Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

concentric termination relative to dryer vent

njbilltnjbillt Member Posts: 30
The manual just says to avoid terminating near a dryer vent, but it doesn't say what they consider "near." Any input or experience here would be appreciated. I have few choices for this termination.


  • SWEISWEI Member Posts: 7,356
    Whose vent?

    Every I & O manual I have seen is quite clear on the specifics.
  • SnowmeltSnowmelt Member Posts: 1,195

    The corner on other side of house
  • njbilltnjbillt Member Posts: 30
    Why? What happens?

    You did read I have limited choices here?
  • njbilltnjbillt Member Posts: 30
    It's a Rheem condensing tank

    Actually it doesn't. This is why I ask.
  • HenryHenry Member Posts: 968
    Air inlets

    In Canada we have B149.1 that addresses the situation of an combustion air inlet and a dryer or other vents. If you want to block the burner with lint or corrode the heat exchanger and burner, install it within 10 feet. I can garantee that the appliance will not last very long.
  • icesailoricesailor Member Posts: 7,265

    Canada is way ahead of the southern tier than Southerners want to admit. If you see a Sea Change in something in Canada, it will be in the US, sooner or later.
  • njbilltnjbillt Member Posts: 30
    well then ...

    ... I guess I have to move the dryer vent. I'm not buying 10 feet though. That seems a bit extreme.
  • JackJack Member Posts: 1,044
    "Not buying 10'"

    On a dryer vent 10 ft is a minimum. Arbitrarily moving the dryer vent will likely affect the performance of the dryer. Once you start adding 90's to a dryer vent the performance falls off. If you move it I would strongly suggest using AL pipe, not flex, to reduce the pressure drop. The boiler likely has more range vent wise and may be the better choice to move.

    Not buying it and leaving it may be ok. Then again, it may become your biggest nightmare. It can certainly become your customers biggest nightmare. You have to see a couple of appliances that are affected by a dryer to believe how far away you WANT to separate the vents
  • SnowmeltSnowmelt Member Posts: 1,195

    Don't run the dryer the same time you run the a/c.

    Put a lint trap outside the house..

    Over all it's not the end of the world, I have a few costumers that I clean the coil off every year.
  • RobGRobG Member Posts: 1,850

    Vent? concentric vent? A/C? Once again Snowmelt, you make no sense.
  • njbilltnjbillt Member Posts: 30
    Yeah I didn't get that either

    We got a little sidetracked here. It's a power vent condensing tank water heater. Not a furnace or air conditioner. Not running them at the same time is unlikely though because if I'm doing laundry, I need hot water. The fact that this intake is for a water heater I think is important. It's not going to run as often as a furnace. Still looking for advice on this. I understand we don't want lint sucking into the heater intake, but I've been here for 20 years and the lint trap on the dryer gets all the lint. it's not like the exhaust from the dryer is getting directly routed into the intake of the water heater. What about tree litter? I've never read anything about the placement of an intake relative to things that can fall from trees. When you think about it, there is all kinds of stuff floating in the air outside.
  • njbilltnjbillt Member Posts: 30
    thank you for the constructive reply

    We got a little sidetracked here though. It's not a furnace, it's a power vent water heater, which adds to my problem. if I'm doing laundry, I'll need hot water. They most likely would run at the same time or at least overlap.
  • RobGRobG Member Posts: 1,850
    It's not

    It's not just the lint, there is water vapor containing waterever chemicals are in the water. Chlorides will kill a gas heating appliance, dryer sheets contain all sorts of stuff as well. You really shoulld get the dryer vent as far away as you can.

  • njbilltnjbillt Member Posts: 30
    and my pool?

    and my pool is on the other side of the house evaporating gallons of water a day, and by the way, it's a salt water / choline generating pool. Which would be worse? it's a rhetorical question but I ask it to make the point. There are worse thing in the enviroment 100% of the time. Is a dryer vent that may run .5% of the time that the water heater is drafting in it's exaust really that big of a deal?
  • icesailoricesailor Member Posts: 7,265
    edited June 2014
    Mod Con's & Salt Water:

    If you have a Mod Con boiler that can suck chloride laden atmosphere, and it fails under warranty, don't tell the manufacturer that the pool is there. Many of them now tell upi to take combustion air from inside the envelope. You would not believe what a 5 year old Mod Con looks like after 5 years that is next to the sea shore.

    If you take the cover off, and the exposed aluminum inside the Mod Con is white and powdery, you have either cross contamination, high chlorides in the exhaust or both. Neither a good thing.
  • njbilltnjbillt Member Posts: 30
    the pool was rhetorical but

    I'm trying to separate the facts from the BS about the distance between a dryer vent and the intake for a condensing water heater. The book really doesn't specify. One guy up there who replied wanted them in different time zones, I'm sure just to be safe. Another is talking about an air conditioner.

