PEX Installation Manual

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IM-PF 724596 0416
9.1 ManaBloc
The general sizing information shown may be
appropriate for many ManaBloc installations. These
recommendations are based on ow rates of typical
xtures that require 8 psi residual pressure.
The length of distribution tubing run between the Viega
ManaBloc and each xture shall be 60 feet or less
to maximize optimal performance of the ManaBloc
system. Exceeding this recommended distance affects
the system’s ability to efciently deliver hot water,
lengthening the time it takes for hot water to reach the
xture as well as increasing water waste.
9.1.1 Supply and distribution line sizing
The best water and energy savings of a ManaBloc
system are realized when distribution lines are sized
according to the xture demand and the length of
the individual line. Viega recommends the following
tube sizing:
Typical supply line size:
• ¾" up to 2½ baths
• 1" up to 4½ baths
Typical distribution line size:
• ⅜" up to 2½ GPM xture ow requirement
(lavs, toilets, bidets, bar sinks, kitchen sinks,
dishwashers)
• ½" up to 4 GPM xture ow requirement (hose
bibbs, tubs, showers, washing machines, whirlpool
baths, soaking tubs, etc.)
Consult the xture manufacturer’s literature to
determine the actual ll rate and residual pressure
requirements for distribution line size. In addition,
conrm with local Authority Having Jurisdiction (AHJ)
for acceptable PEX tubing size.
Hose Bibb Note: If a hose bibb is primarily for
irrigation purposes, it should be supplied from the
main service line prior to the ManaBloc.
A Viega PEX Press and PEX Crimp ManaBloc come
with ½" ports that are designed to t both ⅜" and ½"
PEX port adapters.
Design factors for installing a home run system
Water heater placement
The Viega ManaBloc should be as close as possible
to the water heater to minimize extra water from being
stored in the larger hot water supply lines between the
ManaBloc and water heater.
The longer the hot water supply line is, the greater
the volume of water needed to purge through that
line and faucet before hot water is available. This
creates water waste and longer hot water delivery
times.
9 Viega PEX System Design and Sizing
9.1.2 Plumbing code compliance
(home run / parallel systems)
The Viega ManaBloc system is listed to ASTM F876/
F877 standards for cross-linked polyethylene (PEX)
distribution systems. The below model plumbing
codes recognize and allow the use of PEX distribution
systems:
• International Plumbing Code (IPC)
• Uniform Plumbing Code (UPC)
• National Plumbing Code (NPC)
Sizing of Parallel Water Distribution Systems
(ManaBloc) is addressed in these model plumbing
codes under their respective water supply and
distribution sections. The Viega ManaBloc is also
IAPMO (UPC) and ICC-ES PMG listed for use with ⅜"
and ½" PEX tubing sizes for water distribution.
Proper water distribution line sizing to each fixture
This is crucial for overall system performance. If you
oversize a distribution line to a fixture (½" PEX line
supplying a sink instead of a ⅜" PEX line) you are
essentially doubling the volume of water being stored
in that line. It can take roughly twice as long to purge
an oversized line compared to a properly sized line.
The fixture is what dictates water flow (federally
mandated, governed by code). The tubing applies a
friction loss dictated by its size and length. Therefore,
as long as you do not undersize a distribution line
or run it excessive distances (60 feet or greater), the
system will perform properly, maintaining sufficient
pressure and flow.
The length of a distribution line run to
each fixture
This is just as important as properly sizing each
distribution line. Length of a distribution line run can
drastically affect the performance of a Viega ManaBloc
system. The longer the line is, the more water being
stored within it. Therefore, it will take longer to purge
it out before hot water can reach the fixture. The
ManaBloc should be located somewhat central to your
fixture groups, keeping within 60 feet or less of each
fixture for maximum performance.
If this cannot be accomplished with one ManaBloc,
multiple ManaBlocs may be required. Place one at
each end of the home to split the distribution line
distance between them. (See “12.5 Multiple ManaBloc
installations” on Page 30).