The part about what the water in the trap is called is " water column " or water weight to stop air from being sucked in very common in FL like the videos keep it up i'am a 20 yr tech industrial process ref and comm ref these vids are very helpful to the next gen
Sweet Video... That helps alot, I been having a hard to grasping the negative and positive pressures on air handlers I m been putting traps on air handlers just to make sure that water wouldn't go back in to the system. I seen videos of DR Z, putsome5tankonit, hackfree, and your videos about the importants on drain traps. I ll be sure to put on a second trap on the secondary drain. THX FOR THE VIDEO
- I know your job isn't easy Linus I just wish I had your job, or to be as far along with my business as you are in yours. My first video was your LAN boy case review and it's great to see how far you've come. Even though I don't know you personally I am proud that you've made it this far. I also hope to build my business and get as far as you have. And I'm using Squarespace to do my website off your recommendation. Once it's up I will send you a link. Love the video and i like the guest you had on the show lately.
Mike I appreciated this explanation video. I have a question (homeowner diy): I have a Trane and the handler is horizontal in garage. I keep having condensate overflow issues (bad...mildew on wiring and wetting insulation of cabinet et cetera.. a mess with garage soaked floor) And I've had unit under service by professional a/c techs but no one has offered a solution. I now note that my primary drain line doesn't have a trap until it reaches the exterior of outside wall (running through wall not under slab floor and back above ground) and my secondary has in place SS1 overflow switch. Is this the reason for my chronic issue; the whole cabinet is soaked with water (trap too far away; and should be as close to unit as possible) If so, they didn't install with equipment replacement a few years ago. Also, you could hit your head walking under suspended handler hanging from garage ceiling when passing underneath if trap were installed. I would appreciate a follow up with any further insight/guidance from you. Thank you for your time. Brooks p.s. based on your explanation I have a negative pressure system (blower draws air from return through refrigerant coil)
thanks for explaining the difference between positive and negative air handlers.i have a problem with one leaking condensation its the vertical type negative air handler.i made a larger p trap but still leaks.
If the coil is dirty or has crud packed down in the coils it may actually be dripping straight off the coil instead of running down the coil fins to the catch tray. Make sure you actually have the trap filled with water too before you start it up or it will likely just suck air and not build up enough water in the trap to do its job. With no water in the trap it pulls enough air through the drain pipe to keep most of it from draining and if it gets high enough in the tray the blower will pick it up like rain droplets flying towards the blower, leaking wherever. Worse if it overflows. Also make sure the thing isnt clogged between the pan and the trap (or further down for that matter) i usually slowly pour a gallon or two into the pan to make sure everything is draining outside and nothing is leaking.
Your video about negative pressure and condensation line with p-trap is something of a concern for my circumstances. My question is where should the vent be on condensation line with negative pressure. Should it be after the p-trap or before it?
Just what I've been looking for. Thanks but a question. Have a new unit 2 years old, Goodman, I live in Houston, high humidity, the unit started leaking g down the air intake, started drippi g small amou t but then. Now when the unit shuts off about 7 pm after running all day, because wife wants it at 74 during the daytime. When it turns off alot of water is coming down the air intake. We opened a hole at insulated intake to look at coils, and can't see anything leaking. But yet it still does. HElP if possible.
Thanks for your videos. I have a positive pressure down flow furnace/evaporator. It has a P trap and is draining water properly but seems to be blowing out the trap of water allowing air to flow through. How to resolve this? Do I need to build a deeper trap? The trap is about 2 inches tall on the shortest side and is made from 3/4 PVC tubing and connectors. The trap drains to outside the building so it is venting conditioned air into unconditioned space. I also don't want critters to be able to crawl up the pipes and into the evaporator box.
Hmm.. Kind of hard to trouble shoot that without actually seeing it. It sounds like the trap is just too small though for the positive pressure, you should be able to increase the size several inches and solve the problem. Dont forget to leave a bkowout/cleanout opening so that if it gets clogged the guys can blow it out. You should be able to look at google images to get an idea of what I mean. If you put it on the unit side top of the trap remember you have to put a riser tube out the top that is higher than the bottom of the drain pan or it will leak out the top when uncapped (dont glue a cap on it) ...umm... Wish i could post pics, lol. Heres a sample page... air-conditioning-hvac.knoji.com/how-to-properly-install-a-condensate-line-trap/
***** Just wanted to say thanks for the help - I built a longer trap and it seems to be working. Thanks for confirming my suspicion before spending money on parts I might not need.
