Occasionally, a hot water heater is a source of hydrogen sulfide odor. The magnesium corrosion control rod present in many hot water heaters can chemically reduce naturally occurring sulfates to hydrogen sulfide. Pleas visit this site it contains more infomation.
Have you removed the magnesium corrosion control rod from your water heater?
If removing the rod from the heater does not get rid of the odor I would suggest getting your water tested to find out if you have a H2S problem in your well.
Oh and remove that piece of galvanised pipe connecting your well tank, change it to a schedule 80 pipe nipple. It is not the source of your odor but it is a galvanic cell. This is when dissimilar metals are in contact with each other and with conductive water, generates electricity. The flow of electrons created by such a cell accelerates the corrosion of iron in contact with copper or brass, for example, by stimulating the flow of electrons away from the iron.
Respectfully David F. Walling