Hi everyone,

   I am new at Home Performance and I am looking for some advise. I did a test in, where the water heater , washer and dryer, and fau is in a utility room in the house. It had 2 small vents for air and the water heater did not pass spillage during worst case. When I do the repairs what do I do first and how. Do I need to add more fresh air in that closet to help it vent, is that why it didn't pass ? Thanks for your replies


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As a best practice the water heater needs to be replaced - a natural draft one has no business being in todays houses & should be replaced with a sealed combustion unit.

Okay I get that but that is not what I have to deal with. I will tell the client, but what steps do I take to find if it is clogged or just not enough air or ...?

Not to sound harsh but, you bring in a licensed specialist - full stop, end of story. You need to remember that you are like a family doctor. Once a known or possible issue is spotted that goes beyond what they are trained or knowledgeable about they automatically refer you to a specialist. Sure your family doctor may know what the issue is & maybe even know how to fix it, but that doesn't mean that they are going to propose that they do open heart, brain surgery, etc... themselves.

In this case I would say you need to bring in a licensed HVAC tech. While a plumber may have installed it, & possibly ran the one vent, the issue is with proper drafting, venting, etc... and they would have more knowledge about that. This also applies to your answer to Bud's question below.

But what if it is just a bird's nest - you still should bring in a specialist to clear it, check for other issues & reassemble it back together properly. I have seen to many people try to clear an issue & get everything out... well so they thought... needless to say they have either still had a blockage problem, have come close to or had a fire with some of the loose items falling further down into the venting

Now back to the "this isn't what I have to deal with", well actually it is as they have a naturally vented appliance inside a house and it should be removed (it doesn't matter if it failed or not). That should always be your first suggestion and note as worst case testing, never really is.

Hi Judi,  I'm kind of thick, fau I assume is an air handling unit/furnace.  I hate abbreviations. but that's just me.  Anyway, if that is a gas furnace I would also be concerned about sufficient air for it.  Clarify before I get too far out on the wrong limb :).


FAU stands for forced air unit. I thought maybe it needed more air too, but I am not sure and would like to know the steps to find the problem.

Your top priority needs to be to deal with these combustion appliances.  Either replace them with direct vent or electrical appliances, or move them to a part of the house where you can vent them without cooling down the whole house.  Keep in mind also, solar hot water as a potential option.  As you air seal and insulate, your worst case is only going to get worse. Whether the water heater is not passing because of lack of air or because the appliance is not operating properly is beyond my knowledge from here.. 

In regards to your last sentence... is it a plumber who will know? if it is working correctly or if it needs more air

Judi, Welcome.. Just a couple of questions: Was the DHW flue sized properly as per NFPA requirements? 40,000 BTU DHW = 4" vent pipe size. BTU rating of DHW unit? Was the DHW tank vented jointly with the furnace or orphaned? Outside temperture? Weather conditions?  Category 1 induced draft or atmospheric or category 4 90% furnace? and how well off are your customers? Thanks, Matt

It is 40K DWH w/ 4 in pipe. It is not joined with the FAU temp out side was 72 and clear. Natural draft. The FAU 's output  39000, the DWH is 40000btu. I don't know if there is a clog in the pipe or if I need more make up air or do I have to move the unit outside. The FAU is mecanically assisted. What is the fix here?


Do you remember the draft number on the DHW? Must be a small house if running only 39000 btu furnace or you're down south or out west. Their both vented alone? Draft number on FAU?  Vented to masonry chimney or B vent straight thru roof? Sorry for all the questions....Sounds like a clog....Birdsnest maybe. Check with mirror and flashlight. Possible return air leak in CAZ? Does it go real negative when air handler turns on? What's your worst case #? Add freshAir 80 or 100 could help....



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