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Need Clarification on Mechanical Room Floor Drain Venting

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RichInKY

Registered User
Joined
Dec 19, 2023
Messages
7
Location
KY/TN
Hello, planning a new home with a basement mechanical room, in which I would like to have an "emergency" floor drain. The mechanical room will also have a domestic water heater and a condensing HVAC furnace, which I presume will need some way of collecting and discharging of the water. Additionally, the mechanical equipment will include a Lochinvar Indirect hot water system for whole house radiant floor heat. So I believe a floor drain would the solution to collect condensate from the equipment described above.

I am not finding any reference to this in any of the codes... Outside of ICC-901 which requires traps to be vented? Would a 2" floor drain with integral trap and back-flow device (as in the 2" PVC Integral Trap Floor Drain w/ Backwater Device -- like a Sioux Chief 802) be what I should consider, and will it be code compliant and NOT require a vertical vent?

There just does not seem to be much information regarding floor drains (and a venting requirement). The mechanical room floor drain would most probably be the lowest sewage connected device in the home. The sewage system will be a septic system with a dosing system requirement (pumped to the leaching field). The proposed floor drain will be part of the under-slab rough-in plumbing and connected to the main run that connect to the two chambered septic tank. The home will be located int Tennessee.
 
If you go to Table P3004.1 in the 2021 International Residential Code, it tells you that a floor drain takes "drain fixture units" and has a note saying that floor drains do not add hydraulic load to the plumbing system.

I recommend you go with a "combination vent" out of section P3111, - which basically means you run a 2" pipe to your floor drain and you don't have to vent it at all. The pipe is big enough to provide plenty of air to promote drainage without having a separate vent.

Combo venting can only be used for floor drains, sinks, lavatories, and drinking fountains, and they can only be used if you size them off the tables I showed here.
 
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Section P3008 requires backwater valves if the flood level rim is below the elevation of the next upstream manhole. Since you have septic, you probably need one since if something backs up it will probably come up through your floor drain first.
 
You're gonna need a trap and a trap primer. Traps are required by P3201.6, and a primer would be needed because of 3201.2.1.

Your condensate will keep the trap full during the summer, but in the winter you will need something to keep the trap full so you don't get sewer gas coming up into your house. There are a couple different ways to do this, I suggest you Google around to see the best method for your purposes.
 
Beniah Naylor said:
You're gonna need a trap and a trap primer. Traps are required by P3201.6, and a primer would be needed because of 3201.2.1.

Your condensate will keep the trap full during the summer, but in the winter you will need something to keep the trap full so you don't get sewer gas coming up into your house. There are a couple different ways to do this, I suggest you Google around to see the best method for your purposes.
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OK I searched and found this article which describes "trap-seal protection devices" and assume this is the option you are saying I could use in the winter months when condensation may be limited or non-existent. https://www.constructionspecifier.com/understanding-trap-seal-protection-devices/

However, since I will have the Lochinvar Unit running for the Radiant Floor Heat, I believe it will be a "condensing" unit as well? Which may preclude the need for a trap seal? I will continue to dig into this, but my perhaps final thing on this part -- is...can the condensate lines (either PVC clear hose or small pipes) be run to the rim of the floor drain for their individual equipment drainage purposes?

Thank you so very much for the great help! RichInKy
 
Beniah Naylor said:
You're gonna need a trap and a trap primer. Traps are required by P3201.6, and a primer would be needed because of 3201.2.1.

Your condensate will keep the trap full during the summer, but in the winter you will need something to keep the trap full so you don't get sewer gas coming up into your house. There are a couple different ways to do this, I suggest you Google around to see the best method for your purposes.
Click to expand...
OK --- As far as a "trap primer" ---- Using the code you referenced, I believe this could be accomplished by following ICC P3201.1.1 "Potable Water-Supplied Trap Seal Primer Valve" by having a line run from the "snack bar" sink, we will have which is located adjacent to the Mechanical Room -- Image attached. Is this what we could be permitted to do -- to provide an occasional supply of water to the floor drain trap? ("RED LINE" in the sketch below)TRAP.jpg
 
Beniah Naylor said:
Section P3008 requires backwater valves if the flood level rim is below the elevation of the next upstream manhole. Since you have septic, you probably need one since if something backs up it will probably come up through your floor drain first.
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Ok here is the Floor Drain I plan on specifying for the mechanical room (concrete basement floor) Note: Most likely it will be the WHITE PVC and not the ABS.Sioux Chief Intregal Floor Drain.jpg
 
