DESIGN ALERT ON DOMESTIC WATER HEAT ER
TEMPERATURE
ISSUE:
Scald protection for patients and staff from domestic hot water systems.
BACKGROUND:
As a result of the recent unfortunate scalding accident at a VA facility, a number of
questions have been asked regarding the design of domestic hot water system and
control of hot water temperature at the fixture outlet.
DISCUSSION:
Concern over accidental scalding of patients and staff by domestic hot water has been
a key issue the design of VA domestic hot water systems for some time. These
concerns are reflected in the design guidance that has been developed by CM in
consultation with the field. The most recent significant changes, related to this issue,
were in 1990. At this time domestic water temperatures were raised due to concerns
related to Legionnaires Disease. Previously, water temperatures were 120 degrees F
from the heater and 110 degrees F at the farthest plumbing fixture, these temperature
were raised to 130 degrees and 120 degrees respectively. To reduce the potential for
scalds, a thermostatic mixing valve at the fixture is required and was added to the
specifications. This valve controls the shower and tub fixture temperature at 105
degrees F, preventing burn or scald injuries.
VHA Directive 10-95-?, Domestic Hot Water Temperature Limits, is in the final stage of
development and should be issued shortly by Clinical Programs (111A). This directive
provides guidance concerning temperatures related to Legionnaires Disease, scalding,
and energy. It will replace VHA Directive 10-93-155.
"Semi-instantaneous" type water heater are recommended in current VA design
manuals and are the only water heater systems specified in VA Master Specification
15424, Domestic Water Heaters. They require minimal space, provide accurate,
consistent control of outlet temperature, and minimize problems due to fouling.
"Instantaneous" type water heater were specified as an option several years ago, but
were deleted because of outlet temperature control and increased potential for scalding
problems. The instantaneous heaters use a blending valve to provide the correct
delivery temperature and requires engineering personnel to monitor the temperature
and make seasonal adjustments. It also requires a master thermostatic mixing valve
and temperature alarms to reduce the potential for accidental scalding.
12 June 1995
FM-187C/088-DA37
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