Grout will not be used, and can has been it is better a person to change it out with caulk. Dirty water could be a problem with heaters as well, and when you are experiencing this issue then if at all possible want look at the incredibly same thing, draining and flushing the entire tank. https://Healthwiz.co.uk/index.php?title=Why_Engage_A_Plumbing_Service_For_New_Installation