I have not seen the instructions. I do it on home units. Need to have service valves to make it easy. Service valves allow complete isolation of the heater and hook ups for hoses to circulate cleaning agent. Are there valves on your unit? Vinegar is the cleaner. Needs to be circulated through heater Using small pump. Hopefully some one can point you to the procedure on these rv units. I am not a fan of tankless heaters in general, endless hot water, but more maintenance.