Tepid Water: Definition, Uses and Importance

Key Takeaways

• Tepid water is controlled within a temperature range of 60 to 100°F (16 to 38°C), and is commonly used in emergency showers and eyewash stations.

• Industries use tepid water to help reduce the risks of chemical exposure during cleaning or decontamination procedures.

• Tepid water temperature is recommended for treating minor burns and injuries because it avoids shock from cold water or damage from hot water.

• The tepid water meaning differs slightly from lukewarm and room temperature water.

What Is Tepid Water?

Tepid water is a flushing fluid that is neither too hot nor too cold. According to the American National Standards Institute (ANSI), an organization that governs the performance and installation of emergency eyewash and shower equipment, tepid water is defined as water with a temperature between 60°F and 100°F (16°C to 38°C). This specific range is designed to balance comfort and safety in emergency situations where temperature can influence how the body reacts to contamination or injury.

In an article, Ron George, CPD and ASSE 12080 Legionella Management Professional, who served on the emergency fixture working group for a standards-writing organization, explained how the term “tepid” came to be used for emergency equipment water:

It was pointed out that tempered water was defined in the plumbing codes as follows: “Tempered Water — Water having a temperature range between [85 F and 110 F.]” Since tempered water was defined in the plumbing codes with a specific temperature range too hot for use in emergency fixtures, the term could not be referenced in the emergency fixture standard. With a little help from a thesaurus, the term “tepid” surfaced with the following definition: moderately or slightly warm; lukewarm.

George noted that this definition was more appropriate, and tepid was adopted as the standard term for water used in emergency showers and eyewash stations. Tepid systems are designed to deliver flushing fluid that ensures individuals can endure the required flush duration without experiencing shock from cold water or burns from water that is too hot.

Is There a Difference Between Tepid Water and Lukewarm Water?

Tepid water is sometimes confused with lukewarm water and used interchangeably. But lukewarm water generally refers to a slightly narrower temperature range, centered around body temperature. This would typically be between 98°F and 105°F (36.5°C to 40.5°C), just a bit warmer than tepid water. There is also a difference between tepid water and room temperature water, which refers to water that has naturally adjusted to the ambient temperature of the surroundings and is often preferred for consumption.

What Is Tepid Water Used For?

Tepid water is used for a range of purposes depending on the environment or situation. Its moderate temperature helps reduce discomfort, improve safety outcomes, and encourage longer use when needed.

Industrial Use

In industrial settings, tepid water is often used for emergency eyewash and safety shower units. Its temperature range helps in mitigating the risk of thermal shock or chemical reactions that can occur with extreme temperatures. A 2017 study found that more than 43% of chemical burns happen in the workplace, with the majority of those incidents occurring in industrial environments. The same study noted that immediate, thorough irrigation with water or saline is the first step in treatment, and that using moderately warm water, such as tepid water, is often recommended to support that response.

Medical Use

In healthcare and first aid, tepid water temperature is frequently recommended for specific injuries and treatments. For example, it is used for cleaning wounds or in hydrotherapy to treat injuries. Tepid water is often recommended because it is gentle on the skin and less likely to cause additional harm to the patient. Cold water may cause vasoconstriction and increase discomfort, while hot water may worsen tissue damage.

Home Use

In everyday use, tepid water is often preferred for tasks that involve sensitive skin or require temperature control. When bathing infants, it helps reduce the risk of burns or cold stress. In personal care, particularly in skincare and hair washing, tepid water provides effective cleansing without disrupting the skin barrier or removing essential oils from the hair.

Importance of Tepid Water Temperature for Eyewash Equipment

The importance of tepid water temperature in eyewash equipment is primarily related to safety, comfort, and effectiveness during emergency eye irrigation:

Prevents Further Injury

Tepid water ensures that in the critical moments following an accident, first aid measures that flushing fluid do not unintentionally cause further harm, allowing for a more effective and safer response to workplace injuries.

• • Water that is hotter than 100°F (38°C) can damage sensitive eye tissue and increase the severity of the injury. High-temperature water can also cause burns, leading to pain, skin damage, and an increased risk of chemical absorption into the skin. 

  • Cold water below 60°F (16°C) can cause thermal shock. Discomfort may also make individuals reluctant to remove contaminated clothing, increasing their exposure time and raising the risk of hypothermia.

Encourages Full 15-Minute Irrigation

A continuous water flow for at least 15 minutes is required to thoroughly wash away hazardous chemicals from the skin and eyes. However, if the water is “too hot” or “too cold,” individuals may be unable to tolerate the full duration. Tepid water is comfortable enough to allow continuous flushing, as outlined in ANSI/ISEA Z358.1-2014. This uninterrupted rinse is critical for reducing chemical absorption and limiting injury until medical care can be provided.

