Installation Guide

ManualsBrandsRheem ManualsPlumbingPerformance Platinum 9.9 GPM Natural Gas High Efficiency Indoor Recirculating Tankless Water Heater

Details regarding

properly sized gas

lines for use with

tankless water

heaters and other

gas appliances

With any gas appliance, it is essential that the gas supply system be properly sized to support the

BTU load of the system. Tankless water heaters can be a great solution to provide hot water;

however, most tankless water heaters have a BTU capacity ranging from 140,000 to 200,000 or more,

which makes a tankless water heater one of the largest single appliances on a typical gas system.

It is necessary to ensure that the system can handle the capacity of the tankless water heater

along with all other gas appliances on the system. This guide will address the fundamentals

and facts of gas pipe sizing for low-pressure (under 2 psi) natural gas systems using rigid iron pipe.

For other gas systems, including Propane, Hybrid Pressure, Copper Pipe, and CSST, please consult

your local code or the National Fuel Gas Code, NFPA54, ANSI Z223.1 - 2012 Edition.

GAS PIPING

INFORMATIN

FOR TANKLESS WATER HEATERS

Summary of content (6 pages)

PAGE 1
GAS PIPING INFORMATION FOR TANKLESS WATER HEATERS Details regarding properly sized gas lines for use with tankless water heaters and other gas appliances With any gas appliance, it is essential that the gas supply system be properly sized to support the BTU load of the system.
PAGE 2
Gas Pipe System Facts Will a tankless water heater work on a ½-inch gas line? Yes and No. A typical residential gas system is a low-pressure system, meaning that the home is supplied with a gas pressure around 7 in. w.c. (inches of water column). The piping must be sized sufficiently enough so that the pressure drop is a half an inch of water column or less, when all the gas appliances are on.
PAGE 3
Gas Pipe System Sizing Figure 1 - Typical Gas System with a Tankless Water Heater Gas Dryer (25,000 BTU) Furnace (75,000 BTU) Tankless Water Heater (199,900 BTU) G 15 ft E 20 ft C 15 ft J 20 ft D 30 ft Branch 1 Total 274,900 BTU A B 30 ft Branch 2 Total 120,000 BTU H 30 ft K 10 ft 20 ft Trunk Line Total 394,900 BTU Gas Logs Fireplace (40,000 BTU) Gas Range (55,000 BTU) Gas Meter (395 Cubic Feet) Determining the Required Meter and Regulator size.
PAGE 4
Gas Pipe System Sizing Table 1 - Gas System Branch Sizing Example based on Figure 1 Line Segment Branch 1 Branch 2 Main Trunk Appliance BTU Required Line Length E Tankless Water Heater 199,900 G Gas Furnace D Minimum Pipe Size Required 0.3 w.c. drop 3.0 w.c. drop 20 ft 1” ½” 75,000 15 ft ½” ½” Branch Main Line 274.
PAGE 5
Gas Pipe Capacity Charts Table 2 - 0.3 Inch Water Column Pressure Drop for Black Iron - Schedule 40 Metallic Pipe Pipe Size (in.) Nominal Dia.
PAGE 6
Rheem helps you give your customers the value, performance and features they want. From our tried and true tank-type water heaters to our space-saving tankless solutions that provide continuous hot water, Rheem has something to satisfy the budgets and lifestyles of every customer. In addition to our large selection of water heating solutions, Rheem also has a full line of heating and cooling products, parts and accessories for warm winter nights, cool summer days and hot water all year long.