Shaft Anodes

The correct method is to measure the shaft diameter directly, ideally with a caliper. If that is not possible, measure the circumference and calculate the diameter, but direct measurement is best. Once you know diameter, confirm the anode width and profile so it fits within available clearance. Also check the clamp style and bolt layout. If you can share your diameter and a photo of the shaft area, it is usually enough to confirm the right option.

Material choice depends on your typical water type and what you use elsewhere on the same system. Many owners choose zinc or aluminium depending on salt or mixed conditions, and magnesium is commonly used in fresh water. The practical approach is to keep material consistent across the same protected system so wear behaviour is predictable. If you tell us your water type and the rest of your anode material choice, it is easier to guide selection.

A loose anode is usually caused by incorrect diameter selection, poor tightening, or contamination under the clamp that reduces friction. Confirm the anode is the correct diameter and that the shaft surface is clean before fitting. Tighten bolts evenly and re-check after a few trips. Also confirm the anode width does not foul nearby fittings, which can create movement. If anodes repeatedly loosen, inspect for shaft surface issues and consider whether the clamp style suits your setup.