Hi Pete and Tracey While researching prices on Suburban anodes I became confused by conflicting ads for magnesium and aluminium. I then came on the following in a thread on http://www2b.abc.net.au/science/techtalk/n...opic443564.shtm Quote: ">>>We recently had a problem with 'rotten egg' smelling water after some eight years of trouble free but very active motorhoming. Our water lines are all catering quality hoses and fittings. The cause has been traced to the HWS anode and by telling this story we may be able to help others avoid a similar baffling experience. Sacrificial anodes are built into Suburban hot water systems to protect the storage reservoir from corrosion. That is, the anode corrodes, first leaving the system intact provided the anode is replaced when necessary - which is normally at not more that two year intervals, and we have done this regularly. With the valued assistance of Coast-to-Coast RV Services we have been advised genuine Suburban anodes be made from magnesium. Unfortunately they look very similar to different anodes, which are made from aluminium and zinc to prevent corrosion in marine motors, which are constantly flushed with seawater. If a marine type anode is inadvertently fitted to a Suburban HWS, an opaque type jelly may eventually appear on the anode and a foul odour will affect the water, particularly if the system is not used frequently. Merely flushing with fresh water will not get rid of the odour. It is necessary to flush the system and replace the anode with a genuine Suburban magnesium part. Unfortunately we purchased our replacement marine type anode from a caravan repair business and assumed it was the right type. Hoping this tale may save other members from having contaminated water.<<<<<<<" I think I might also buy a couple of the EBay ones (fingers crossed)