I am building a log home and put in my well 3 years ago. It is 435' deep and it has a 3/4hp pump. Well produces 8-10gpm. When the well was put in we were using a camper on the property so we had the pressure tank buried at the well head. The well is about 200' from the house and the house is downhill from the well. There is a standpipe for a hose about halfway between the two. The only water hook up in the house is the upstairs bath which I finished first so that we would have a toilet, shower etc. We put that in about June. Everything was fine until about a week ago after I put in a spin down filter (to clear up fine sediment) and a uv light. Since then the the water pressure drops to about half after it has been running for about 5 minutes. If you turn off the water for about 10 minutes and then turn it on it has full pressure for another 5 minutes. I have a hose hooked to the standpipe and if I run that the pressure is fine but I have not run that yet for 5 minutes to see if it also drops off. I have to confess that I am not sure what type of pressure tank I have. I guess I am going to have to dig it up and see what is going on with it and then probably move it into the crawl space. It looks like from reading this forum that others have had similar problems and it has been suggested that a cycle stop valve would solve the problem. I haven't seen anyone post who has tried it and what the results have been-but then I might not have been looking in the right place. Does anyone have any suggestions or advice? Thanks. Sorry for the extra long post