How severe might the consequences be?

Wanted to get some HVAC expert opinions on how severe the possible consequences of the following issue may be.

1 year old home. NAtural Gas Furnace exhaust pipe through the roof with no cap. Because of some particulars in this case I am sure it has been this way since construction.

I see this from time to time. My theory is that this condition allows water to flow freely down the exhaust pipe and into the heat exchanger. Which could cause rust, shorten the life expectancy, etc. So I call out for not only repair to the problem but a thorough evaluation of the unit and heat exchanger by a licensed HVAC guy.

For my own information how detrimental is this? Will a year of this condition cause irreversible damage? Does the unit need to be replaced? Is it ok if an HVAC guy comes out and clears it?


what kind of furnace is it?

too many variables. The unit will need to have a more invasive inspection, put it into the hands of the Tech