Two small, inexpensive components that prevent two very expensive failures — here's what they do and why contractors install them as standard practice.
When a submersible pump motor starts, the reaction torque tries to spin the entire pump and drop pipe assembly in the opposite direction of the motor shaft — for a split second on every single start. Without something to absorb that twist, the pipe can rub against the casing wall repeatedly over thousands of cycles, wearing through wire insulation and eventually causing a short. A torque arrestor is a rubber or plastic fin clamped near the pump that presses against the casing wall and absorbs that rotational force instead of letting the whole assembly twist.
The safety rope (sometimes called a safety cable) is a separate line, usually stainless steel or polypropylene, attached to the pump and secured at the well cap — completely independent of the drop pipe and wiring. If a pipe coupling ever fails, the safety rope is what keeps you from losing an entire pump assembly down the well, which otherwise means fishing for it or drilling a new well entirely.
Contractor standard: Both components together typically cost under $30 and take a few extra minutes to install during initial pump setup. Most professional installers include them by default, but older wells or DIY installations sometimes skip one or both.
You generally can't verify this without pulling the pump, since both components are below the well cap. If you don't have installation records or don't know when the pump was last serviced, ask your well contractor to check next time the pump comes out for any other reason — adding both at that point is inexpensive.
Repeated wire insulation failures at roughly the same depth, or a pump that developed an electrical short years before the motor's expected lifespan, can sometimes trace back to a missing or worn-out torque arrestor letting the assembly rub against the casing on every cycle.