MS5540 - water butt depth sensor

Assembly of the water depth sensor starts by soldering fine wires to the MS5540 sensor (datasheet) and adding a 47uf supply decoupling capacitor. A small amount of hot glue behind the sensor and around the capacitor gives stability to the flying leads. A polarised 8 way plug is used for testing & final assembly:

A Polyplumb 15mm Pipe Stiffner (black insert) is super-glued into a Polyplumb 22mm x 15mm Spigot Reducer (PB822). The sensor is welded in place at the end of the 15mm pipe stiffener using Araldite Rapid, and back-filled using a hot glue gun:

A finger cut from a nitrile glove is placed over the end of a short length of 15mm pipe. Final assembly uses a Polyplumb 15mm Straight Coupler (PB015) between the pipe and sensor assembly. The coupler is connected to the sensor assembly, held upright, filled with silicone oil, and the tube with nitrile finger attached. Some air will be trapped with the oil, but this doesn't prevent correct pressure detection. The complete assembly is ready to be attached to a cable running inside a length of 22mm pipe to the sensor box mounted above the water butt:

Earlier versions of the water sensors had the MS5540 glued into a rubber tap washer, encapsulated in hot glue, mounted at the end of a 15mm straight coupler connected via a spigot reducer to a 22mm straight coupler, and attached to a length of 22mm pipe. The MS5540 always failed after a few months due to water ingress under the MS5540 silicone gel: