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@guzzinerd Said: Went over to a neighbor's who asked me to look at her water heater that isn't working. The code it's throwing is failed ignition so I told her she needs to call a professional

Good Call! If you have no Idea on what to do, then put your hands in your pockets and back away from the problem until you can find out more about it

@guzzinerd Said: While looking it over I noticed that the intake is tied into the exhaust pipe near the inside wall.. shouldn't they be separate?

What you are looking at is a proper concentric design venting system. Here is the detail on that design.

THE EXHAUST GASSES FROM THE HEATER WILL EXIT IN THE CENTER (Orange) VENT PIPE THAT GOES FULL SIZE 2" THRU THE MIDDLE OF THE ASSEMBLY. THE AIR INTAKE COMES IN THRU THE LARGER OUTER PIPE (Blue) THAT IS AROUND THE EXHAUST PIPE. THIS IS CALLED A CONCENTRIC VENT. YOU CAN MAKE ONE LARGER HOLE IN THE SIDE OF THE BUILDING AND HAVE BOTH INTAKE AND EXHAUST USE THE SAME OPENING.  SINCE THE INLET AIR COMES FROM NEAR THE BUILDING AND THE EXHAUST IS PUSHED STRAIT AWAY FROM THE BUILDING, THERE IS LESS CHANCE FOR THE EXHAUST TO FIND ITS WAY BACK TO THE AIR INTAKE.

@guzzinerd Said: She does have hydronic heated floors using a separate heater in the basement.

That is the wrong heater for a closed system. But that does not means someone mIght not try to make it work. I have used a water heater to do space heating and learned the hard way that Cheap isn't always the lowest cost way to do things. Ask Me how I Know?

@guzzinerd commented on @kcopp's statement: "Often that is called a "bazooka" termination. The piping most prob does not combine there… just the penetration." Only one pipe comes out of the exterior. Are you saying it should be divided from that point to the outside?

See my reply above about the Concentric. And I never heard it called a Bazooka.

@guzzinerd Said: Below the other water heater, this is what's running the hydraunic floor heat. The other water heater that's not firing right now is for the shower and sinks, residential.

There are parts on the potable water system that have no reason to be there. I can see that the owner of this location is not afraid of using unqualified and incompetent people to save $$. Those inexperienced people often charge less because they really don't know what they are doing. I would not offer any guidance @guzzinerd . Your inexperience may come back to haunt you if you get involved.