This purchase was to replace an Insinkerator hot water dispenser that was spurting air when drawing water. The customer service rep said it was a bad check valve and the whole tank unit needed replacing. I believe the check valve could be made to be serviced or replaced by putting it in-line with the tubing rather than attached to the tank. 
Other than that I love my hot water dispenser and have had one for probably 30 years in multiple houses. Can't get along without it.