I have a horizontal unit. Not sure if it's positive or negative air flow... but there's no secondary drain that I can see, the whole unit is sitting on 2 2x4s that are just laying in the drain pan... sitting in water. There is no vent or p trap on the gravity feed drain and we are having to vacuum the water out of the pan 4x a summer because the pan is filling up. We've tried sucking the drain from the bottom outside, but it only pulls out so much and the pan won't start draining... we can't access the drain hole in the pan easily to vacuum out from the drain in the attic. This unit is only 5 years old.
Okie dokie... Wow! Well it sounds like either you have a positive pressure system and the primary drain line is partially clogged and when it can't keep up, the excess gets dumped into the pan... Or you have a negative pressure system, and because there is no p-trap, instead of the water going down the drain when the system is running, the negative pressure from the unit keeps it from draining while the unit is running. When the unit reaches temp in the house and shuts off, then it drains, BUT if the unit has to run for a long time because it's hot outside and it pulls a lot more humidity out of the house, it will be holding more water in the unit than the pan, inside the unit, can hold. It will literally overflow the internal pan, soak into the insulation inside the unit and start filling up the case. When the unit shirts off the water will start dumping out everywhere, out the main drain, out the emergency overflow into the emergency pen underneath, and out of the cracks and corners of the unit and dropping into the pan. If the unit is only five years old and you are the original owners, you might be able to harass the company into fixing their bad installation. Let me be clear, the pan that your unit is sitting in IS the secondary/emergency drain pan! There are two ports coming out of the unit where pvc pipe should be attached, one Port is slightly lower than the other. The lower one should be piped and run straight outside, with a p-trap attached to it if it's a negative pressure system. The entire pvc line running outside should have a slightly downward slope to keep the water flowing, with no bows in it that would cause problems. The slightly higher Port should have a small but of pvc then an elbow aimed down into the emergency pan, with another piece of pvc to get it down close to the pan so it isn't splashing all over if it's used. Then the emergency pan has a drain line coming out of it going outside as well. TYPICALLY the ac unit is suspended by wide, solid metal straps (not that plumbing strap with holes in it) or maybe up on 2x6's, or professionally hung with allthread bolted thru rafters above into U channel steel beams that the unit sits on. Then the emergency pan is HUNG below the unit, with a slight tilt towards the side that the pvc drain hole comes out of it. So that it sheds as much water as possible when there is an emergency and it is used. If you don't have two drain lines tapped out of the unit then something is wrong! You had a HACK install the unit. If you are looking at the front side of the unit, looking at the section where the electrical goes in and the door screws on to the blower section, if the AC coil is in the Left side of it, then it's probably negative pressure. The blower is Pulling air through the coil from your return vent, then pushing it through the heat section which is in the electrical section, then out to your supply ducts. If there coil is on the right side of the blower section, then it's forcing air into the coil, creating positive pressure, which would push the water down there drain line. Regardless, you need to have someone come in and fix the mess! Otherwise your problems will get worse. Eventually the emergency pen will start to rust thru and you will wind up with your sheetrock ceiling caving in and a huge mess in the house. If the internal primary pan is being overflowed then eventually the bottom of the unit will rust out too! If it's a negative pressure unit then you HAVE to have a p-trap on the primary, AND on the secondary going into the emergency drain pan. I don't know how many units I've run across that they did the primary but not the secondary! If the primary line gets clogged up and it has to drain out the secondary and they don't trap it, then if the unit runs too long it overflows the internal pan and flood the inside of the unit. Worst case scenario is that the water gets to the electric section and bad things could happen, depending on the manufacturer and where they placed the electric components. Hope this helps and keep me updated, if you think about it! ... On second thought, don't call them back, get someone else! The emergency Port is slightly higher because it's normally NEVER used, unless the primary drain line gets clogged up.
Didn't know it was that complicated. I didn't even know there was such a thing as negative pressure systems. I live in Canada and every house has a basement and every furnace I've seen is vertical, upflow, positive pressure. I'm just an engineer though, not an HVAC tech :)
my air handler/fan coil/heat pump (in attic) has blower on RIGHT and evap coil on left facing the unit (from attic stairs). HORIZONTAL unit. The primary does NOT have a p trap. It goes 1/4 in grade down (sloped) outside the home -follows the line set. Assuming this is a POSITIVE air pressure system or Draw thru.?// Havent had any issues backup- clean line yearly- the coil is rusted in the corner near the primary drain accces point.
