When a home inspector identifies backdrafting at a water heater, what should be done about it? It depends.
Was it really backdrafting?
First, you need to find out if the home inspector identified backdrafting or signs of backdrafting. These are two very different things. The most notorious sign of backdrafting is melted plastic at the draft hood. Water heaters come with small plastic sleeves at the water lines, and they will easily melt and deform when a water heater backdrafts.
Note how the melting only occurs on the sides that face the draft hood; this is a dead giveaway that water heater backdrafting caused the melting. But to be clear, this is not proof that the water heater was backdrafting during the home inspection. It’s only evidence that the water heater backdrafted at some point in its life.
When a home inspector finds this, they should say there were signs of previous backdrafting, but not that the water heater backdrafts. A home inspector should not say a water heater backdrafts… unless it backdrafts! That melting could have occurred a long time ago, and the cause of the melting may have already been fixed.
Definitive Evidence
A great way for a home inspector to get visual evidence of a water heater backdrafting is to hold their camera close to the draft hood so their camera lens fogs over. The photo will look like this:
Or the home inspector could hold a mirror up to the draft hood and let it fog up. I love that method. This is definitive evidence that the water heater backdrafts. The mirror pictured below is comically oversized, but you get the point.
Also, a video that shows air pushing out of the draft hood is definitive evidence. Even better yet if the camera lens fogs up and the water line is covered in condensation.
So now that I’ve made a clear distinction between backdrafting and signs of backdrafting, let’s talk about next steps.
What to do about signs of backdrafting
When a home inspector finds signs of previous backdrafting, they can recommend having a second person inspect the situation further or inspect it themselves and make a call based on their professional experience, assuming they’re qualified. Everyone on my team at Structure Tech falls into the second camp.
If a second person is called in to inspect the situation further, it will probably be a plumber or an HVAC contractor. Some of them are qualified to do this inspection, and some aren’t. If the person inspecting the water heater draft is qualified, they will create a worst-case scenario to test the draft. If you want to be sure that whoever is coming out to inspect the draft at the water heater is qualified, hire someone familiar with the Building Performance Institute’s (BPI) Combustion Safety Test Procedure For Vented Appliances.
As a home inspector, I don’t follow these standards exactly, but I understand them and I do most of the stuff on this list. We call this a worst-case scenario test. If the water heater doesn’t backdraft under these conditions, I have nothing to report. I’d mention there were signs of previous backdrafting, but I did a worst-case scenario test and the water heater drafted properly, so there is nothing that needs to be done. End of story.
What to do about backdrafting
If a home inspector
By the way, yes, that’s an illegal flexible connector on my water heater. It was there when I bought my house and I don’t have a problem with it.
While I think it’s a bit of an extreme measure, one way to make a natural draft water heater a little safer would be to have a spill switch installed at the draft hood. This is a fairly simple safety device that will shut off the water heater if backdrafting is detected. Here’s an example of such a beast: SSK3 Spill Switch Kit. According to Bruce Strandberg at BWS Heating & Air Conditioning, these devices would cost about $125 for an HVAC contractor to install. I haven’t seen one of these in many years, so I don’t have any great photos to share of an installed spill switch, but you can find a photo here: http://www.wheatandsons.com/recent-jobs/draft-spill-switch/
If this test procedure causes the water heater to backdraft, check out my blog post on why it’s happening and how to fix it.