If you have a condensing furnace, all the condensates run back to the furnace to a condensate pump which pumps the water outside. If you have a boiler that is blowing out the relief valve, could be bad feeder valve, aquastat, expansion tank.
Why Does My Natural Gas Furnace Leak Out Of The Overflow Pipe?
You have To install PVC as drain pipes.... Because the water that comes out of the Natural gas Furnace is Acid.... So if you have PEX with metal jonction, the water will destroy the metal jonction and it will leak..
Mr.woilly
Mr.woilly