A discussion on hot water system requirements in the 2009 International Plumbing Code -- Part II
By Ron George, CIPE, CPD
President, Ron George Design & Consulting Services
This is the second part of Ron George’s discussion on hot water requirements in the 2009 International Plumbing Code.
Some of the Chapter five water heater requirements are discussed below:
2009 International Plumbing Code, Chapter 5 — Water Heaters
Section 501 — General
501.1 Scope. The provisions of this chapter shall govern the materials, design and installation of water heaters and the related safety devices and appurtenances.
Water Heater Requirements: Section 501.2 addresses combination potable water heating and space heating systems at temperatures higher than 140 degrees Fahrenheit and requires these system to have a temperature actuated master mixing valve conforming to ASSE 1017 to limit the hot water temperature to 140 degrees Fahrenheit. I have never found a system that was combined that did not have problems at some point in its existence. I would not recommend designing or installing a combined system, because you often have someone working on one half of the system that does not understand the other half of the system’s design parameters. If you are going to design one of these systems, I would recommend always installing a master mixing valve and making sure all the components are suitable for domestic water systems. Many components of the hydronic system such as coils, valves, strainers and circulators get replaced over time with components that are not designed for use in the domestic water system. These systems are often the cause of scalding incidents where the system temperature is turned up in cold winter months, because these design temperature is exceeded or the system looses capacity of one boiler in a multiple boiler situation. The common solution for the building maintenance personnel is to turn up the temperature which often leads to scalding incidents.
I feel this code section should be amended to require temperature actuated mixing valves conforming to ASSE 1070 be used on all combined systems to reduce the domestic hot water temperature at each apartment, condo or group of fixtures for bathing, showering or hand-washing because of their ability to contribute to scalding incidents. The current code text is as follows:
501.2 Water heater as space heater. Where a combination potable water heating and space heating system requires water for space heating at temperatures higher than 140°F (60°C), a master thermostatic mixing valve complying with ASSE 1017 shall be provided to limit the water supplied to the potable hot water distribution system to a temperature of 140°F (60°C) or less. The potability of the water shall be maintained throughout the system.
Water Heater drain valves are required to conform to ASSE 1005.
501.3 Drain valves. Drain valves for emptying shall be installed at the bottom of each tank-type water heater and hot water storage tank. Drain valves shall conform to ASSE 1005.
The following text addresses other requirements for water heaters:
501.4 Location. Water heaters and storage tanks shall be located and connected so as to provide access for observation, maintenance, servicing and replacement.
501.5 Water heater labeling. All water heaters shall be third-party certified.
501.6 Water temperature control in piping from tankless heaters. The temperature of water from tankless water heaters shall be a maximum of 140°F (60°C) when intended for domestic uses. This provision shall not supersede the requirement for protective shower valves in accordance with Section 424.3.
501.7 Pressure marking of storage tanks. Storage tanks and water heaters installed for domestic hot water shall have the maximum allowable working pressure clearly and indelibly stamped in the metal or marked on a plate welded thereto or otherwise permanently attached. Such markings shall be in an accessible position outside of the tank so as to make inspection or reinspection readily possible.
Water Heater Temperature Controls:
The following text requires the water heater to have temperature controls. The temperature controls on a water heater do not accurately control the hot water temperature leaving a water heater so, the text in section 501.8 should probably be changed to say “energy controls.” The controls on a water heater are typically not capable of accurately controlling water heater outlet temperatures. Last year I submitted a code change to the 2012 International Plumbing code to reintroduce code language that mysteriously disappeared from the code in the last few years, but I could not find where there was a code change that took the language out of the code. The code change I submitted was accepted and will appear in the 2012 edition of the plumbing code. The code change does not allow the thermostat on the water heater to be the final system temperature control. This has been discussed in detail in other columns, but basically the water heater burner thermostat or energy controls on an un-circulated water heater can allow temperatures to fluctuate as much as 30 to 40 degrees from the “burner on” oer “cut-in” temperature to the “burner off” or “cut-out” temperature. A temperature swing of thirty to forty degrees is not accurate enough to prevent exposure to hazardous, unsafe scalding hot water temperatures.
