A compression valve is one of the easiest and quickest shut off valves to install if you have copper piping in your house. If the existing stop valves have sat unused for years chances are that they may not work perfectly, or at all, when you go to use them. That is why it is always a good idea to replace the valves when you replace a toilet
or faucet. Replacing a compression valve will help insure that it will work when you need it.