    So, I have 2 concentrics for my 2 furnaces 18" apart, why can't the concentric for the water heater be within 18" of a dryer vent? The exhaust coming out of another condensing unit has to be more caustic than evaporated water and dryer sheets. no?
  • RobGRobG Member Posts: 1,850

    Actually, it was the same moron who recommended the different time zone and the A/C venting. If it is not specified in the manual, the simple answer is to call tech support at Rheem. They will be able to tell you what the minimums are.

  • njbilltnjbillt Member Posts: 30
    I called Rheem

    12 inches. That's it. 12 inches. And this is from an engineer. I also posed some of my other concerns, like tree litter. He said the lint and tree litter would just blow right through. If it got combusted, as ash, otherwise it would come out the way it went in. He said it would have to be a big blob all at once to clog the intake. He also didn't see a problem with humidity or evaporated clothes detergent or dryer sheet gasses. So now we know.

    Thank you all for your participation.
  • RobGRobG Member Posts: 1,850
    Get it

    Get it in writing. The inspector may want it in writing. I hate it when a project gets held up over a question. I would still keep it as far away as possible. I have seen lint and chlorine do terrible things.


  • Harvey RamerHarvey Ramer Member Posts: 2,214
    edited June 2014
    Rob is giving you some good advice.

    I would assume you want this thing to last as long as possible. Get chlorine vapor going through a combustion chamber, you get some particularly nasty stuff coming out the other end.

    Engineers are smart people but some of them have not familiarized themselves with the harsh realities one encounters in the field. The water vapour coming out of the dryer vent will be lighter than the surrounding air, hence it will rise. I think if you are 10' away on the same horizontal plane, that should be sufficient.

    Ramer Mechanical
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • njbilltnjbillt Member Posts: 30
    chlorine vapor

    Is this because I mentioned a pool in an earlier post? or because we wash our clothes in chlorine? Because the pool is on the other side of the building. That isn't a factor. The only thing I was asking about was the dryer exhaust vent. I think we're splitting hairs here guys. It's not like what's coming out of the dryer is the only thing going into the intake. It's not like the dryer is running every time while the water heater is running. And it's not like what's coming out of the dryer is acrid air. It is for the most part PH balanced water vapor. How bad can it be? As for getting it in writing for the building inspector, there is no code for this. I already knew this. That's why I asked. My solution will be to move the dryer vent a little, with a new vent that shoots the exhaust away from the intake of the water heater. I will be about twice as far as the minimum they allow. Will the water heater draw in some of the dryer exhaust once in a while? Yes. But it's not a perfect world. I'm comfortable with this solution.
  • Harvey RamerHarvey Ramer Member Posts: 2,214
    Sounds like you have the answer, but

    Pool and laundry products and common household and hobby products often contain fluorine or chlorine compounds. When these chemicals pass through the burner and vent system, they can form strong acids. These acids can create corrosion of the heat exchanger, burner components and vent system, causing serious damage and presenting a possible threat of flue gas spillage or water leakage into the surrounding area.

    Potential contaminating products

    - Spray cans containing chloro/fluorocarbons

    - Permanent Wave Solutions

    - Chlorinated wax

    - Chlorine - based swimming pool chemicals

    / cleaners

    - Calcium Chloride used for thawing ice

    - Sodium Chloride used for water softening

    - Refrigerant leaks

    - Paint or varnish removers

    - Hydrochloric acid / muriatic acid

    - Cements and glues

    - Antistatic fabric softeners used in

    clothes dryers

    - Chlorine-type bleaches, detergents, and

    cleaning solvents found in household

    laundry rooms

    - Adhesives used to fasten building products

    and other similar products

    Good Luck

    Ramer Mechanical
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • icesailoricesailor Member Posts: 7,265
    Passed Gas:

    Whenever I have to pass gas in public, I always try to be polite and aim it away from potentially offended intakes. Depending on conditions, some are overcome with the smell. It doesn't happen every day. Or every month. But there are times.

    Other times, it just doesn't matter.
  • njbilltnjbillt Member Posts: 30
    What you say is true ...

    ... but are these things getting into every ones heater, or just mine because I asked a question? While I agree all these things would be bad for a combustion chamber, I doubt the proportions would be significant enough to shortened the life of this water heater by more than a day or 2 just because it "may" draw in some exhaust from a clothes dryer once in a while. I ask questions in forums like this all the time because I respect advice from professionals, but every once in a while I'll get someone who analyzes the question down to absolute minutia, and the question ends up being antagonized rather than answered. If it was such a problem, there would be a strict code for it, and somebody could give me examples of such failures rather than suppositions. I've seen neither. I'll get them as far apart as I can, which will be about 2 and a half feet. I believe this is good enough.
  • icesailoricesailor Member Posts: 7,265

    I'm an American, who worked in the USA. I developed a deep respect for Canadian Codes because they seem to have a better method of protecting the public from unsafe equipment and practices. Like when something like the early plastic venting went bad, it was Canada that outlawed it first. It took a lot of "push" to overcome the powers of manufacturers and their lobbyists to get it taken off the market in  the USA. The UL listing in the USA is a joke. If you are willing to pay enough to get one, you get one. No matter how dangerous your equipment is. When I see the CSA sign, I at least think that someone has my best interest and my customers at heart. If Henry or someone from Canada says that something needs more separation, I just figure that someone died or got sick and there's a good reason behind it.

