How much chlorine is in my water?

The way we disinfect drinking water is to add tightly controlled amounts of chlorine at our water supply works. A small amount of chlorine remains in the water after treatment. This ‘residual’ amount of chlorine ensures that the water stays bacteriologically safe as it passes through the distribution mains. 

In very long distribution networks, we sometimes add chlorine at strategic points. This helps us ensure there is enough throughout the whole length of the system. We call this 'boosting'. These residual amounts of chlorine are also monitored at the water supply works, service reservoirs and customer taps using field monitoring kits.

Residual levels of chlorine are harmless to domestic pets but can affect fish and amphibians such as frogs and turtles. Fish kept in aquariums or ponds are also extremely sensitive to chlorine.

When you’re filling or topping up aquariums, you should try to remove the chlorine before water comes into contact with the fish. Aquatic and pet shops can offer suitable products and advice to do this.