Viega46656 PureFlow Zero Lead Additional Manabloc Supply Adapter with 1-Inch by 1-Inch Connection x Manabloc Supply

Ideal for larger Viega Manabloc manifolds that demand a larger water supply line. Installs easy in the Manabloc supply port. Threaded 1 inch male adapter allows you to adapt to almost any type of water supply pipe.

Expensive but they are the best you can get.