I am moviing a 2.5 ton Rheem heat pump to another house. How do I shut it down to save the freon?

You need to have a set of refrigeration manifold gauges and/or a recovery unit. If you have never pumped one down before I recommend you call a service technician. Heat pumps can be tricky with the reversing valves.

Just a warning, there is a $25,000 reward for turning is a person that releases freon into the atmosphere. He or she does not have to prove that you did it but you have to go through hell trying to prove that you didn't. And there are lots of people that will turn you in if they think they will gain anything at all.

Don't try it. If you do not know what your doing it will only cost you a lot more for a tech to come out and fix what you did wrong and replace the freon you lost. ( If you do try it make sure to buy a filter drier to put back in when you hook it back up.)

You will need a filter drier that's approved for a heat pump installation. They have internal check valves that allows flow and filtration in either direction. You will also need a vacuum pump to remove the air and moisture out of the system before charging it.

Plus you should use nitrogen and purge the new system while brazing in the new line set with silver or other alloy brazing rods. In short, 1500 dollars worth of tools later, maybe you would be better to find a good, reputable, pro to move it for you.