Preventing the Scald
By Peter Gobis III
Now that more than half of the U.S. has adopted the 2009 International Plumbing Code (IPC) at the state level, and about another dozen states administer the code at the local level, understanding how to comply with water mixing devices has become a hot topic.
According to the 2009 IPC, tempered water for non-residential occupancies shall be supplied for bathing and washing purposes. The code specifically mandates the delivery of tempered water with a device that limits water temperature to a maximum of 110ºF.
The portion of the code pertaining to public hand washing applications is particularly drawing discussion because it marks a major shift in temperature control requirements. All public sinks must now use an ASSE 1070 device to limit final temperature. How one interprets the code and installs 1070 devices can differ, however: Some inspectors interpret the code and prefer that a 3/8" point-of-use valve is used for each sink, whereas others deem that a ½" or ¾" unit for a bank of lavatories is adequate.
Either of these approaches can work, and they are both vast improvements over installing a mechanical mixer that does not have an internal thermostatic device to make modifications for incoming temperature changes. Stricter guidelines and code enforcement are intended to better safeguard end users in public hand washing applications, which will continue to drive significant increases in point-of-use products — however professionals choose to comply with the code.
ASSE 1016 for showers
Shower applications are also greatly affected by the code change. The IPC now requires ASSE 1016 devices that regulate water temperature and/or pressure.
There are currently three shower valve classifications for 1016. The first is a Type T thermostatic valve that compensates for 20% changes in supply pressures to maintain a desired output temperature and also compensates for fluctuations in inlet supply temperatures. When the valve senses decreases in cold temperature, for example, it will adjust the incoming hot water to maintain the desired temperature.
The second type, a pressure-balanced Type P shower valve, senses changes in the incoming pressure. These valves are engineered to respond to 50% changes in water pressure in five seconds or less to maintain the correct output temperature within +/-3.6ºF.
The Type T/P combined thermostatic and pressure-balanced shower valve is the final type. This is a single valve that has to meet both temperature and pressure requirements. Previously, Type T/P valves needed two mechanisms: one to respond to temperature, and another for pressure. Technological improvements have produced valves capable of meeting and exceeding temperature and pressure requirements of ASSE 1016. The Type T/P valve now uses a single mechanism to meet the dual listings of the T and P valves, which is more cost effective than having two different devices.
The Type T/P valve is an emerging market. More specifications are calling for these valves, and demand for these products is on the rise. One reason for T/P valves’ rise in popularity is safety. A combination shower valve that is listed to Types T and P is more capable of providing the highest level of protection for end-users against harmful temperature and pressure fluctuations.
Another reason is maintenance, or lack thereof: Master mixing valves in the field are sometimes not maintained properly. An ASSE 1017-listed master mixer is typically the first valve used to temper water from the boiler as it goes through a domestic hot water loop to showers and lavatories. If that master mixer is not maintained regularly, it may impair the integrity of the valve and prohibit it from performing properly. Although in principle, a facility has multiple valves operating to safeguard people in different instances, individuals could still be exposed to poorly tempered water conditions if valves are not maintained properly. A T/P listed shower valve is a viable last line of defense for end-users.
ASSE 1017: Scalding and Legionella protection
The dangers of scalding are commonly known, and the IPC addresses scalding prevention by stating that shower and combination valves need to be equipped with a means to limit the temperature setting to 120ºF. City or state ordinances may differ for nursing homes and other specialized facilities. In these settings, code variations often push this limit down to the 105ºF-115ºF range.
For ASSE 1017 master mixers, there are different temperature tolerances to which valves need to adhere, depending on the amount of flow through the valve. For valves that are 3-5 gpm, the permissible temperature variation is +/-3ºF; for 5-40 gpm valves, it is +/-5ºF; and for valves in excess of 40 gpm, the range is +/-7ºF. Maintaining the tightest possible temperature tolerance range is important to protect individuals. Especially when the facility is experiencing low system demands, it is critical to offer end-users the tightest possible tolerance to safeguard them from exposure to thermal shock.
Plumbing engineers, however, should also be concerned with Legionella. Legionnaire’s disease is a type of pneumonia bacteria that is present in many water systems. To help combat this deadly disease, typically boilers and other hot water sources store water at 140ºF to kill Legionella bacteria, as it dies after 32 minutes of exposure. Because this water is much too hot to send through the system, facilities need an ASSE 1017 master mixer to temper water to a safer temperature (in the 120ºF range).
The 2009 IPC has put forth stricter regulations for protecting the public, and numerous mixing valves have advanced technologically to the point where they can provide better safeguards.
Peter Gobis III is the national sales manager for Leonard Valve Company in Cranston, R.I., which has manufactured thermostatic water mixing valves since 1913, Leonard Valve Company has been the quality leader in the manufacture of thermostatic water mixing valves. For more information, call (800) 222-1208, e-mail: info@leonardvalve.com or visit: www.leonardvalve.com.