PSC 31/32 fresh water cooling system

[Drifting]

I have to replace the 3JH2E fresh water pump on a 32 pilothouse (coolant dripping out of weep hole).

I thought this might be a good time to insert a valve after the pump outlet to control circulation of hot water through the Atwood hot water tank - it is near-boiling hot when the engine is running. BUT after following the somewhat convoluted tubing, it looks as though the line from pump to Atwood tank inlet runs via the sub/header tank (both tanks are in the port cockpit locker). So not a good idea to shut this flow off...

Are my observations correct - is this the standard layout of the system?