Originally Posted by WayneG
It takes a lot to flush out the hot water tank. Let it fill, drain it through the bottom drain valve, refill and repeat 3 or more times. That may fix most of your problem.
If it has the slightest hint of sulfur, it may also be something other than antifreeze, maybe mold, algae or gunk, you will need to sterilize the tanks and lines.
Rotten egg odor is caused by hydrogen sulfide, which is common in well water systems. Sometimes the water won't smell at the source, but the anode in the water heater will react with sulfate in the water supply, reducing it to hydrogen sulfide gas, which smells strongly of rotten eggs or sewage. The best treatment for H2S is to keep a little bit of chlorine in your water at all times. Chlorine oxidizes H2S to elemental sulfur, which has no odor. It doesn't take much. And keeping your tanks chlorinated will prevent bacteria growth and keep your tanks clean, too.
For the OP (and everyone, really), I'd suggest using a drinking water filter like the Zerowater pitcher or the Berkey. There's a lot of things that could be in your water aside from off-tastes or odors. Thoroughly treated drinking water will help with all of it, even the things you didn't know about.