I am a DIY home owner in Michigan under the 2015 IPC. I sent my inspector a "How does this look?" picture via email. He responded that the hot water storage tank needs a vacuum relief valve. The code he is referring is "P2804.7 Vacuum-relief valve" and is referenced below. I attached a picture...
I have a typical solar hot water system with roof mounted panels and an external heat exchanger module plumbed to an 80 gallon glass lined storage tank that preheats water to a hybrid heat pump hot water tank
I will need to replace the storage/preheat tank that has begun to leak after 7 yrs...