Help! How to uncouple corroding unions?

[tec]

Have a Bradford White LP gas water heater. 12 yrs. old. The pipe connections are corroding. I want to replace them before a real problem develops; but I can't determine how to disconnect the water lines without cutting them. There does not appear to be a way to use a wrench to uncouple them. What am I missing?

 

[djmayhill]

That's because there are not you would have to cut the pipe to unthread those

 

[ExtraMilePlumbing]

12 year old water heater, hate to say it but you need a new one .