Enhances Removal of Contaminants

Effective removal of contaminants requires thorough and uninterrupted rinsing for both eyes and skin. Tepid water temperature ensures that individuals do not involuntarily tense up or restrict the flow of water to certain areas. This supports more efficient removal of chemicals, debris, or biological hazards and minimizes the risk of residual contamination that could lead to more severe injuries or complications.

Compliance with Safety Standards

ANSI/ISEA Z358.1 specifies not only the duration and flow rate for emergency equipment, but also the provision of tepid water to ensure safe and effective use. If an employer fails to comply, OSHA can impose penalties. These violations fall under OSHA's scope because they are considered a part of providing a safe and healthful workplace, as mandated by the Occupational Safety and Health Act.

Tepid Water Requirements for Emergency Eyewash Equipment

ANSI/ISEA Z358.1-2014 defines tepid water as “moderately warm, lukewarm,” but the standard offers more specific guidance in Appendix B6. According to this section, 

Temperatures greater than 100°F have been proven to be harmful to the eyes and may enhance chemical interaction with the eyes or skin. Meanwhile, 60°F should be a suitable lower parameter for tepid flushing fluid without causing hypothermia.

This requirement ensures that the water used in emergency showers and eyewash stations is not so cold as to cause hypothermia or so hot as to scald the skin or aggravate chemical reactions. The table below outlines the specific criteria for eyewash and emergency shower equipment:

While OSHA does not specify temperature ranges for emergency eyewash and shower facilities, it does reference ANSI standards in its regulations. OSHA's General Duty Clause Section 5(a)(1) requires employers to provide a workplace free from recognized hazards. This includes providing appropriate emergency facilities, which, by industry best practices and ANSI standards, imply the availability of tepid water.

Challenges and Solutions in Tepid Water Delivery

Variations in climate, water supply, and facility design can all interfere with delivering water within the required temperature range. Let’s break down the practical solutions to some of these challenges: 

Temperature Fluctuations

In outdoor or unconditioned indoor areas, seasonal changes can cause water temperatures to fall below 60°F in winter or exceed 100°F in summer. This makes it difficult to maintain compliance and poses risks during an actual emergency.

Practical Solution: Installing thermostatic mixing valves (TMV) helps regulate water temperature in real time, blending hot water and cold water to consistently produce tepid water. Modern TMVs also include failsafe mechanisms that shut off flow if either supply line fails.

Inadequate Mixing Systems

Some older or improperly installed systems may lack TMVs, which are critical for blending cold water and hot water to maintain a stable tepid water temperature.

Practical Solution: For cold climates or exposed piping, electric or steam-traced piping and tankless water heaters can prevent water from dropping below 60°F. These systems are often paired with insulation and temperature sensors.

Remote Locations

In facilities with large or spread-out operations, such as refineries, mining sites, or shipping terminals, delivering properly tempered water to remote stations.

Practical Solution: Recirculation systems help keep water moving continuously through supply lines to maintain temperature and reduce stagnation. They are especially useful for meeting ANSI requirements in large facilities.

Water Stagnation

Infrequently used stations can suffer from stagnant water in pipes, leading to delayed temperature stabilization and increased risk of contamination.

Practical Solution: Weekly activation and routine temperature inspections help ensure each eyewash station functions correctly and delivers water within the proper range when needed.

FAQs on Tepid Water

What does tepid water mean?

Tepid water refers to water controlled within a fixed temperature range of 60 to 100°F (16 to 38°C). It is commonly used in safety, medical, and hygiene applications where extremes of temperature should be avoided.

Which is warmer, tepid or hot water?

Hot water is warmer than tepid water. Tepid water falls below the typical hot water range, which usually starts at around 110°F.

Why is tepid water recommended for flushing the eyes and skin during emergencies?

Tepid water allows for a more comfortable and sustained 15-minute flush, as required by safety standards. Water that is too cold or hot can cause further injury or discourage proper decontamination.

How do I get tepid water?

Tepid water can be delivered using thermostatic mixing valves that blend cold water and hot water to maintain the desired range. In some cases, tankless heaters or recirculating systems may also be used, especially in industrial or safety settings.

Are there any regulations or guidelines regarding tepid water in specific industries?

Yes, ANSI/ISEA Z358.1 provides specific requirements for tepid water temperature in emergency showers and eyewash stations, and OSHA refers to these standards in its enforcement of workplace safety. These guidelines ensure that the water temperature remains within a safe and comfortable range for users in case of emergencies.

Can I drink tepid water?

Yes, tepid water is safe to drink as long as it’s from a potable source.