Do not connect plastic pipe or tubing directly to the UV system because the UV light will break down plastic in a short period of time. The best way to make the connection is with Dielectic Unions that allow for a connection from stainless steel to copper that will not corrode.
The union has a rubber bushing that keeps the dissimilar metals from contacting each other which would cause corrosion and leaks over time.
Dielectric Unions are available at plumbing supply stores but may be hard to find. We have them available at a very fair price, and if you order them from us you save time and do the job right.
If you have questions about how to properly install a UV system please call our staff of WQA Certified Water Specialists for assistance.