Source google image: https://www.picclickimg.com/00/s/ODAyWDYwMQ==/z/pCgAAOxyIv5TkIQ~/$/Sale-Price-Rinnai-3-4Tankless-Water-Heater-Isolation-Valve-LEAD-_1.jpg
4 isolation valve
Source google image: https://www.picclickimg.com/00/s/ODAyWDYwMQ==/z/pCgAAOxyIv5TkIQ~/$/Sale-Price-Rinnai-3-4Tankless-Water-Heater-Isolation-Valve-LEAD-_1.jpg