On the Suburban site, it says this:
Each year drain the water from the system and flush the heat exchanger with an approved descaling solution and use of our kit 521163. Contact your local RV service center for assistance.
Doing a search for Suburban approved descaling solution brought up several items, and this is one of them:
https://www.homedepot.com/p/Hercules...E&gclsrc=aw.ds
Not sure what that part number is for.