Water Piping
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 inspector
on how to control this situation.
Important: 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.
The Pressure relief valve must be rated for 150 PSI.
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 inspector 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.
Length to the End of Hot Water Line and Recommended Fixture Units
Pressure Range 30 to 45 PSI Pressure Range 46 to 60 PSI Pressure Range 60+ PSI
Pipe
Size
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
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