The achievable flow rate is an important factor to consider when specifying an emergency shower. The ANSI/ISEA Z358.1-2014 which is the American standard that relates to emergency showers and eyewashes states that an emergency shower must be able achieve a minimum flow rate of 75.7 liters per minute for at least 15 minutes, the European standard (EN15154) is a similar specification: 60 lpm again for 15 minutes. These flow rates are necessary in order to deliver a sufficient volume of water in order to dilute any substances that can cause serious damage to the tissue of eyes and skin such as concentrated caustic soda for example.
Usually these high flow cannot be achieved from mains water sources alone, even in industrial settings. The water sources can also often be intermediate in many industrial environments making it difficult to guarantee the safety of employees using a mains fed tubular shower. A tank shower offers reliability in any environment, storing the required volume of water in an overhead tank and delivering the necessary flow rate using a dependable gravity fed system.
The need for tepid water (16-38°C ) is often a requirement that gets overlooked during the procurement of emergency showers with many facilities installing tubular showers with a direct feed from the cold water supply. This can actually pose a serious health and safety for the operatives on site. Many COSHH data sheets for caustic substances recommend rinsing exposed skin under water for between 10-15 minutes and with the average mains water temperature being only 6-7°C the risk of hyperthermia when exposed to water at these temperatures for a prolonged period of time is very high. Not only can cold water result in shock or even pneumonia, it also increases the likelihood of any operatives leaving the shower prematurely leading to more risk of long term tissue damage.
It is certainly possible to achieve tepid water with a tubular shower by mixing the cold mains water with some stored hot water using a thermomixing valve capable of handling the high flow rates required. However the more straightforward solution which requires less infrastructure setup is to use a tank shower which has an internal heating element that keeps the water at the correct temperature between 16-19°C.