Guide to Point-of-use & Plumbing Fixture Anti Scald Valves
POINT of USE BUILT-IN FIXTURE ANTI-SCALD VALVES - CONTENTS: What are point-of-use mixing valves - anti-scald valves located at or built-into plumbing fixtures such as tub or shower controls: automatic temperature compensation valves to avoid scalding burns
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Point-of-Use or plumbing-fixture built-in anti-scald protection for hot water systems:
This article describes the safe regulation of hot water temperatures right at the plumbing fixture, either by a separate hot water temperature controller or by a hot water temperature control or anti-scald feature built right into the plumbing fixture valve used at sinks, tubs, and showers. These point of use or POU anti-scald devices provide important hot water burn protection but may need adjustment if the hot water they provide is not hot enough or if it is too hot.
In these hot water anti-scalding burn articles we explain how to buy, install, adjust and inspect anti-scald equipment to prevent hot water burns. We explain what a mixing valve, tempering valve, or anti-scald valve is, where and why these valves are installed on hot water systems, and how they work.
Anti-scald valves that actually sense the water temperature are available built right into bathroom sink or shower fixtures, as you can see in our photo at left.
These devices permit delivery of very hot water to a building area but protect occupants from scalding by mixing in cold water right at the sink, tub, or shower.
As you can see on the control shown in our photo of a shower control in a shower-bath in Molde, Norway, fixture anti-scald valves may include a button and adjustment that lets the user demand hotter water than the control provides automatically.
On this bath shower fixture the left-hand control turns water on or off, and the right-hand control permits adjustment of the water temperature. Turning the temperature control "down" or counter-clockwise increases water temperature but the control "snaps" into a locked position at a safe hot water temperature of about 100 °F. The user can obtain hotter water by depressing a red button and turning the control further.
The point-of-use anti scald protection afforded by this type of pressure-balancing anti-scald valve is discussed further at Water Pressure-Balancing Valves.
How to Use Point of Supply Water Pressure-Balancing Valves to Control Temperature & Avoid Scalding
Use of Point of Supply or Point of Use Thermostatic Mixing Valves to Avoid Scalding Burns
Some models of thermostatic mixing valves are more expensive
than pressure-balancing valves and not widely used in
the United States. They can be installed either inline near
the water heater or as part of the shower control. The inline
type of valve, also called a tempering valve, adds cold
water to the hot water as it leaves the water heater to maintain
a constant temperature, set by the installer. These are
commonly used with solar water heaters but can also be
tied to a conventional water heater.
A check valve is
required on the cold water side to prevent backflow, and a
hot-water expansion tank is recommended to prevent
excessive pressure on the hot water side.
[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]
The other type of thermostatic valve is built into some high-end showers (Figure 6-54). These allow the user to set the temperature on a dial when showering.
The unit will compensate for changes in either pressure or temperature to maintain a constant delivery temperature and flow rate. If the cold water fails or the tempered water is still too hot for any reason, the unit will shut off the flow.
As with the
pressure-balancing valve, the installer sets a temperature
limit stop to prevent the user from turning the shower control
to scalding temperatures. We illustrate this approach as it is installed in a modern bathroom in Molde, Norway at Built-in Fixture Anti-Scald Valves.
Retrofits to Avoid Scalding Burns at Plumbing Fixtures
In retrofits, point-of-use devices can be
installed by a plumber or homeowner to limit water temperatures
to 120°F. These include antiscald showerheads,
as well as point-of-use devices that fit into individual
plumbing fixtures, such as showerheads and bath and
For example, MemrySafe and ScaldShield
(Antiscald Inc.) are inexpensive retrofit devices that
reduce the water flow to less than 1/4 gallon per minute when
the water temperature at the faucet or showerhead exceeds
120°F. These devices do not regulate temperature or pressure,
but do offer protection against serious burns.
This is the most commonly
used point-of-supply approach. These automatically
adjust the water pressure to maintain the mix of hot and
cold water to within 2°F to 3°F of where the user set the
If cold water is diverted to a flushing toilet
or other appliance and the pressure drops, the valve automatically
reduces the hot water flow proportionately to
maintain the temperature.
If the cold water pressure plummets
or stops altogether, the flow is reduced to a trickle.
To guard against someone accidentally turning the shower
valve to scalding temperatures, these valves typically use
a temperature limit stop that prevents the user from turning
the shower control past a set point—typically set at or
Anti-Scald Valve Point-of-Use Safety Warnings
Watch out: read the installation instructions from the manufacturer of the product you are installing, both to make sure it's installed properly and thus will work as expected, and also so that you understand what to expect by way of hot water temperature control the product handles.
WARNING: Thermostatic mixing valves are intended to increase the supply of hot water available from the coil. They are not intended to prevent a scald hazard.
Similarly, the Watts Regulator Company's instructions for the installation of the Series LF1170 & LFL 1170 Hot Water Temperature Control Valves includes this warning: [Bold font is our emphasis]
WARNING: FAILURE TO COMPLY WITH PROPER INSTALLATION AND
MAINTENANCE INSTRUCTIONS COULD CONTRIBUTE TO THE VALVE
This Hot Water Master Tempering Valves cannot be used for tempering water temperature at fixtures. Severe bodily injury (i.e., scalding
or chilling) and/or death may result depending upon system water
pressure changes and/or supply water temperature changes. ASSE
standard 1016, 1069 or 1070 listed devices should be used at fixtures to prevent possible injury.
These Hot Water Tempering Valves are designed to be installed at or near
the boiler or water heater. They are not designed to compensate for system pressure fluctuations and should not be used where ASSE standard
1016, 1069 or 1070 devices are required. These valves should never be
used to provide “anti-scald” or “anti-chill” service.
The components of the system must be of materials with a construction
capable of withstanding the high limit output temperatures of the water
heating source. - Watts (2013)
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"Instructions Series LF1170 and LFL1170 Hot Water Temperature Control Valves", Watts Regulator Co. (2013), USA Tel: (978) 688-1811, Fax: (978) 794-1848,
Website: www.watts.com, Canada: Tel: (905) 332-4090, Fax: (905) 332-7068, Website: www.watts.ca
"BDS Series Oil-Fired Hot Water Boilers, Installation Instructions, Models GS-080 -> Crown BDS-236", Crown Boiler Company, BDS 12-99, Crown Boiler Co.
P.O. Box 14818
3633 I Street
Philadelphia, PA 19134
Website: http://www.crownboiler.com, retrieved 2/26/2014, original source: http://www.crownboiler.com/manuals/content/ All_Models/BDS%20Series%20%28all%20models%29.pdf
The following link provides access to literature or manuals for previous Crown products:
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: firstname.lastname@example.org
 "Water Saving Tips: For Residential Water Use, Indoors and Out", Alliance for Water Efficiency, 300 W Adams Street, Suite 601 Chicago, Illinois 60606, Tel: 773-360-5100, 866-730-A4WE, Email: email@example.com, web search 12/14/11, original source: plumbingefficiencyresearchcoalition.org/
 "Danger in the Shower: 2008 Forum Looks at Hot Water", John Koeller, Home Energy, Jan/Feb 2009, Home Energy Magazine, 1250 Addison Street Suite 211B, Berkeley, Ca. 94702, Tel: (510) 524-5405 Email: firstname.lastname@example.org
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
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