Plastic PEX fittings are OK
If you’re concerned about using plastic fittings instead of metal for PEX, worry no more. Professional plumbers are buying three times more plastic than brass. Brass fittings cost about five times as much, which likely has something to do with it. And pros don’t want a callback to fix their own work on their dime. So obviously, pros trust the plastic fittings. Manufacturers trust them as well; the warranties for plastic fittings are similar if not identical to those for their metal counterparts.
Metal fittings are required, however, where the fitting is exposed to UV light. Also, no plastic pipe or fittings can be used within 18 in. of water heating devices. Check your local building code in case there are other requirements where you live. Plus: Learn everything you need to know about PEX supply pipe here.