+Marcie M Hi Marcie! I started a reply earlier but was sidetracked with a show my wife was watching, heh, when I came back my tablet had shut off and deleted my text! Before I can tell you if its positive or negative pressure I'd have to know which side of the system the return duct is hooked up to and/or which side the supply ducts going to your vents is on. If the return duct is on the left, like: Return Duct/Coil/Blower+Heat Elements/Supply Ducts... Then its a Negative Pressure system because the blower is pulling the air through the coil. If the Supply Ducts are on the coil side like: Supply Ducts/Coil/Blower+Heat Elements/Return Duct... Then the blower is pushing the air through the coil to get in the house and its Positive Pressure. I've seen negative pressure systems that never overflowed because they didn't stay running long enough at any given time to accumulate enough water to overflow the pan. However if it ran long enough and pulled enough humidity out of the air then it obviously would. Hope this helps! Mike
I have a positive pressure system with a trap on the main drain and a secondary drain for backup. The system mostly drained from the secondary. I cleaned the system out twice and even had a Beautler come out and service it but the darn thing still pours out of the secondary. Any Ideas?
Michael Wright if the line and the trap are blown clean and there is no restriction there then that just leaves two other possibilities, either there is some trash blocking the primary right inside the coil case where the primary attached or the drain line isn't sloping downhill properly and the water just lays there.
I poured allot of water inside the handler and it comes out both primary and secondary. I'm wondering if it was installed incorrectly. I bought the house 3 years old and it had signs of pouring out the secondary even then. ie. rust stains on the side of the house where the secondary drain outlet is. Here are photos... The primary is on the left and has holes in the cap for vents. I'm not exactly sure if this is the primary side.Can you tell? 1drv.ms/f/s!Ag1uZzGdnvjmgc1pYc6gVBq9ftA3gA
unless the customer whines about a gurgling sound in their bathroom sink keeping them up at night and then you can put a trap on a positive pressure just to quite it down...
I have a negative pressure air handler, with the inlet of the trap 7" long and the outlet ot the trap 3" high, i have a cleanout pipe on the inlet side of the trap with a cap on it but no vent pipe on the outlet side of the trap and it still leaks water inside after the fan shuts off, any ideas?
Sorry, somehow I missed this one! Hmm.. Well I have two thoughts. The first is that you might have a bunch of crud built up in the coil tray that is causing you problems. Second possibility... Well a three inch height should be fine, but how is the slope? Check to make sure you have a downhill slope all the way to the sewer drop. Sometimes Ill find one in an attic that looks fine initially, but the sewer drop is on the other side of the attic and somewhere across the attic they have the line bowed between the hangars and it cant flow out. Im assuming youve checked to make sure the line isnt clogged? Its been a while, so youve probably sorted it out by now, what was the problem? Mike
It's funny how you say nothing about where the vent goes on a negative and/or positive pressure system. I find it very interesting that you say absolutely nothing about that..... . Unreal
What 'vent'?? You have air going into the coil, air coming out the other side of the coil and the condensate drain, and the emergency drain (if applicable), that's it. :)
High quality info, low quality video, but explanation clear. Thanks
Thank you for taking the time to teach. I'm a home inspector and these morsels of knowledge are invaluable.
thanks for the videos - very helpful in understanding how the condensate drain is supposed to work!
The part about what the water in the trap is called is " water column " or water weight to stop air from being sucked in very common in FL like the videos keep it up i'am a 20 yr tech industrial process ref and comm ref these vids are very helpful to the next gen
You've explained this so well, thank you kindly!
Sweet Video...
That helps alot, I been having a hard to grasping the negative and positive pressures on air handlers
I m been putting traps on air handlers just to make sure that water wouldn't go back in to the system. I seen videos of DR Z, putsome5tankonit, hackfree, and your videos about the importants on drain traps. I ll be sure to put on a second trap on the secondary drain.
THX FOR THE VIDEO
So you only need a trap when you have a negative pressure system. I did not know that. Good info.
