Viega MANABLOCs arrive fully assembled and factory tested. They include individual quarter-turn port shutoff valves, which allow the end user complete control over the entire plumbing system from one central location. Fewer behind-the-wall fittings make it easy to install and less likely to leak. Flexible ViegaPEX tubing in 3/8'' and 1/2'' ensures optimal efficiency required to supply fixtures. The choice to install 3/8'' PEX tubing for low-demand fixtures instead of 1/2'' will determine how much water an end user can save with a Viega MANABLOC system. In a length of 50 feet of PEX tubing, 3/8'' PEX stores only .32 gallons of water (as opposed to 1/2'' PEX tubing's .46 gallons). Storing less volume of water means less time is required to purge the line and deliver hot water twice as fast as with a 1/2'' PEX line. Viega MANABLOC is a complete plumbing system that is easy to install and provides fast hot water delivery by decreasing energy costs and reducing water waste.