The right mixing valve in the right place

Every year in Quebec, on average three people have a fatal accident caused by the hot water in their bath or shower, and 33 others are hospitalized (6). One of the possible solutions to avoid this tragedy would be the installation of a mixing valve. This article deals with what a mixing valve is, the different types as well as their use, their risks and their maintenance.

The function of mixing valves is to adjust and to maintain the water at a predetermined and constant temperature and flow.  The mixing valve mixes hot and cold water according to the preselected temperature.

Mixing valves offer several advantages such as:

• Comfort: Mixing valves regulate the flow and temperature of the water almost instantly according to the user's needs. (4)
• Economy: Since the water temperature is always controlled, the mixing valve saves water and energy.  (2)
• Safety: The mixing valve keeps the water temperature constant and thus avoids the possibility of thermal shocks.  (1)

The two most popular types of mixing valves on the market are the thermostatic and the pressure-balanced mixing valves. Both have advantages as well as disadvantages. 

To meet the requirements of health and safety standards, emergency showers are equipped with a thermostatic mixing valve with certain features such as maintaining the temperature in the required interval and have anti-scalding protection. The thermostatic mixing valve is also used in the Long-Term Care Hospital Centers (CHSLD).  However, specialized thermostatic mixing valves are mainly used for emergency showers (5). They adjust the flow rate and temperature immediately and keep them stable for the desired duration.

Pressure-balanced mixing valves are used less since they adjust more slowly to the desired temperature (2), however, they are less expensive. One of the disadvantages is that they are sensitive to pressure variations.

In CHSLDs, it is possible to install a pressure-balanced and thermostatic combined mixing valve to meet the requirements of the Safety Code of the Régie du Bâtiment du Québec (section 7.3).

Several dangers can occur with poor selection or the absence of mixing valve:

• Thermal shock which can cause burns. In addition, sudden changes in temperature can lead to other injuries, ex. sliding in the shower (1). Several models of mixing valves have a safety feature that cuts off the flow of water when there is a lack of hot or cold water in the feed (5).
• Hot water burn. Children, the elderly, and the disabled are most vulnerable to severe burns caused by extreme hot water (2).  Burn incidents can occur at home as well as in commercial or institutional facilities.
• Diseases caused by waterborne bacteria such as Legionellosis. This bacterium thrives in stagnant water between 20°C and 45°C. This is why hot water reserves must be maintained at 60°C (3). However, this temperature is too high to be used, so the mixing valve decreases it. 

In conclusion, in order to improve the well-being, health and safety of users, companies will always consider the use of a thermostatic mixing valve since they offer more safety. When the thermostatic mixing valve is used for an emergency shower, it must be selected for that specific use in order to meet health and safety requirements.

(1) Prévention des cas de brûlures et de légionelloses liés à l’eau chaude du robinet | Bulletin d'information en santé environnementale | INSPQ

(2) Qu'est-ce qu'un mitigeur thermostatique - Tendances & Design - Salle de bains | GROHE

(3) Le mitigeur de douche : les différents types, entretien, achat, choix (m-habitat.fr)

(4) Thermostatic Mixing Valves

(5) 9201EFE - Thermostatic Mixing Valve - Haws Co

(6) *RBQ - Code de sécurité - 2021.pdf