- I know your job isn't easy Linus I just wish I had your job, or to be as far along with my business as you are in yours. My first video was your LAN boy case review and it's great to see how far you've come. Even though I don't know you personally I am proud that you've made it this far. I also hope to build my business and get as far as you have. And I'm using Squarespace to do my website off your recommendation. Once it's up I will send you a link. Love the video and i like the guest you had on the show lately.
Good job explaining ....much appreciated!
!
It begs the question: Why would AC makers even MAKE an negative pressure system ?!?!
Mike I appreciated this explanation video. I have a question (homeowner diy): I have a Trane and the handler is horizontal in garage. I keep having condensate overflow issues (bad...mildew on wiring and wetting insulation of cabinet et cetera.. a mess with garage soaked floor) And I've had unit under service by professional a/c techs but no one has offered a solution. I now note that my primary drain line doesn't have a trap until it reaches the exterior of outside wall (running through wall not under slab floor and back above ground) and my secondary has in place SS1 overflow switch. Is this the reason for my chronic issue; the whole cabinet is soaked with water (trap too far away; and should be as close to unit as possible) If so, they didn't install with equipment replacement a few years ago. Also, you could hit your head walking under suspended handler hanging from garage ceiling when passing underneath if trap were installed. I would appreciate a follow up with any further insight/guidance from you.
Thank you for your time. Brooks
p.s. based on your explanation I have a negative pressure system (blower draws air from return through refrigerant coil)
The same here
Check may be the drain is line is blocked, air tight the unit,
thanks for explaining the difference between positive and negative air handlers.i have a problem with one leaking condensation its the vertical type negative air handler.i made a larger p trap but still leaks.
If the coil is dirty or has crud packed down in the coils it may actually be dripping straight off the coil instead of running down the coil fins to the catch tray. Make sure you actually have the trap filled with water too before you start it up or it will likely just suck air and not build up enough water in the trap to do its job. With no water in the trap it pulls enough air through the drain pipe to keep most of it from draining and if it gets high enough in the tray the blower will pick it up like rain droplets flying towards the blower, leaking wherever. Worse if it overflows. Also make sure the thing isnt clogged between the pan and the trap (or further down for that matter) i usually slowly pour a gallon or two into the pan to make sure everything is draining outside and nothing is leaking.
Your video about negative pressure and condensation line with p-trap is something of a concern for my circumstances. My question is where should the vent be on condensation line with negative pressure. Should it be after the p-trap or before it?
It should be after otherwise will defeat the purpose of the p trap and should be left open.
Just what I've been looking for. Thanks but a question. Have a new unit 2 years old, Goodman, I live in Houston, high humidity, the unit started leaking g down the air intake, started drippi g small amou t but then. Now when the unit shuts off about 7 pm after running all day, because wife wants it at 74 during the daytime. When it turns off alot of water is coming down the air intake. We opened a hole at insulated intake to look at coils, and can't see anything leaking. But yet it still does. HElP if possible.
Thanks for your videos. I have a positive pressure down flow furnace/evaporator. It has a P trap and is draining water properly but seems to be blowing out the trap of water allowing air to flow through. How to resolve this? Do I need to build a deeper trap? The trap is about 2 inches tall on the shortest side and is made from 3/4 PVC tubing and connectors. The trap drains to outside the building so it is venting conditioned air into unconditioned space. I also don't want critters to be able to crawl up the pipes and into the evaporator box.
Hmm.. Kind of hard to trouble shoot that without actually seeing it. It sounds like the trap is just too small though for the positive pressure, you should be able to increase the size several inches and solve the problem. Dont forget to leave a bkowout/cleanout opening so that if it gets clogged the guys can blow it out. You should be able to look at google images to get an idea of what I mean.
If you put it on the unit side top of the trap remember you have to put a riser tube out the top that is higher than the bottom of the drain pan or it will leak out the top when uncapped (dont glue a cap on it)
...umm... Wish i could post pics, lol. Heres a sample page...
air-conditioning-hvac.knoji.com/how-to-properly-install-a-condensate-line-trap/
mikie2501 Thanks for the detailed reply. I suspected the same; I will rebuild the trap to be taller to contain more water.
***** Just wanted to say thanks for the help - I built a longer trap and it seems to be working. Thanks for confirming my suspicion before spending money on parts I might not need.
