I recently bought a home that has a tankless water heater. Everything was fine until I decided to raise the water temp from 115 degrees to 135 degrees. Shortly after my faucets all have fairly large chunks of solids coming out. In fact I think it may have damaged my Moen faucet in my tub. I tried flushing out the system by running loads of water through the tub faucet but the flakes still kept coming. I'm almost positive that the rise in temp loosened buildup in the water heater. It does not have the service valves for cleaning so I assume it hasn't been cleaned since installation in 2014. My question is, can I install the service valves and flush the heater or is it too far along for that? Do I need to replace or could it be something else. Most of the plumbing is new PEX but not sure what was in the system before. No softener of filters are installed. Thanks in advance.