Speedbump, Thanks for responding back with my questions.
How my previous set up was that even though the 1.5HP motor/pump has a check valve installed in it I believe, the well installers I have talked to still use a external check valve. I have roughly 280' of galvanized piping in 21' increments screwed together that is attached to a brass check valve that is attached to the motor/pump. They put the new 2.0 HP motor/pump together and then attached the brass check valve and then screwed the first 21' of galvanized piping and lowered the assembly down the well and then added the next section and so on. Inside of the house I have a Well-Tron bladder tank.
On the 1.5 HP motor/pump that had the hole in the line, I was there when they pulled it up and it was the same. The last section of galvanized pipe was screwed into a brass check valve that was attached to the motor/pump. You could see the hole that was on the galvanized pipe threads just outside the check valve. The check valve was unscrewed from the galvanized pipe and the whole wall on the galvanized pipe threads on the inside were deteriorated and weakened as the thickness was gone. This is the section of pipe that was replace and they reused the other sections but switched the 4 sections of galvanized pipe that were in the water with 4 sections of galvanized pipe that were out of the water.
They told me that it was caused by electrolysis from the dissimilar metals. What they did now is use tape sealant on the threads of the galvanized piping where it threads into the brass check valve that is screwed onto the outlet of the 2.0 HP stainless motor/pump.
After it was installed, they did run the well for about 30 minutes and did a rate check on the water coming out of the well at the casing. It function like it should and then it was lowered the rest of the way using the fitting that attaches to the pipe that takes it into the house. After that I ran the well for about 6 hours using the outside faucet. However, it has been 4 days and we are still getting the black Sulphur on the Rusco filter requiring us to cleaning it. The time between cleaning is getting better but before that we had gone 2 months with the filter in and had done nothing but crack the drain valve but never had to remove the filter.
I had to replace the tank on the water softener and it took 2 days after the new 2.0 HP well pump/motor was installed before it was returned. I showed the tech the black stuff on the filter. I had read your post and am pretty sure it is Sulphur as it has the properties you describe. The water softener tech said that the water softener will have no problem filtering the black Sulphur and then the backflow it uses to clean itself will remove the stuff from the water softener. I was a little hesitant about removing the filter as I didn't want to hurt or worse plug up the water softener but will probably go ahead now after reading this thread.
You are right that the higher pump /motor (2.0 HP versus 1.5 HP equating to 15 gpm versus 10 gpm) than previously installed is probably over kill but it really wasn't that much more given the total price and it will give me the option of using it for irrigation of the lawn for a limited area I want to do. I know the pump isn't strong enough to do a large area for irrigation but that is fine.
When talking with the well person, he did mention that if the black particles continues that they could come back in put air in the well to clean it out. I assume this is what you are talking about when you mention using your air compressor on the house lines. I am curious how this is done on the well itself? Is it safe to assume an air line is put down the well and air is introduced to make the water turbulent to break off all the Sulphur so when you run a outside faucet, it all pumps out? If so, this is something I may have to do.
As I have done some plumbing work on the inside of the house and in a section of copper plumbing I removed, the inside was all black like you mentioned. At least I know now what is causing this.