can be discharged into a soakway filled with limestone chippings, at least 2 meters away from the property. The smart, long-term solution is to neutralize the acidic content in the condensate waste before it enters any piping.
📹 Air Conditioner Condensate DRAIN TRAPS! Function, Problems, Cleaning, Air Loss! Do I Need it?
In this HVAC Training Video, I Show IF/WHEN to Install a Water Drain Trap such as a P-trap, U-trap, Dry-Trap on a Furnace & AC …
Where should condensate drain to?
It is standard practice to terminate condensate drain lines at the side of the house, typically at a distance of six inches from the ground. This location allows for the absorption of the necessary amount of drainage by a planted area, which then allows the water to soak into the earth.
Can condensate drain go into rainwater?
A condensate pipe may be connected to a rainwater downpipe, which then connects to the foul waste system. Nevertheless, it is recommended that the external run be kept to a minimum and that a pipe diameter of 32mm be maintained at the point of exit from the property.
Can a condensate pipe go into the ground?
Lagging is a crucial preventative measure for condensate pipes, especially those above ground, to add insulation and ensure their functionality during colder winter months. Professional installers should include lagging as a standard. If the lagging doesn’t work, it’s essential to have someone inspect the boiler. A fully qualified, highly-trained professional should be involved, confident in their work and understanding manufacturer’s guidelines. If the boiler still doesn’t work after removing ice, it’s best to have someone inspect the system.
How do you empty condensate?
To clear a condensate line, locate the drain line, create an air-tight seal between the wet/dry vac and the drain line, and use the wet/dry vac to remove all water and obstacles. Pour a small amount of bleach down the drain line to keep it clear in the future. Condensate lines can cause appliances to stop working, especially in the middle of winter, and can cause water pooling around a reversible heat pump. Knowing how to clean the line yourself can save money and heartache during the middle of winter.
Heat pumps, which move heat into a home during winter by reversing the process it uses to move heat out of a home during summer, generate a lot of condensation, which is usually drained outside the home. This condensation is also responsible for the effective reduction of humidity in a home.
What are the rules for condensate drain lines?
It is imperative that the dimensions of the condensate waste and drain line remain consistent from the drain pan connection to the designated disposal area.
What would happen if condensate is not removed?
The steam supply system can suffer from dangerous water hammer if condensate is not removed. This occurs when liquid condensate fills the pipe’s cross-sectional area and is propelled by high-velocity steam against the pipe walls. Condensate return systems can significantly impact productivity, energy efficiency, and site reliability. Engineers often focus on improving steam supply issues like piping leaks, steam trap leaks, and insulation, but rarely address the condensate return system.
Common issues include high backpressure, knocking, and pipe damage caused by high backpressure or knocking. Plant personnel are typically more concerned with steam supply and heat for manufacturing units, but a condensate return system can significantly impact production, efficiency, and reliability.
Where can I discharge condensate?
Condensate drains should not directly connect to any plumbing drain, waste, or vent pipe, and should only discharge into floor sinks, trench drains, mop sinks, hub drains, standpipes, utility sinks, or laundry sinks. Connections to lavatory wye branch tailpieces or bathtub overflow pipes are not considered discharging to a plumbing fixture. The point of discharge should be within the same occupancy, tenant space, or dwelling unit as the condensate source.
Why do you need to neutralize condensate?
Untreated condensate can deteriorate septic systems by causing acidic waste to react with good bacteria in the waste, leading to the death of the bacteria. Good bacteria are essential for breaking down human waste, ensuring proper movement through the septic system. Without good bacteria, septic systems can become backed up, causing major problems for cities and towns. Untreated condensate also harms the environment and groundwater by contaminating and killing vegetation, leading to dead grass and plants, and polluting groundwater, which often flows into lakes, rivers, and wetlands.
What would happen if condensation was removed?
The water cycle, which encompasses the evaporation of liquid water on Earth and the transpiration of water vapor, would be terminated if there were no condensation stage, as precipitation would cease and the cycle would be terminated.
How do you dispose of condensate water?
