Difference between conventional and FVIR gas water heaters

Difference between conventional and FVIR gas water heaters.

What are the visual differences?
How can you just look at it and tell the differences.
Images would be nice.

Thanks in advance.


The sealed chamber with a sight glass is the tell tale sign of an FVIR water heater



As a professional plumber, gas fitter and HVAC contractor, I am opposed to any nonqualified person working on a gas appliance. Gas can be unforgiving. A mistake can bring terrible consequences. With this in mind, if the view-port is dirty, preventing proper inspection of the combustion chamber, note what you can see and what you cannot see. I would discourage the home inspector from opening the inner door to clean the view-port glass or to peek inside.

Thank you.
However, I read that before I posted the question.

With conventional you can usually easily see the pilot and flame.

FVIR are sealed and only have a sight glass. You have to take panels off to light it with a match.

All the ones I see have a push button barbecue lighter thingy to light the pilot, no match required.

I don’t think they make one that you can light with a match, at least I can’t see how you could.