Here’s the truth: Your black tank probably has old poop and paper that is left-behind from your camping trips that needs to be flushed out. Even if you’ve been using a high quality holding tank treatment (like brushing your teeth everyday) you still need to do a deep clean every once in a while (like a visit to the dentist for a professional cleaning). Left-behind waste can cause odors and misreading sensors that are easy to fix if you just flush out the waste. | Unique Camping Marine