Plant managers are advised to conduct a visual inventory check of their compressor system installation to ensure compliance with environmental regulations. The inspection should reveal condensate drains at the rear of compressors, dryers, filters, and wet air receivers. If these drains are ideally directed to an oil/water separator, the treated condensate can be drained without damaging the environment or violating water pollution regulations, provided the site has a consent to discharge notice from their local water authority.
If the condensate is drained directly into a floor or standard plastic container, action is needed. Oil/water separators are easy to install and operate, but disposal rules can vary regionally. Companies must obtain a Permit to Discharge or an exemption from the Environment Agency before any disposal procedure takes place. For further advice on condensate management, contact the compressed air system supplier.
Can condensate drain to the outside?
The trap, a shallow U-shaped bend, traps gas from drainage lines and continues the AC condensate drainage pipe to the outdoors or other structures. Mismanaged condensate can lead to mold, mildew, bacteria, and pests in dark, wet environments. Air conditioning coils produce a lot of condensation, which can damage the AC system, home, and health if allowed to pool or overflow. Incorrect sloped drain pans and lines can cause condensate water to collect and pool in the AC drainage system, leading to mold growth and clogging of drain lines.
📹 The Facts About AC Condensate Drain Lines
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For 13 years my Nordyne 4 ton unit drained out what I thought was a pretty good condensate “drip”. It had NO p-trap. After perusal a previous article you did, I installed the Rectoseal trap and turned the condensate drain into a small garden hose. Everything equal, I dropped the RH by 5%. To test how well this works I opened up the cap between the trap and air handler and added food coloring and let the unit run. The food coloring just sits there. Closed the cap and off she goes.
Here in Florida the majority of houses are built on slab foundations with the line set and condensate line running under the slab in 3 or 4 inch pvc. The exit point for the condensate line is outside the house and rises up 8 to 10 inches above ground level. This creates a natural “P” trap as the under slab vs the exit point in total is about 15 inches, trapping the water in the line. Therefore no “P” trap is necessary. Depending on your construction it may or may not be necessary to add a “P” trap.
Wanted to comment on your latest vid in the hopes you see it. I spent hours perusal your articles in order to fix my HVAC system. I know you teach to help the pros but I hope you dont mind that you help a lot of DIYers like myself. I took the time to watch many articles on your highly accurate and detailed inspections and repairs of HVAC systems and in the end I was able to fix it myself. Thank you so much for all of the articles and just know youre helping so many. Cheers!
I just had a new Goodman installed and when I asked them why they didn’t use a P-trap they said it didn’t need it because the condensate line comes out of the bottom. I knew that wasn’t right but I did read in the manual that if you have a shut off installed then you don’t need a P-trap necessarily but I’m not sure if that’s a good idea. Meanwhile these guys who installed it seem like they don’t know what they’re doing because they didn’t mention that all they said is because the PVC pipe comes off the bottom of the air handler you don’t need a P-trap meanwhile even though the pan is draining there is a small leak where are the threads attached to the pan. To show you what kind of workers they are in order to try and fix the leak they hit the PVC pipe with a hammer to break it off then they replaced it but didn’t use any plumbers tape so it’s still leaking a tiny bit. Maybe it wouldn’t be leaking if they had a P-trap even though it’s not really backing up in the pan much at all. I can’t trust these guys that’s for sure. I also have a little bit of water dripping off the coil and not going into the pan. I mentioned that and of course they’re playing dumb. Not sure what I’m going to do about that
Wow 😮 Now I’m even more freaked out. I’m a first time homeowner. I watch these articles all the time trying to learn what I should be doing. My AC is on the second floor in a closet. It ducts out from there. Another article told me I should flush the pvc drain pipe with vinegar. But my drain pipe had no cap to open to pour in vinegar. Apparently that’s not unusual because there was a article for how to cut a T valve in. But now you added a p-pipe. I don’t have that either. Where does that go? Before or after the T-valve? The prior articles just warned that the drain pipe had to slope down from the AC. 😱
Best article ever 10 stars and 10 thumbs up. Specially now that I am about to install a heat pump and I had been searching for this answer since I didn’t know the requirements for it and also because I new ducted and ductless work differently and also because I was debating whether to drain it outside or inside into a drain or even a pipe that drains my kitchen sink but was concerned about sewer gases backing into the drain pipe.