501.8 Temperature controls. All hot water supply systems shall be equipped with automatic temperature controls capable of adjustments from the lowest to the highest acceptable temperature settings for the intended temperature operating range.
The following 2009 IPC code language addresses Water Heater installations:
2009 International Plumbing Code
Section 502 — Installation
502.1 General. Water heaters shall be installed in accordance with the manufacturer’s installation instructions. Oil-fired water heaters shall conform to the requirements of this code and the International Mechanical Code. Electric water heaters shall conform to the requirements of this code and provisions of NFPA 70. Gas-fired water heaters shall conform to the requirements of the International Fuel Gas Code.
502.1.1 Elevation and protection. Elevation of water heater ignition sources and mechanical damage protection requirements for water heaters shall be in accordance with the International Mechanical Code and the International Fuel Gas Code.
502.2 Rooms used as a plenum. Water heaters using solid, liquid or gas fuel shall not be installed in a room containing air-handling machinery when such room is used as a plenum.
502.3 Water heaters installed in attics. Attics containing a water heater shall be provided with an opening and unobstructed passageway large enough to allow removal of the water heater. The passageway shall not be less than 30 inches (762 mm) high and 22 inches (559 mm) wide and not more than 20 feet (6096 mm) in length when measured along the centerline of the passageway from the opening to the water heater. The passageway shall have continuous solid flooring not less than 24 inches (610 mm) wide. A level service space at least 30 inches (762 mm) deep and 30 inches (762 mm) wide shall be present at the front or service side of the water heater. The clear access opening dimensions shall be a minimum of 20 inches by 30 inches (508 mm by 762 mm) where such dimensions are large enough to allow removal of the water heater.
502.4 Seismic supports. Where earthquake loads are applicable in accordance with the International Building Code, water heater supports shall be designed and installed for the seismic forces in accordance with the International Building Code.
502.5 Clearances for maintenance and replacement. Appliances shall be provided with access for inspection, service, repair and replacement without disabling the function of a fire-resistance-rated assembly or removing permanent construction, other appliances or any other piping or ducts not connected to the appliance being inspected, serviced, repaired or replaced. A level working space at least 30 inches deep and 30 inches wide (762 mm by 762 mm) shall be provided in front of the control side to service an appliance.
The following 2009 IPC code language addresses connections to water heaters:
2009 International Plumbing Code
Section 503 — Connections
503.1 Cold water line valve. The cold water branch line from the main water supply line to each hot water storage tank or water heater shall be provided with a valve, located near the equipment and serving only the hot water storage tank or water heater. The valve shall not interfere or cause a disruption of the cold water supply to the remainder of the cold water system. The valve shall be provided with access on the same floor level as the water heater served.
503.2 Water circulation. The method of connecting a circulating water heater to the tank shall provide proper circulation of water through the water heater. The pipe or tubes required for the installation of appliances that will draw from the water heater or storage tank shall comply with the provisions of this code for material and installation.
The following 2009 IPC code language addresses the domestic hot water supply piping system:
2009 International Plumbing Code,
Section 607 — Hot Water Supply System
607.1 Where required. In residential occupancies, hot water shall be supplied to all plumbing fixtures and equipment utilized for bathing, washing, culinary purposes, cleansing, laundry or building maintenance. In nonresidential occupancies, hot water shall be supplied for culinary purposes, cleansing, laundry or building maintenance purposes. In nonresidential occupancies, hot water or tempered water shall be supplied for bathing and washing purposes.
Tempered water shall be supplied through a water temperature limiting device that conforms to ASSE 1070 and shall limit the tempered water to a maximum of 110ºF (43ºC). This provision shall not supersede the requirement for protective shower valves in accordance with Section 424.3.
607.2 Hot water supply temperature maintenance. Where the developed length of hot water piping from the source of hot water supply to the farthest fixture exceeds 100 feet, the hot water supply system shall be provided with a method of maintaining the temperature in accordance with the International Energy Conservation Code.
