TOPIC: Water Heaters

I recently inspected a fairly new nat. gas unit with a sealed burn chamber. Everything was working, but was wondering how these units get their combustion air. Also, the vent pipe was sloped slighly downward (3" over 3 feet) before it connected to the furnace venting which was properly sloped upward from that point. Anyone have any experience with these?

Frank - hard to imagine the venting without a picture but:

--  In my area shared venting is not appropriate unless the house is over 20-some years old.  Even then it is recommended for new installations that a separate vent into the chimney be involved.
--  If there is a hood over the heater, with a space for drafting, a 3" downward slope will kill a proper draw.  A down-slope would also encourage back-drafting from the furnace vent.  For me, 3" over 3' is not "slightly downward."  It sounds like they replaced an older, shorter unit with the one you see now, a few inches taller.  I think that a positive slope is necessary, even for a power-venting unit (although not the high-efficiency units with PVC vents).
--  As to the combustion chamber, there has to be a way to get in.  Your combustion air thought is right on, but also - how would the plumber light the pilot light or clean the burners when necessary?

What's the brand?  You should look up the installation specs or call a gas-certified plumber and ask him your questions.  I have a plumber friend I call all the time (once was about propane conversion kits, which are really tricky) and he has the answers for me off the top of his head.  It makes him feel good that I would call him too.  I also have contacts at the various of the local county inspection/permit offices and they are helpful too.  If you describe this to them and they feel it is a bad installation, they will make arrangements to go out and see it, condemn it, and you are off the hook, but smell very sweet.  The installer would be responsible for any corrections.

Also, on my report, I reserve the right to amend the report for three days.  That way, if I have questions that are not answered during the inspection, I can get the answer and fax and mail a bona fide and substantive letter.  I simply state that "this letter is a part of and in addition to the home inspection report of 21 August 2008."

Hope this helps!  Keep us informed as to what happens...

If I understand what you're describing, this is a concentric (tube in a tube) intake/  ventilation system. It takes its intake air from the same place that it is exhausted.

I don't think it can be concentric as it is "connected into the furnace vent which was properly sloped upward from that point."  You still might want to look up installation specs with the brand and model number.  I generally don't write that stuff down, nor does it appear on my report.  However, Frank, you should try to find out what you can about the unit.

Yea, I re-read that and I read wrong the first time.

??? Trying to post, my first time in here.