So let me know if I have this right… The reason the unit on the left (Furnace/AC) has positive pressure at the A-Coil, and the unit on the right (AC) has negative pressure at the A-Coil, is because in the Furnace/AC (left unit), the blower is below/before the A-Coil (often between the A-Coil and the filter/return duct) blowing toward the C-Coil, and on the AC (right unit), the blower is after/above the A-Coil, blowing AWAY from the A-Coil.
Ok my son purchased his first home and now is working out of town. So I have trying to help out at his house so his wife does not have to do everything. Noticed the other day water coming out a pipe in the eve of the house. So I knew it was the emergency over flow for the HVAC. When I get in the attic I notice that the water seems to be coming out I guess the emergency on the HVAC and air flow. On the main drain line that goes to the house plumbing seems the be clear flowing. Almost seems like the safety switch on the main line slows the flow or change air pressure to make it some out the emergency hole. Do know they had some warranty work done on the a/c and am wondering if they left out the drain. Will try to attach a picture so you can see what I’m talking about. Any ideas would be great!
The air escaping in your math scenario is 15.8 cfm, not 4 cfm. You forgot radius squared. Not sure why it’s acceptable to allow a loss of 15 cfm from any positive system. This would be the same as having a one inch hole in your ductwork. This makes a compelling reason to have a trap on a positive pressure system, to prevent air escaping. Nice job demonstrating the physics.
With the second example shown (positive pressure system) I noticed the shut off valve is slightly higher than the drain vent. From the little bit of research I’ve done people stated that it’s faulty and did not work as it should. That in order for the valve to be triggered it needs to sit slightly below the drain vent. Is this true?
My Furnace & A coil didn’t have a trap on it for 10 years when I moved in this old house. I seen a article online and it showed the water trapped in the pan because of no trap. I looked at my unit. It had no trap. I looked while the unit was running and the condensate was pooled because of negative air flow. It looked just like this article at 3:08 min. I put a U-trap on it a few yeas ago. The u stays full of water now. When I pull the cap, I noticed positive air flow. Why would it have negative one time and positive later on? I went to HVAC school, but I don’t use that knowledge except for my personal house.
My drain line was plugged up and overflowed into the secondary pan, but I don’t understand why the float switch which is attached next to coil drain didn’t tell the system to stop? I pulled the float switch out and verified it does shut off the outside unit when moved, but don’t know why it wouldn’t shut off the unit before it started overflowing into the secondary pan. I have no P trap.
Great article. In some positive pressure situations, a trap may still be needed. There’s a youtube article out there where they use a clear evaporator chamber where the positive pressure is high enough to cause the air flow escaping from the drain to actually push the water away from the drain hole preventing it from draining until the system shuts off. It’s similar to what happens with negative pressure but there’s positive air flow pushing through the drainpipe. A trap in that case will prevent that. It will also prevent the loss of conditioned air escaping. However, in the case of the overflow, when it is drained outside the house, air will always be able to escape the system. A trap on that line won’t help because it won’t fill with water until the main drain clogs. Not a problem if you use an overflow switch. Forum threads on these p-trap topics go on and on and never seem to resolve to a solution for all cases.
I looked this up because I’ve been working in my attic, and since it’s transitioning into winter, it dawned on me that the water in my condensate P-trap will more than likely dry up since the AC is not being run. So I take it I should keep an eye on that in the winter and add water to it if I need to?
Just found your website. I have been having HVAC/Furnace issues with my drain line so have been looking at YouTube to better understand what I don’t know. I have seen a lot of articles on drain lines, p-traps, air exchangers and exchange coils and this is THE BEST of all that I have seen. Your explain the different requirements for air handlers HVAC), exchange coils (Furnace), and mini split systems. FANTASTIC. Thank you!
We just had furnace/air handler/AC units /Evaporator Coil (A coil) and outside unit replaced… as well as a new condensate pump. I went downstairs and noticed that the pvc that comes out of the furnace and drains to the condensate pump has a piece of open pvc on the top of it, and AIR IS BLOWING OUT OF IT. IS THIS NORMAL? Does this decrease the air flow coming out of the furnace and/or AC unit into the ducts?? SHOULD it be open? Shouldn’t the pipe to the condensate pump be closed?
