Norwegian bath anti-scald valve Guide to Point-of-use & Plumbing Fixture Anti Scald Valves

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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.

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Point of Use & Plumbing Fixture Anti-Scald Valves

Guide to Bath Fixture Anti-Scald Valves, Automatic, Thermostatic Mixing Valves, or Tempering Valves to Avoid Hot Water Burns

Norwegian bath anti-scald valve

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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.

Figure 6-1: Accessible Kitchen Design Specs: accessible sink and dishwasher work centers (C) J Wiley S Bliss

[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

Sparco tempering valve (C) Daniel Friedman

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 sink faucets.

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 shower control.

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 below 120°F.

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.

At TANKLESS COIL INSTALLATION PROCEDURE where we recommend the use of mixing valves we quote this warning from the Crown Boiler Company:

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]


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)

Anti-Scald & Hot Water Safety Articles


Continue reading at POINT of USE ANTI-SCALD WATER TEMPERATURE ADJUST Pfister or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



If your hot water temperatures are too low, see TEMPERATURE of HOT WATER is TOO LOW

If you do not have enough hot water pressure or hot water quantity, see HOT WATER QUANTITY IMPROVEMENT

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