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venting a water heater through a wall???

16 years ago

Building a new house and trying to figure out my hot water. I have thought about tankless (and I still am), but I think I would much rather go with a regular tanked unit. It is me and my wife with 2 little ones. The house will have 1 shower, 1 soaker bath, 1 bath/shower combo, 3 lavs, 1 utility sink, 1 kitchen sink, and a dishwasher. We generally do not use hot water for clothes washing.

The water heater will go in the utility room on the first floor next to an outside wall. I do not want to vent up to the roof unless it can be done in a 2x6 wall.

I know of powervents but I hear they can be loud and troublesome.

What options do I have for water heaters that can be vented out a wall instead of out of the roof?

Comments (17)

  • mikeyvon
    Original Author
    16 years ago

    I see that a direct vent model may be the one to go with. Any reccomendations on models and sizes?

  • lazypup
    16 years ago

    All solid, liquid or gas fueled water heater, whether they are tank type or tankless must vent through the roof unless they are direct vent.

    The only other option is an electric water heater which requires no vent.

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  • jakethewonderdog
    16 years ago


    There are plenty of heaters that are designed for sidewall venting including powervent models, some that vent through PVC pipe. Most tankless heaters are also designed for sidewall venting.


    Most sidewall venting units include a draft inducing fan that may produce objectionable noise. That includes tankless models. How important is noise in this case? A power vent water heater will cost about the same as a tankless heater and avoiding a "through the roof" vent can make the difference in a tankless installation being affordable or not.

    Also, you need to be aware of combustion air intake requirements for any type of heater. Most Tankless units have a direct vent option.

    Don't know what part of the country you are in, but the tankless also offer an exterior mount that solves a number of problems including space, noise and venting.

  • jakethewonderdog
    16 years ago

    Hey Lazypup,

    I'm trying to get some clarification:

    What I understand to be "Direct Vent" are heaters that draw combustion air from the outside via a vent connection rather than from the surrounding room in which they are installed.

    I have seen normally aspirated direct vent heaters. I have also seen tankless heaters labeled direct vent that get combustion air from the outside and tankless that don't draw combustion air from the outside (same model, just one is direct vent and one isn't)

    There are also sidewall vent powervent units that don't pull combustion air from the outside.

    Does code have a different definition of "direct vent" than what is used by manufacturers?

    Sidewall venting tankless non-direct vent

    Sidewall venting direct vent tankless

    Here is a link that might be useful: Sidewall powervent

  • lazypup
    16 years ago

    In any combustion system if we increase the velocity of the airflow it results in a dramatic increase in combustion temperature.

    As the temperature in a vertical exhaust stack increases it results in an increased velocity of flow which in turn increases the velocity of incoming combustion air to the burner. To insure that the velocity of air in the combustion chamber does not go over a preset limit all standard water heaters are required to have a "Draft Hood" or a "barometric damper" that will allow relief air into the stack to regulate the velocity of flow in the stack.

    The inclusion of a draft hood or barometric damper defines it as an "indirect vent".

    Direct vent Tankless water heaters or high recovery tank type water heaters have combustion chambers generally made of stainless steel or other metals that will tolerate a much higher operating temperature range and they have a continues pipe from the combustion chamber to the flue with no provision for relief air. As the temperature in the stack increases the velocity of flow through the combustion chamber increases proportionally, thus creating a much hotter combustion.

    There are a number of problems associated with this type of draft control.
    1. On initial startup there is a delay until the stack reaches proper temperature to produce the necessary draft.
    2. They require a minimum vertical height of flue stack to insure the necessary draft.
    3. If the stack is too high there is excessive draft and the combustion temperatures could rise above acceptable limits.

    The solution to these problems is to add an "induced draft fan" which will immediately establish the correct velocity of flow and continue to regulate the velocity for the entire duration of the combustion.

    By using the fan to regulate the combustion air, some units then have a method of bypassing some air from the fan which is then injected into the flue on the exhaust side to regulate the final temperature of the exhaust gases. When there is enough induced relief air to limit the exhaust gas temperature below a preset limit they may then use PVC as the exhaust flue.

  • coolvt
    16 years ago

    A good education on the venting theory. I learned something. Appreciate it.

