The 12 volt water pump is usually close to the fresh water tank , and you should be able to track it down by it's sound , with a tap open . You may have to remove panels for access.
Water heater by pass valve(s) are normally on the back of the tank and again removing a panel for access is a possibility.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.