Question – we have a gas furnace & A//C system and the unit in your article is right on top of the American standard freedom 80vs (the air filter is at the bottom of that for reference) anyway it’s all in a 2ft Wx 9.5ft H closet that’s in our laundry room… yeah it’s all weird idk. The pvc lines coming out of the unit your talking about in this article don’t have those black rubber seals or anything sealing the open area around where they enter or exit the unit. Cold air just blows right out them into the closet. Is that ok? Should we have them patched around? Trying to figure out where any and all air leaks can be sealed. Thanks 😊
The condensate drain on my 90%+ furnace is completely dry. I was going to pour bleach in there as instructed by my installer to clean it. I saw it was dry, which I had never seen before. Is it normal for this to become dry during the months that the furnace isn’t being used to heat the house, only the A/C is being used. Also, did you say that if my drains are not going outside but just draining into a floor drain that I didn’t need a trap? The furnace (heating) condensation drain has a sort of trap but not a conventional P trap. Two tubes come out the side of the furnace into the very bottom of a retention reservoir. The reservoir will fill up then overflow into a drain connected to the PVC drain that goes to my floor drain. That reservoir is what is dry right now. My A/C condensation drain comes comes out of the top part of the furnace/AC where that A coil is. The drain then makes a couple 90% turns and is connected to the same PVC that the heating condensation drain is connected to and drains into the floor drain. The A/C doesn’t appear to have any sort of P trap. Is that okay or should there be a P trap. If pictures would help, I have some I could send you.
I have a commercial AHU drain question. The drain pan inside the motor housing, when the unit is cooling, is constantly full/overflowing and water is not draining through the trap, but when you open the door to the motor housing water begins draining out of the trap. There’s clearly a vacuum effect happening because the door is hard to open. What could be done to fix this issue? The condensate overflows the pan inside and the water level is about as high as the bottom of the door and leaks out of the unit wherever it can, just not through the condensate trap like it should. Any help would be greatly appreciated
It’s crazy how all the math makes sense when actually applied in the real world. I got Ds and Fs in all my high school math but when it’s actually used for a practical purpose all the formulas make sense. Why the hell don’t they teach math this way instead of hypotheticals where someone is buying 4 trillion watermelons?
Getting ready to install new Trane 4-5 ton coil. In the installation instructions, it states: “The condensate trap is not mandatory but is recommended for efficiency”. But after perusal this article it would seem that a trap would be mandatory because otherwise the condensate water would not drain until the unit shut off. Any further explanation?
I moved from Florida to Oregon. Combo unit furnace central A/C. Notice no water coming out the condensate line outside the house. Air is quite dry though. Notice that on my unit the pipe just above the U trap has a plug (between the coil and the U trap) that is not covered – so open to air. Is that wrong and should that cap not just be a open pipe but closed top?
Good morning, perhaps someone on here might be of assistance with a condensate drain issue I’m at a loss trying to figure out. I have a 3.5 ton Goodman package heat pump, it is a draw through design, it only has one drain fitting. The trap was made with some 3/4 inch 90 elbows, the bottom of the trap is about 6 inches below the base of the unit, and the outlet of the trap is about 4 inches below the base of the unit. I cannot, no matter what I do, get it to drain while the unit is running, it will only drain when the blower shuts off, then water pours from the trap for about 45 seconds or so. The unit is not pulling the water out of the trap, I’ve stuck my finger in the trap while it’s running and the trap is full, it’s not sucking air in the drain either as I’ve held a piece of tissue paper up to the outlet of the trap while the unit it running an there is no movement to the paper at all. Clearly either the blower is sucking water from the pan and/or the pan is overflowing as the last PM I did about 2 weeks ago I found that the blower was covered in moisture and the bottom of the air handler side of the unit had about 1/4 inch of standing water in it and the insulation on the bottom of the box was saturated. Any ideas what might be causing this? Could it have excessive negative pressure? The unit has a single 14 inch flex return, the filter box is a 14×20, the supply is also 14 inch flex that is wye’d off into 2 plenum boxes under the house, each plenum box feeds 5 vents, each supply vent is fed with 8 inch flex, the individual supply vents are 4×8’s The unit is fairly level on the pad, if anything it’s very slightly sloped towards the front which should provide gravity assistance to the drain.