  • jakethewonderdog
    16 years ago

    But to answer my question, it sounds as if what the code considers to be a "direct vent" is different than what manufacturers are calling "direct vent".

    In practice, a standard tank type heater with a draft induction blower is considered a "power vent". These are sidewall venting heaters.

    While any heater that gets combustion air directly from the outside is typically called "direct vent".

    Thus according to manufacturers terminology, you have direct vent and standard (non-direct vent) tankless heaters. Direct and standard powervent heaters and direct vent normally aspirated heaters (they are sidewall vented and have a coaxial vent without a blower).

    And to answer the OP's question, he has the option of indoor tankless (w or w/o direct vent option, dep on application) Outdoor tankless, Powervent (again w or w/o direct vent) and a normally aspirated tank (commonly called a direct vent) that is designed for sidewall venting but has no blower.

    Or electric.

    Note that the energy factors on normally aspirated gas heaters is generally lower because the flue gas has to be hot enough to induce the draft. Whereas a powervent can reduce the flue temps (increasing efficiency) and a tankless can reduce the flue gas temps near the condensing point.

    Once near the condensing point, the flue materials must be able to withstand the acidic condensate. That's why tankless heaters must use stainless steel vent pipe and some powervent heaters use PVC.

  • lazypup
    16 years ago

    It has nothing to do with how the burner gets combustion air. The technical difference between a direct vent or indirect vent is determined by whether or not there is an atmospheric air inlet on the exhaust vent.

  • jakethewonderdog
    16 years ago


    1. You can vent through the sidewall with the appropriate heater. Be sure you understand what the restrictions are as far as vent placement.

    2. Decide if you are going tank or tankless. This is potentially a good application for tankless, esp if you are in a warm weather climate.

    3. If tank, your soaking tub will require a larger heater. How big is the tub? You will need at least a 50 gal tank.

    4.If tank, you can use a power vent unit (with a blower) or a non-power vent unit (what is often referred to as a "direct vent"). The noise of a blower was a concern for you.
    Power vent water heaters near tankless in cost.

    4. Direct vent is an option on many heaters. From the standpoint of manufacturers, Direct vent means that it has a connection to pull the combustion air from the outside. You may need this if your utility closet doesn't have enough free vent space, (in the doors, for example).

  • mikeyvon
    Original Author
    16 years ago

    Hey thanks for the responses.

    From what i can tell, I need a WH that vents through a sidewall, be it direct vent or powervent. I understand that the terminalogy can be argued, but I have come to understand (from the manufactures and from friends) it as jake described.

    1. I am checking on vent placement. I do have a a few small windows that are close by. I am waiting for a call back from the inspector.

    2. I am still undecided on a tanked or tankless. I am leaning towards tanked for simplicty reasons and due to the all the problems I have heard about tankless. I have others that really like thier tankless though. I am in the Mtns with cold incoming winter water temps. We are under about 1 foot of snow right now.

    3. We have not picked our final tub, but it will be a med sized soaker. If we go tanked, I will want a larger size. Our current rental has a 40 gal and the shower is not quite long enough for me.

    4. Noise is somewhat a concern for me. I have heard mutliple reports about powervents. Some say they are overly loud, others say it is acceptable. I just want to avoid overly loud. While price is always a concern, tankless and powervents fit my budget.

    5. If i go with a tanked unit, it will be in our utility room, which will require a vented door if it pulls air from inside. If I go tankless, idealy I will place it on the outside wall.

  • jakethewonderdog
    16 years ago


    Do some calculations just for grins and see if a tankless would work for you. A Rheem 74 will do 4.7 gpm at a 70 degree temp rise (35 degree inlet to 105 for a shower). There are some heaters that have a higher BTU input that will do a little more gpm if you need it. The Rheem is about $1200 with the vent kit and the valve kit. It would save you about 41% in fuel costs over a tank and you would get a tax credit.

    The only tankless units that had problems that I'm aware of were the Bosch units that used the water to power the ignition. Very lame. I think there were other people, particularly with electric units, that worked properly but weren't sized properly.