    There isn't a single PCV pipe and fitting manufacturer that advertises that their products are approved by them for gas venting exhaust that is over 140 degrees. Judging from all the white PVC pipe and fittings that have turned brown that I saw, I'm guessing that there is a lot of overheated pipe.

    Its bad enough that improper things are done from a lack of knowledge. Its worse when someone who should know better does it anyway.

    I personally spent years trying to install plumbing and heating in houses where some designer or architect made a conscience decision to design my work out of the building. In other words, a house that could have no plumbing or heating. Because a light fixture location was more important than a toilet or tub location.Sometimes, you have to tell the designer, here are your options. They aren't mine. They're YOURS.  You figure it out. Their bad planning doesn't constitute an emergency on my part.

    Somewhere. I saw photos of a Canadian apartment building where they were forced to put concrete filled pipes concreted into the ground to protect the gas exhaust terminations from being smashed by parking cars. When I saw that, I thought, how thoughtful. Someone doesn't want someone to die. And they went to some gymnastics to get the terminations above the snow lines too..

    That impressed me.

    Judging from the amount of lint I find on the ground around my dryer vent, dryer lint filters are a joke. Another Oxymoron.
  • RobGRobG Member Posts: 1,850
    edited June 2014

    Ice, obviously you don't buy the "lint free" clothing like everybody else in the world. You must get the stuff made in India or China.

    It sounds like the "Perfect Storm", dryer vent, concentric vent and a few well placed shrubs to hide them all.
  • SWEISWEI Member Posts: 7,356
    Concentric vents

    are a solution of last resort for me.  A wall intake with a roof vent is the go-to solution whenever possible.
  • icesailoricesailor Member Posts: 7,265

    All my clothes are "lint free". Even my Wear Guard pants and Lands End Tee Shirts. All made somewhere except the USA. And no matter how old they get, I still find lint in the dryer lint trap. And every now and them, I have to clean the lint from the vent outlet damper that keeps the mice and birds out.

    Then, there's the white plastic dryer vent that they sell like candy wherever you go. The stuff that you aren't supposed to use. I always hard pipe dryers with the solid flexible aluminum pipe for odd turns. I always use that bullet proof aluminum tape (the stuff that some use for covering rust holes in auto bodies) to hold the lengths together with an occasional pop-rivet.

    Someone told me once that I should use zip screws like he did. It won't ever fall apart. And it's easier to get apart than with the messy bullet proof tape. It was the guy who vented the gas dryer I was going to connect. He helped me out a lot. He forgot to convert it to LP from Nat. Gas. Oh, and be sure to always have the male part of the metal duct facing the dryer so it can catch any possible lint.
  • RobGRobG Member Posts: 1,850
    I hope

    I hope you knew I was being sarcastic, lint free clothes? Concentric vent, shrubs? In the words of ME "I'll be here all week"
  • icesailoricesailor Member Posts: 7,265
    Dryer vent lint:

    My Snark Switch is on a rheostat. You never know where it is set to.

    I wish that someone hadn't mistaken my camera case for a fanny pack when I was in Lowe's. I had some really nice venting situations on the memory card.

    One being how well Concentric Vents work when you hide them with decorative grass that grows up 4' in a season. How well it improves 90+ gas furnace's efficiency through the secondary heat exchanger.
  • njbilltnjbillt Member Posts: 30
    so now...

    so now concentric vents are no good no matter where you use them?
  • icesailoricesailor Member Posts: 7,265
    Concentric Vents:

    I personally haven't seen the problems that everyone squawks about. And they can be used in a vertical position through a roof. Where I worked, at some time, the wind would blow from any point of the compass. As long as you don't allow the landscapers to plant trees and bushes in front of them, or the owner designer just hates the sight of them and finds some antique cast iron screen and has it installed 2" in front of the outlet, they work fine.

    If the normal highest snow level is 27", and you must keep the termination a minimum of 12" above the snow line (39"), and you want to have the vent termination through the rim joist that is less than 16" off the ground grade, its really hard to use a concentric.
  • njbilltnjbillt Member Posts: 30
    in writing?

    You pose this as though the Rheem engineers said I could do it off code. There is no code. If there was, I wouldn't be asking. You should all be honored I asked you guys instead of the building inspector, although a few answers were as antagonizing. He probably would have wanted it around the corner too.
  • RobGRobG Member Posts: 1,850

    Whenever I deal with an issue that Is not covered in the installation manual I always try to cover my but as best I can. If an engineer from the factory told you something, just have him put it in an e-mail so that if an inspector asks or a warranty issue comes up you have it covered.

  • j a_2j a_2 Member Posts: 1,796
    power vent..

    Did you say this a power vent? If so why a concentric?
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!