I have an eccotemp thats been running for about 6 yrs but it has some issues. I have been looking for this one as a replacement.
https://www.amazon.com/Excel-Tankless-Demand-Heater-VENTFREE/dp/B0977N2DB3/
They have a 'low pressure startup' technology that the eccotemp doesn't have.
Cool, I've been doing some research and it seems like most of them require 20-30 PSI.
However, I just found one that "Starts with only 2 PSI of Water Pressure".
According to my research, I can get that much pressure by elevating the water tank 5 feet above the heater, does that sound right to you?
Excel Tankless On-Demand Gas Water Heater VENTFREE – Propane (LPG) - Low Water Pressure Startup https://www.amazon.com/dp/B0977N2DB3/ref=cm_sw_r_cp_api_glt_fabc_7PS5VJ3J72KRGYXTAFQV?_encoding=UTF8&psc=1