Plumbing Fails. Pex plumbing installation. A few tricks and tips to make your installation a whole lot easier. See how to connect the fittings to the sink water lines using PEX water lines and PEX fittings. This is the BEST plumbing solution for beginner DIY plumbers! It’s so simple to install new water lines to your sink or “double sinks”. In this bathroom training video you will learn how to use PEX water lines and fittings to quickly and easily plumb your new bathroom sink! Bathroom Plumbing is SIMPLE to do if you have the right instructions to follow. Watch this diy bathroom plumbing video and learn a few Pro secrets for getting your sink water lines installed right the first time.