Sulphur smell in hot water only...cold water is ok
Water heaters 101:Anodes are included in the water heater of glass-lined steel tanks to protect the inside of the tank against corrosion from acids in the water, stray electrical currents, etc. Glass lined tanks, when the water heater is being built, are heated up red hot. Then glass powder is sprayed inside the tank and it adheres upon contact. However, it doesn't cover every single crack and crevice inside the tank - it should, but in actual practice, it doesn't. The purpose of the anode is to protect those spots inside the tank that have not been glass-covered from rusting away prematurely. The anode is eaten away, rather than the tank being eaten away. Kind of a backup to the glass lining.The anode is a magnesium rod, about 3/4" in diameter that is attached to the inside of the hot water "out" nipple, via a plastic coupling. It is electrically isolated from the fittings and from the tank. It extends all the way across the inside of the tank, stopping just short of the other side. There is an iron rod in the center of the magnesium that supports it, the iron being stronger than the magnesium. As the magnesium is eaten away and the iron rod exposed, there's a chemical reaction between the water, the iron and the magnesium that causes the "rotten egg" smell. Replacing the anode and flushing out the tank will usually make the foul smell go away.Now for the bad news. Not all water heaters have glass lined tanks...the inexpensive ones have anodized aluminum tanks instead of a replaceable anode. When the anodizing has been eaten through, the only cure for the "rotten egg" smell in the hot water is a new water heater.If both the cold and hot water taste and smell funky, that can be cured by recommissioning the system, which should be done annually as part of spring recommissioning. I just posted directions for doing that last week, so you should be able to find 'em fairly easily.