So do you need to install traps (primary and aux) on positive pressure air handlers?
you did not talk about down flow systems in the video, i assume the same rules apply?
thanks for doing this video
I have a horizontal unit. Not sure if it's positive or negative air flow... but there's no secondary drain that I can see, the whole unit is sitting on 2 2x4s that are just laying in the drain pan... sitting in water. There is no vent or p trap on the gravity feed drain and we are having to vacuum the water out of the pan 4x a summer because the pan is filling up. We've tried sucking the drain from the bottom outside, but it only pulls out so much and the pan won't start draining... we can't access the drain hole in the pan easily to vacuum out from the drain in the attic. This unit is only 5 years old.
Okie dokie... Wow! Well it sounds like either you have a positive pressure system and the primary drain line is partially clogged and when it can't keep up, the excess gets dumped into the pan... Or you have a negative pressure system, and because there is no p-trap, instead of the water going down the drain when the system is running, the negative pressure from the unit keeps it from draining while the unit is running.
When the unit reaches temp in the house and shuts off, then it drains, BUT if the unit has to run for a long time because it's hot outside and it pulls a lot more humidity out of the house, it will be holding more water in the unit than the pan, inside the unit, can hold. It will literally overflow the internal pan, soak into the insulation inside the unit and start filling up the case.
When the unit shirts off the water will start dumping out everywhere, out the main drain, out the emergency overflow into the emergency pen underneath, and out of the cracks and corners of the unit and dropping into the pan.
If the unit is only five years old and you are the original owners, you might be able to harass the company into fixing their bad installation.
Let me be clear, the pan that your unit is sitting in IS the secondary/emergency drain pan! There are two ports coming out of the unit where pvc pipe should be attached, one Port is slightly lower than the other. The lower one should be piped and run straight outside, with a p-trap attached to it if it's a negative pressure system. The entire pvc line running outside should have a slightly downward slope to keep the water flowing, with no bows in it that would cause problems.
The slightly higher Port should have a small but of pvc then an elbow aimed down into the emergency pan, with another piece of pvc to get it down close to the pan so it isn't splashing all over if it's used. Then the emergency pan has a drain line coming out of it going outside as well.
TYPICALLY the ac unit is suspended by wide, solid metal straps (not that plumbing strap with holes in it) or maybe up on 2x6's, or professionally hung with allthread bolted thru rafters above into U channel steel beams that the unit sits on.
Then the emergency pan is HUNG below the unit, with a slight tilt towards the side that the pvc drain hole comes out of it. So that it sheds as much water as possible when there is an emergency and it is used.
If you don't have two drain lines tapped out of the unit then something is wrong! You had a HACK install the unit. If you are looking at the front side of the unit, looking at the section where the electrical goes in and the door screws on to the blower section, if the AC coil is in the Left side of it, then it's probably negative pressure. The blower is Pulling air through the coil from your return vent, then pushing it through the heat section which is in the electrical section, then out to your supply ducts.
If there coil is on the right side of the blower section, then it's forcing air into the coil, creating positive pressure, which would push the water down there drain line.
Regardless, you need to have someone come in and fix the mess! Otherwise your problems will get worse. Eventually the emergency pen will start to rust thru and you will wind up with your sheetrock ceiling caving in and a huge mess in the house. If the internal primary pan is being overflowed then eventually the bottom of the unit will rust out too!
If it's a negative pressure unit then you HAVE to have a p-trap on the primary, AND on the secondary going into the emergency drain pan. I don't know how many units I've run across that they did the primary but not the secondary! If the primary line gets clogged up and it has to drain out the secondary and they don't trap it, then if the unit runs too long it overflows the internal pan and flood the inside of the unit.
Worst case scenario is that the water gets to the electric section and bad things could happen, depending on the manufacturer and where they placed the electric components.
Hope this helps and keep me updated, if you think about it! ... On second thought, don't call them back, get someone else!
The emergency Port is slightly higher because it's normally NEVER used, unless the primary drain line gets clogged up.
Didn't know it was that complicated. I didn't even know there was such a thing as negative pressure systems. I live in Canada and every house has a basement and every furnace I've seen is vertical, upflow, positive pressure.
I'm just an engineer though, not an HVAC tech :)
is there negative or positive air pressure in a handler box when sealed?
Thank you for the great video.
Great video, thanks!
