Boiler heating both radiant heat and potable water.

I just inspected a home today that used the oil fired boiler as radiant home heat and also served as the only source of potable water heat. I have seen water tanks tied into the radiant heat boiler but never as the only source of water heating. Has anyone else ran into this? Are there any downsides or potential hazards o the setup?

If I had a picture I could give you a decent answer. I’m sure others will comment as well.

Thats common.
Some boiler manufacturers even have a domestic hot water coil built right into them.
Normally they would be providing 180 water as that is where a cast iron, if this is a cast iron section boiler, needs to fire.
Both the domestic (potable) at approx. 120 degrees and the radiant in floor heating which could be as low as 100 degrees would be mixed with cooler return water to be at a lower temperature.
If its baseboard radiant, that takes 180 degree water and domestic is only is mixed down to the 120 degree range.

If you can provide more details, I can get you a better answer.

Some times refereed to as a “Summer/Winter Hook Up”.