I use our 2.5 acre tank as our water supply. We use it for baths, laundry, dishes etc. ( everything but our drinking water ) The problem is, since the lack of rain this year , the water is getting quite an odor . I have tried flushing the pressure tank with vinegar , which worked good for about three days, but I can think of nothing else to try. I know that most people do not have this problem since they are on city water , but any ideas would be helpful. Thank you.

How about using 35% food grade peroxide, would not know how much but just a thought! There are good internet sites in regards to the use of peroxide.

Do you have a way to blow air into it? The air should keep the smelly microbes at bay. If the temp of the tank water is above 80 degrees, no amount of air can help. You can lower the water temp by spraying the water into the air and back into the tank. The minor amount of evaporation that takes place while flying through the air cools it off and aerates it at the same time.