RichInKY said:
However, since I will have the Lochinvar Unit running for the Radiant Floor Heat, I believe it will be a "condensing" unit as well? Which may preclude the need for a trap seal? I will continue to dig into this, but my perhaps final thing on this part -- is...can the condensate lines (either PVC clear hose or small pipes) be run to the rim of the floor drain for their individual equipment drainage purposes?
Click to expand...
I don't know if you would produce enough condensate with the Lochinvar unit in the winter to keep the trap full - there is much less moisture in the air to condense during the winter, and because the air is so dry, it will dry out your trap faster. Maybe you can, I don't know. Condensate lines can be run to the rim of a floor drain with no problems. Condensate lines don't create backsiphonage, so they don't even need to be air-gapped from the floor drain.
RichInKY said:
OK --- As far as a "trap primer" ---- Using the code you referenced, I believe this could be accomplished by following ICC P3201.1.1 "Potable Water-Supplied Trap Seal Primer Valve" by having a line run from the "snack bar" sink, we will have which is located adjacent to the Mechanical Room -- Image attached. Is this what we could be permitted to do -- to provide an occasional supply of water to the floor drain trap? ("RED LINE" in the sketch below)
Click to expand...
That would work for me, I think that is a good solution.

That trap should work, as long as you figure out how to attach the trap primer.
 
All gas appliances condensate when running.
A general rule of thumb, one gallon of condensate is produced for every 100,000 BTUs of input providing the appliance is operating in full condensing mode. A trap primer should not be needed since you will have condensing appliances running year-round.

There is an issue with the condensate within the flue that will produce acidic products that may be harmful to your plumbing system and or septic system when discharged there.

FYI: I have radiant floor heat in my basement and the trap in the shower will not dry out if the shower is not used all winter long. October through the end of May.
 
mtlogcabin said:
All gas appliances condensate when running.
A general rule of thumb, one gallon of condensate is produced for every 100,000 BTUs of input providing the appliance is operating in full condensing mode. A trap primer should not be needed since you will have condensing appliances running year-round.

There is an issue with the condensate within the flue that will produce acidic products that may be harmful to your plumbing system and or septic system when discharged there.

FYI: I have radiant floor heat in my basement and the trap in the shower will not dry out if the shower is not used all winter long. October through the end of May.
Click to expand...
Well yes --- I will have a gas HVAC furnace along with the Lochinvar Boiler for the Radiant (whole house --Warmboard® system) which will be a GAS Boiler. That being said, if the Acidic Flue Condensate would be a problem for the Septic System, I will just find an alternative, like having it be discharged to the exterior of the basement onto the landscape.

It is good to hear that the trap you mention does not dry out with limited or no use for a few months on end. I have read that there are things you can add to the water in a trap to slow the evaporation like using a small amount mineral oil. So I think my trap arrangement with having a connection to the Snack bar Sink will be doable? Either way --- The AHJ (authority having jurisdiction) will be the final input I will seek answers from, and I will seek them out before any work on the rough in is begun. Thanks again for your input!

PS: I also like the answer "Beniah" provided regarding the venting of the floor drain -- "I recommend you go with a "combination vent" out of section P3111, - which basically means you run a 2" pipe to your floor drain and you don't have to vent it at all. The pipe is big enough to provide plenty of air to promote drainage without having a separate vent" As that answered my initial inquiry on what to do about venting the basement floor drain in the mechanical room.

Thank you both very much, RichInKY
 
You can do a goggle search and find filtration devices you can install in the condensate drain line prior to disposing of the condensate into a drainage system.
Below is where the code definition of clear-water waste as it relates to septic systems. As always check with the AHJ that regulates and permits septic installations in your area with regards to any restrictions on condensate discharge from gas fire equipment into a septic system.

International Private Sewage Disposal Code®
CLEAR-WATER WASTES. Cooling water and condensate drainage from refrigeration compressors and air-conditioning equipment, water used for equipment chilling purposes, liquid having no impurities or where impurities have been reduced below a minimum concentration considered harmful, and cooled condensate from steam-heating systems or other equipment.

Recycling condensates from heating and air conditioning systems | Sauermann group

sauermanngroup.com sauermanngroup.com

"It’s also a bad idea to dispose of acidic condensates in a septic tank because the acid will kill the bacteria that keep the system self-regulating. Pouring acidic condensates down the drain and into the sewer is less problematic: the condensates will dilute and become less acidic when they mix with other liquids, especially if they contain soap and detergent (which are alkaline, i.e. they have a pH value well above 7). Nevertheless, it’s generally advised to protect some types of sewer with a neutralisation cartridge (although there’s no legal requirement for households to do so)."
 
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