You might be right about that, Sylvan. One reason I chose to talk about how to purge a non-diaphragm expansion tank for a hot water heating system is that I find it hard to believe that someone will fool with a system that has 125+psig. It is not usual for a water heater to have a guage on it to know if the pressure is in fact rising. Certainly if the water pressure coming into a water heater is over 125, then there will be some other problems in the house. Someone who is asking about how to do this task without knowing anything about it is looking for danger. I just feel safer talking about a lower-pressure vessel.
The procedures are pretty much the same, but it should be done by someone with the experience to know that a leak at 125+psig can blind and cut skin. It is cetainly not a job for someone with no knowledge or even a helper without years of experience.
If it is a weeping valve from temperature, then handling hot water is not safe either; though the post didn’t mention that, just the rising pressure problem.