607.2.1 Piping insulation. Circulating hot water system piping shall be insulated in accordance with the International Energy Conservation Code.
Section 607.2.2 is copied into the plumbing code from the energy code. This requires a circulating hot water system to be turned off during periods of non-use. This type of control should not be used in buildings with non-compensating type shower or bathtub controls with maximum temperature limit stops. If this type of control were installed in a system where a non-compensating type or two-handled shower control was installed without a maximum temperature limit stop, a bather could turn the shower temperature to full hot and be in the shower for a significant period of time before the full hot water arrived. This condition can and has caused serious scald injuries. Caution should be used when turning off a circulating pump. Make sure all bathing and showering fixtures have properly set maximum temperature limit stops before employing these type of energy controls. The [E] designation prior to the code text indicates it is an energy code requirement printed here for purposes of clarity.
[E] 607.2.2 Hot water system controls. Automatic circulating hot water system pumps or heat trace shall be arranged to be conveniently turned off, automatically or manually, when the hot water system is not in operation.
This is another code section that I submitted to the International Plumbing Code many years ago because most but not all mixing valve manufacturer’s require the tempered water return line to split and flow to both sides of the mixing valve for proper operation. This requirement is printed in some o the manufacturer’s installation literature but not every one. By not piping a mixing valve properly with a circulating pump it creates a condition where someone can get scalded.
607.2.3 Recirculating pump. Where a thermostatic mixing valve is used in a system with a hot water recirculating pump, the hot water or tempered water return line shall be routed to the cold water inlet pipe of the water heater and the cold water inlet pipe or the hot water return connection of the thermostatic mixing valve.
Section 607.3 requires a means for relieving thermal expansion other than the temperature and pressure (T & P) relief valve on the water heater. If the T & P valve is relied upon the system pressure must get up to 150 pounds per square inch which far exceeds tha maximum allowable pressure of 80 PSI in section 604.8.
607.3 Thermal expansion control. A means of controlling increased pressure caused by thermal expansion shall be provided where required in accordance with Sections 607.3.1 and 607.3.2.
607.3.1 Pressure-reducing valve. For water service system sizes up to and including 2 inches (51 mm), a device for controlling pressure shall be installed where, because of thermal expansion, the pressure on the downstream side of a pressure-reducing valve exceeds the pressure-reducing valve setting.
607.3.2 Backflow prevention device or check valve. Where a backflow prevention device, check valve or other device is installed on a water supply system utilizing storage water heating equipment such that thermal expansion causes an increase in pressure, a device for controlling pressure shall be installed.
There was an old saying that has been passed all around the plumbing industry and one version of it was “All a plumber needs to know was hot on the left, cold on the right and waste flows downhill” Section 607.4 is where it requires hot water to flow from the left side of a fixture. However, since the time of that old saying, we have come out with whirlpool tubs and bathtubs that have the faucets mounted on a deck. The question is then, Does the left hand side apply to the person adjusting the controls standing outside the tub or does it apply to the person sitting inside the tub? Well the answer to that question is in the exception listed below section 607.4. It requires markings on the faucet to correspond to the hot and cold temperature flowing from the faucet.
607.4 Flow of hot water to fixtures. Fixture fittings, faucets and diverters shall be installed and adjusted so that the flow of hot water from the fittings corresponds to the left-hand side of the fixture fitting.
Exception: Shower and tub/shower mixing valves conforming to ASSE 1016 or ASME A112.18.1/CSA B125.1, where the flow of hot water corresponds to the markings on the device.
Ron George is president of Ron George Design & Consulting Services. He has served as Chairman of the International Residential Plumbing & Mechanical Code Committee. He is active in plumbing code and plumbing product standard development committees with ICC, IAPMO, ASSE, ASME, ISEA and ASTM. His company specializes in plumbing, piping, fire protection and HVAC system design and consulting services. He also provides plumbing and mechanical code consulting services and he provides investigations of mechanical system failures and litigation support. To contact Ron, email: rgdc@rongeorgedesign.com.