Originally Posted by
LLigetfa
Are you on municipal or well water? Do you have an iron filter or softener?
Sometimes air may be en-trained in the water as part of the treatment process. When aerated water is heated, it releases the air. That is why a hot spell can kill a lot of fish.
Many iron filters work by aeration. Water softeners that don't properly shut off the brine line can draw in enough air to later cause spitting at faucets.
When you drained the bladder tank, did you make sure it had the proper precharge or did you trap air above the water? Did you verify that the bladder is sound?