    If it were me, the choice would be between the normally aspirated sidewall vented (commonly called direct vent) tank heater or the tankless. The largest direct vent tank heater I normally see is 50 gal and they have crappy energy factors (in the high 50's). I think you will find them for around $700.

    The powervent costs about $1200 bucks for a 50 gal and are about as complicated as the tankless and about as noisy. I think the early models were more noisy that later ones.

    If you can purchase a tankless that will serve your needs for between $1200-1400, including the vent kit, and you have adequate gas service to the home, you will pay back the additional cost of the tankless over the direct vent tank heater in less than 5 years assuming you save $120 a year and take advantage of the $300 tax credit.

    The Rheem tankless has an energy factor of .82 while the Rheem direct vent 50 gal has an energy factor of .58 That's a 41% improvement and would easily net $10 a month difference in energy savings.

    If you go with the direct vent tank, it will pull air from the outside. If you go with a tankless, I would get the direct vent option so that you don't have to worry about venting the utility room (and letting the noise into the rest of the house).

    BTW: Page 12 and 13 of the link below do a good job of explaining the restrictions on side vents. Of course check with your inspector, but if you are looking for guidelines, these are pretty good.

    Here is a link that might be useful: Installation manual for tankless side venting

  • tommmy2007
    16 years ago

    I bought the Bosch which is called the problem unit in the above post for several reasons .Price for one,I wanted the 300 $ tax rebate,And I wanted it to work if the eletricity went off (I live downtown in a major city but I lost power for 4 days not long ago). So this forced me due to the rebate to get one without a pilot light. It has the 5 inch vent pipe which I do not like.Having a 5 inch vent running out my roof during winter I can not see how that is energy efficent. The screen filter did need to be cleaned several times to make the heater fire off correct ( I installed the unit myself and knocked debris loose reducing flow to hydrogenerator keeping the ignition from lighting ).So if a service call would have been involved (probably at least 12 hours response and no telling what it would cost me) there starts the problem with the Bosch systems and you probably would have had to make a second service call to get it all.I did it myself a 15 min job max . The vent pipe need valve to open when the heater fires up but that requires eletricity.I considered a outdoor one but how do you keep it from freezing seems it need some sort of heater and if so does it qualify for the rebates and I guess it would need eletricity to work. So what happens if the eletricity went off on a freezing winter day . I noticed the through the wall vents for Bosch were stainless adding about 300$ in vent pipe.The prices of through the wall vent systems heaters is that including install and are they getting the full 300$ tax rebate in 2008 .

  • svejkovat
    11 years ago

    Can I add a couple of questions here that pertain to the OPs questions as well as my own?

    I'm also near the bottom of this learning curve and want to replace my 25 year old nat gas 40 gal water heater.

    The OP mentions the co-axial venting as a quieter option since it has no fan. I asked the same thing of a local contractor last week here to give me a furnace estimate. He said that all coaxial units do in fact have fan induction.
    True or no?

    Also, the ideal installation for a through-roof water heater, standard non-induced draft, it ventilated through an existing chimney. Correct? It would be a two hour job for me to simply extend electric and plumbing to place the water heater ......right now it's next to the washing machine against an external wall..... next to the furnace and out the chimney.

    Lastly..... If it's only a matter of induced draft from the length of the shaft of vertical rising hot exhaust, why couldn't a "regular" water heater exit an external wall with into a tall stand pipe that rises to just below the crest of the roof? Would not work for all, but my water heater is in the rear of the home and faces a tall stand of trees. The pipe would look fine, and it would be pretty inexpensive.

    This post was edited by svejkovat on Wed, Feb 20, 13 at 9:26

  • weedmeister
    11 years ago

    Any particular reason you chose to resurrect a 5 year old thread rather than start your own?

  • kc270
    11 years ago

    Svejkovat - check the direct vent style water heaters on the websites of Bradford White or AO Smith, two major water heater manufacturers. Those units have co-axial venting and do not have fans.

  • TallMinnesota
    10 years ago

    I have an A.O.Smith PGCG 50-248 water heater which currently is vented many feet up through a two story high roof. I have the option of venting 10 feet out the basement under a deck and if necessary 8 to the outside of the deck. Is this advisable as it is very close to the outside wall.