On many boats, mounting external sensors on the inside of a holding tank is too much of a hassle or is not an option because of where the tank is mounted. If the top of the tank is accessible, then it may be possible to install an internally mounted liquid-level sensor in the tank. Practical Sailor tested seven pre-packaged kits containing internally mounted tank-level sensors and remote monitor panels. Internally mounted tank-level sensors that used some form of float sensor were the SeaLand TankWatch1, Dometic DTM4, Groco TLM Series, and Wema SHS-8. Two test products used air pressure for reading: Fireboy-Xintex PTS and Hart Systems Tank Tender. And one product‹the…