Rinnai Water heater vent

What’s wrong with this water heater vent? (yes, that’s furnace vent, not ductwork it’s venting into…) :wink:

That looks like AN INSTANT water heater to me if so I do not believe the exhaust flue is big enough for 200,000± BTUs that come from those heaters .
I do not like the reducing of the flue either . Did you see the manufactures directions .
Good catch and thanks for the picture . Roy Cooke . Royshomeinspection.com

I have yet to see one of these, not common to my area. My question is, can they be vented with pvc for gas and do they need a power vent. Do they make these in electric, I hope not. Plus, I have read that this system is not efficient with a lot of hot water use. My local community action/ hud funded programs frown upon the use of this water heater

Actually, this was an inspection I did a few months ago, and didn’t write up anything about the vent. I got an email from the buyer (now homeowner) asking for my opinion because their Home Warranty company has said the heater was vented improperly. The homeowner is suspicious of their motives, thinks they are just out to sell her extra services, and trusts me for good information, so I want to remain accurate and credible. I don’t mind admitting a mistake, but I want to be accurate and credible with my corrected statement.
I don’t think that white is pvc, but rather B vent. I think. I’m going to make a return visit Tues, so I’ll know for sure then.
I’m wondering if that doesn’t need to be a Y at the furnace flue connection, and if that’s really B vent on the heater, does it need to be B vent all the way out? From the pic, I’m not real sure if it drops a size or not. It may be connected to the inside of the B vent. The ‘duct’ tape looks loose at that point in the pic, so that could be the problem. It’s been a while, so my memory isn’t that clear on it. Had to do some digging just to come up with the pic. Just trying to be prepared when I go back.


I have some downloaded manuals of the continuum exterior model (Propane) if you need or you can sign up and download the proper tech manuals yourself at http://www.rinnai.us/members/login.asp

Let us know what you find out!

You beat me to it, I was going to tell Keith the same thing. The manufactures web site will have all the info on installation and maintanance of the unit, venting and all.:roll:

Tankless water heaters require special framing around the exhaust flue since the temperature is much higher. In this case, defer to the manufacturer’s recommended installation instructions. They are probably available online. I know for use that the Takagi is online.

Also, did you check on the gas line size? Tankless water heaters generally require a larger line size.

Though I cant see the “big picture” and the direction of gas flow in the bigger tapped vent, there apears to be a back flow issue?? Just a thought.

I agree. It sure looks like there needs to be a Y at the flue connection to help with backdrafting.

UPDATE: Seems this Home Warranty guy was real adamant about how bad that vent is, and told the homeowner if it was his he’d shut it off immediately, and go without hot water until it was fixed properly.
He told them there is a special high temp vent for those heaters that should go out through the wall, not into the furnace flue, and it’s about $900, which is what’s choking the homeowner. They think this guy is trying to oversell, and they’re calling me to verify (or not) that this is really necessary. I’m going to the Rinaii website next, and see what they have in the way of manuals.

Keith; I posted earlier that I thought these might need to be power vented to the exterior and I think PVC is OK, please let me know, I curious.

Also, if they can be power vented with PVC it’ good news because as long as you have access thru the rim joist it’s relatively inexpensive and easy to fix. Some power vents come with an air return so units can be installed in a small utility room and still breath and operate properly. Keep us posted,

The one I saw was stainless steel power vent.
Roy Cooke … Royshomeinspection.com

It is not okay.


vent pipe is very expensive to this system $90.00 for 3’ and is a PVC exterior with a heavy gauge aluminum center pipe…no other venting material can be used.


The ****** Rinnai link you posted does not work. Any Suggestions?**



Besides the vent being wrong, you need to check the gas meter to see if it can handle the the volume, IE> gas cloths dryer 35,000 BTU Furnace 100,000 BTU, Tankless water heater 165,000- 200,000, toal volume if all on at same time, 300,000 BTU (low side figure) most gas metere are 250,000- 275,000 BTU .

I followed Shawns link above, and downloaded the manual. It clearly states no other vent system can be used on these heaters. According to what the homeowner is telling me, Shawn’s right, it’s very expensive. They were told $900 for the thru-wall kit. Mfgr states that the vent cannot be shared with any other appliance, or free-flow vent system. (like furnace) So it’s power vented, but in this case makes it pricey, rather than simple and cheap, because it’s pvc exterior and alum interior. It’s going to be my problem however, when I have to 'fess up that I didn’t know that, and didn’t write it up during inspection.

Does it need to be power vented and why are these units different than a regular hot water heater or a furnace. Do they produce exhust hotter than a furnace?