I bought a home a few months ago that had a Navien tankless water heater installed in 2019. Yesterday I noticed lots of water coming out of the condensate drain. The floor beneath the unit was a little wet too but whatever caused that bit of moisture has seemed to have stopped. But the water flowing out the condensate drain is continuous. It only stops if I shut off the water valve. Called plumber over to take a look. They said they’ve never seen this problem before. They called Navien and unfortunately my serial number was never registered so I’m told it isn’t under warranty. They are giving me the options to troubleshoot the unit for possibly $700 or more or to install a new one for about $5000. I figured at this point I’d try and troubleshoot it myself. I don’t know where to start though. We have had another plumbing issue with a leaky tub faucet. Seems like the water here is very hard. Any guidance would be appreciated. Thank you.