I had a leak somewhere in my central air unit. The contractor told me there was a leak but couldn't find it. He then put 4lbs of R-22 in the system, gave me a bill which I paid, and he left. Two weeks later all the R-22 leaked out. Someone told me it was against the law to do this, something about the EPA and the Clean Air Act?

 

Well, yes.
Technicians are required to find the leak before they add refrigerant.
The problem is that there is some tolerance for leaks that are very slow as it is difficult to find leaks that take years to be a problem.

Now that you know it is a fairly large leak you would do well to call the same tech back and insist he locate the leak.
If you ensure you are home when he is there you can ask him to show you the leak before he repairs it.

 

The issue I'm having is that he did come out a second time, tried to fix the problem with leak sealant, and came out a third time, to put more leak sealant in, because the first can didnt work right. Each time he had to put refrigerant in my system. Now Im being charged for the second and third time he was out.

 

Leak sealant ugh, he's doing more damge then good.
You have two options, call them back and make them fix the leak.
Or find another HVAC company to do the job right. At this point, you really should have the sealant removed from the system. They are known to cause complete system failures down the road and should only be used as a last measure. A leak that large should be easy to spot. If they don't fix it, file a complaint with the BBB.

 

Hmm,
I only do commercial work and am not totally familiar with residential HVAC techniques but 'leak sealer" in my circles is viewed as wishfull thinking.
The proper way to handle this is to positively identify the leak then repair with a weld or other permanent solution.

Leak sealer works on the premis that a syynthetic seal is leaking and a chemical that will cause a neoprene seal to swell will fix a leak.
IMO this belief is a joke.

The leak should be positively found and verified with either bubbles from a liquid media or a positive and repeatable response from an electronic leak detector.

 

Actually in America refrigerant can be added to residential and small commercial units without having to find the leak. And leak sealant which personally I'm not a fan of, is used and many companies say it works. So legally I dont think you can do anything. If the refrigerant leaks out in two weeks it shouldn't be too hard to find the source of that BIG LEAK. Hopefully you can find someone who can find it. It might be in the lines underground or behind a wall but it must be found before anything else is done.