Viega Manablocs have three “supply port” connections: one hot and one cold at the top, and one cold at the bottom. Since the Manabloc is partitioned internally into hot and cold sections, hot water from the water heater must enter through the hot port. Incoming cold water can enter through either cold port. Only Manabloc supply adapters or caps should be used at these connections due to their proprietary thread. The intended function of the second cold port is to feed cold water from the Manabloc to the water heater. Many applications include a tee on the cold feed line prior to the Manabloc as an alternate method of feeding the water heater. In these cases, install a Manbloc supply end cap (part 53601) to seal the unused cold supply port. Refer to the diagrams below for example cases. Neither method offers any major advantage over the other. The tee/cap method may save some space for installations in tight spots, but it creates two additional fitting connections, which are always more likely to leak than a piece of tubing.