Yes. There are several ways to do this depending on the system that you want to combine. For example if you want to go from Copper to CPVC there are fittings that will allow a copper solder or threaded connection on one side and a solvent weld on the other side to the CPVC. If you are trying to go from Copper to PEX, there are fittings that will allow this also. Now if you want to connect any one of these to another system, there are fittings that will allow you to interconnect the PEX, CPVC and Copper with one handy fitting. There are a few brands of these types of connections, with two of the most common being, SHARKBITE and GATERBITE. These fittings utilize a system of rubber seals and spring-loaded rings to make watertight, permanent connections from pipe type to pipe type. One huge advantage of these fittings is the ability to remove the fitting without any special tools. The disadvantage is that they cost nearly 5 to10 times the cost of a regular fitting. Check with your local building codes as well to ensure these are acceptable in your area.