rotten egg smell cold & hot water

It's not uncommon for well water to have bacteria which are perfectly harmless but which produce some sulfur-smelling gases. If they build up enough, the sulfur odor will be very noticeable. The solution for that is a chlorine (bleach) dose to the well. There are plenty of sites that give instructions for this. I have found that if we use our well water enough, the bacteria never build up to the point that we have any detectable odor in the house water. But, if you put the well water in your RV freshwater tank and don't use it immediately, the bacteria present in the water will reproduce and your RV water will smell like sulfur. The solution to that is, again, a bleach solution in the RV tank. To avoid that problem, I just don't use our well water to fill the RV tank if I can possibly avoid it.