How do you stop a negtve pressure in the winter when heater is on be side adding water sucking air in bathroom sink and yes it has a trap and a vent
my air handler/fan coil/heat pump (in attic) has blower on RIGHT and evap coil on left facing the unit (from attic stairs).
HORIZONTAL unit.
The primary does NOT have a p trap. It goes 1/4 in grade down (sloped) outside the home -follows the line set.
Assuming this is a POSITIVE air pressure system or Draw thru.?//
Havent had any issues backup- clean line yearly- the coil is rusted in the corner near the primary drain accces point.
+Marcie M Hi Marcie! I started a reply earlier but was sidetracked with a show my wife was watching, heh, when I came back my tablet had shut off and deleted my text!
Before I can tell you if its positive or negative pressure I'd have to know which side of the system the return duct is hooked up to and/or which side the supply ducts going to your vents is on.
If the return duct is on the left, like: Return Duct/Coil/Blower+Heat Elements/Supply Ducts... Then its a Negative Pressure system because the blower is pulling the air through the coil.
If the Supply Ducts are on the coil side like: Supply Ducts/Coil/Blower+Heat Elements/Return Duct... Then the blower is pushing the air through the coil to get in the house and its Positive Pressure.
I've seen negative pressure systems that never overflowed because they didn't stay running long enough at any given time to accumulate enough water to overflow the pan. However if it ran long enough and pulled enough humidity out of the air then it obviously would.
Hope this helps!
Mike
Which is best, a trap at the coil or outside; on a negative up flow system?
Addendum to above, negative on almost all MH electric furnaces with a-coil at top.
Nice. Thank you.
Help me get this right ,blower before coil positive ,blower after coil negitive . Right?
good stuff, thanks...
What happens if you add a trap to a positive pressure furnace? Does it cause issues?
Nope, no problem at all!
I have a positive pressure system with a trap on the main drain and a secondary drain for backup. The system mostly drained from the secondary. I cleaned the system out twice and even had a Beautler come out and service it but the darn thing still pours out of the secondary. Any Ideas?
Michael Wright if the line and the trap are blown clean and there is no restriction there then that just leaves two other possibilities, either there is some trash blocking the primary right inside the coil case where the primary attached or the drain line isn't sloping downhill properly and the water just lays there.
I'll check it out and get back to you
I poured allot of water inside the handler and it comes out both primary and secondary. I'm wondering if it was installed incorrectly. I bought the house 3 years old and it had signs of pouring out the secondary even then. ie. rust stains on the side of the house where the secondary drain outlet is. Here are photos... The primary is on the left and has holes in the cap for vents. I'm not exactly sure if this is the primary side.Can you tell? 1drv.ms/f/s!Ag1uZzGdnvjmgc1pYc6gVBq9ftA3gA
Remember this folks when working on mobile homes, almost all are negative pressure systems.
unless the customer whines about a gurgling sound in their bathroom sink keeping them up at night and then you can put a trap on a positive pressure just to quite it down...
That's not a secondary drain, that's the fresh air intake!...HA..HA..
It begs the question:
Why would AC makers even MAKE an negative pressure system ?!?!
I have a negative pressure air handler, with the inlet of the trap 7" long and the outlet ot the trap 3" high, i have a cleanout pipe on the inlet side of the trap with a cap on it but no vent pipe on the outlet side of the trap and it still leaks water inside after the fan shuts off, any ideas?
Sorry, somehow I missed this one! Hmm.. Well I have two thoughts. The first is that you might have a bunch of crud built up in the coil tray that is causing you problems. Second possibility... Well a three inch height should be fine, but how is the slope? Check to make sure you have a downhill slope all the way to the sewer drop. Sometimes Ill find one in an attic that looks fine initially, but the sewer drop is on the other side of the attic and somewhere across the attic they have the line bowed between the hangars and it cant flow out.
Im assuming youve checked to make sure the line isnt clogged?
Its been a while, so youve probably sorted it out by now, what was the problem?
Mike
It's funny how you say nothing about where the vent goes on a negative and/or positive pressure system. I find it very interesting that you say absolutely nothing about that..... . Unreal
What 'vent'?? You have air going into the coil, air coming out the other side of the coil and the condensate drain, and the emergency drain (if applicable), that's it. :)
@@mikie2501 I see vents on traps all the time. I'm confused. Thanks for replying. So no vent is necessary?