Hi Craig, I guess this article was just for Air Conditioning coil drains but what about a 95% condensing gas furnace. My basement goodman furnace has a couple 1/2 inch tubes exiting the furnace burner section and dumps into some kind of gray plastic box trap they send with their furnace’s, then dumps into the open drain or condensate pump. Is that trap necessary? This is in addition to the 3/4 inch pvc drain line coming from the cased coil drain pan above.
I’m not in the trade but one thing stood out to me about the use of an existing p trap. If you select a p trap that may not get regular use like a second shower for example the p trap can go empty due to evaporation and send gasses up into the air handler when a p trap is not used at the air handler. Seems easier to just put one in by default.
As a homeowner, I prefer the lettering on the pvc piping to be exposed for easy viewing. That goes for model #/serial # of equipment for future reference/repair. Also, I would thin joining two separate condensate lines to one run is not appropriate because if the final run gets clogged then both systems are clogged. Not a tech here, but common sense.
My existing drain line is bowed in the middle, slopes up toward the exit, no P trap, 12′ with no support straps, and no clean out except through inside the heater condensation tubing. The drain line is sandwiched between the flexible duct and a stim wall. Day & Night (Carrier) inside drain goes into a black plastic can before attached to line. Couldn’t get Carrier to answer questions on this can! This can has allot of brown stuff. Is that normal? A mess! Help!
Very much appreciate your great explanation. After perusal this and see what happened to evaperator leak on the house we bought 2 years ago I found it very helpful to understand why we got problem. Whoever service/install the system was so careless about what he did. It was not up to mechanical standard and common sense logic. My unit problem is inevitable when the humidity high which rarely happen in S.Cal. Equipped with your info I will fix the issue and save the money. Thanks
, why would it be a good idea to let the condensate drain right beside the house, and be allowed to drain right into the foundation drain of the house? You see….french drains around your home are only for occasional backup of water. That may be ok in the West. But, in the south east, the humidity levels are so high, that an average a/c unit for homes, can produce 30-40 gal of water per day. You definitely dont want your foundation drain to be used half the year in the summer to catch slow drip from an a/c unit, I just finished a job, where the homeowner thought they had a irrigation leak. Turns out, their small back yard was staying soaked, because the ac condensate was draining into their foundation French drain system. The french drain was dispersing the water across the whole length of the back of the house. Then, the water was spreading out under their patio, and seeping into the dirt from there, underground, until it collected in the lowest part of their back turf, about 25′ from the house…making a 10′ wide are of nothing but mush and mosquitos. Worst situation of condensate I have ever seen.
For sure, have the lettering face away from the point of view towards the unit. It looks a lot better/clean. Speaking of the lettering, I was taught when using primer, you know the PVC has been properly cleaned and primed when the lettering has been removed before you glue it… interesting on the 1/8″ slope. I’ve been told always go for 1/4″ per 12″ slope. I guess if I’m a little off/short on my 1/4″ per 12″ slope. I’ll still meet the 1/8″ per 12″ slope requirement.
Thank you for putting up this article. It was very informative. I am in southern California, so a lot of what you presented will apply (code wise). I am installing a 95% furnace. But I have a few questions. I cannot install my condensate into an existing sanitary drain. It’s just too much work. I will terminate it out the side of the house just like at 1:50. My house is pretty much the same as the one in your example, in that it is soil on the side; no slab. However, I read somewhere that if you don’t neutralize the acidic condensate that drips into the soil, that it could potentially damage the foundational slab to the house. Is that true, or just overkill? -Do I need to worry about neutralizing the condensate before it drips onto the soil? -And since the side of the house is soil, is there still a need to do a French drain? -My condensate termination will be about 7 to 8 ‘ (it’ll exit from the attic) from the soil. Is this permissible? I