Im posting for my sister and Im not at her place but wondering where I should start. The water is not getting hot anymore. Google is my friend and its telling me either the element or thermostat? What are the most common causes? It states between 15-30 ohms for a good element, how do I test the tstat and what are the prices for each? I dont know what kind yet but am wondering if it could be cheaper to get a new one or not? Thanks in advance.