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8
Water Plumbing
Follow local guidelines for the length of the
plumbing line in order to ensure that there is
enough water pressure for all the fixtures on the
line. First, calculate the effective length of the
plumbing line by measuring the total length of pipe,
and then adding to this 5’ for each elbow or tee in
the line. Use the following chart to determine the
total number of fixture units on the line, and then
compare with the chart at the bottom of this page
to find the pipe diameter and water pressure
necessary.
Install with control valves on the inlet and outlet,
and use removable unions or connectors to
facilitate maintenance or service if necessary.
If the water heater is installed in a closed water
system; means shall be provided to control thermal
expansion. Contact the water supplier or a local
Plumbing Contractor on how to control this
situation.
Purge the water line of air, and clean the filter
before initial operation.
WARNING:
Do not reverse the hot outlet and
cold supply line connections to the Flash Water
Heater. Make sure the hot and cold lines are
connected as in the FOR YOUR SAFETY section
at the front of this manual.
Pressure Relief Valve
An approved pressure relief valve must be
installed in any installation with this unit. The
pressure relief valve must be installed on the hot
line out of the unit, with no check valves or control
valves between the unit and the relief valve. It is
recommended to install the pressure only relief
valve 6” inches away from water flow to prolong
the life of the Pressure relief valve.
The Pressure only relief valve must be rated for
150 PSI, and have a discharge capacity of
190,000 BTU. Connect the discharge opening of
the relief valve to a suitable drain to prevent water
damage should discharge occur.
If the pressure relief valve discharges periodically,
this may be due to thermal expansion in a closed
water supply system. Contact the water supplier or
local plumbing contractor on how to correct this
situation.
Do not plug the pressure relief valve. The line
should have no reduced fittings or other
restrictions and should allow for complete drainage
of valve and line. The pressure relief valve should
be manually operated once a year to check for
correct operation.
Should overheating occur or the gas supply fail to
shut off, turn off the manual gas control valve to
the appliance.
Length to the End of Hot Water Line and Recommended Fixture Units
Pipe
Size
Pressure Range 30 to 45 PSI Pressure Range 46 to 60 PSI Pressure Range 60+ PSI
Length
100' 200' 300' 400' 100' 200' 300' 400' 100' 200' 300' 400'
3/4" 3-12 1-6 1-5 0-4 5-17 3-11 2-8 1-6 6-20 4-13 3-10 2-8
1" 12-25 6-17 5-13 4-12 17-36 11-25 8-20 6-18 20-39 13-32 10-26 8-22
1-1/4" 25-48 17-32 13-25 12-21 36-78 25-52 20-39 18-33 39-78 32-74 26-54 22-43
Fixture Unit Per Fixture (from UPC)
Plumbing Fixture
Description
Fixture
Unit
Combination Bath / Shower 4
Whirlpool Bath 4
Shower 2
Lavatory 1
Clothes Washer 4
Dishwasher 1.5
Kitchen Sink 1.5