When it comes to potable mains drinking water the most critical threat for people are pathogens that are present in the water. They can enter the system as we drink the water and can bring about a range of diseases, some of which can be life threatening.
Most drinking water is treated with chlorine at source by the water company to ensure that it remains safe for consumption. However, once it leaves the water treatment plant no further disinfectant is added and as such the distribution pipe work has to be kept clean and micro organism free in order for the drinking water to reach the end consumer safely.
Any new pipe, repairs or refurbishment pipe work connected to the existing mains supply network needs to be clean and contaminant free in order to guarantee cleanliness of the present network. If contaminated water line is added to the current network it has the possibility to contaminate the whole system, potentially inflicting illness in lots of people.
As such all new pipe work must be disinfected before use. The principle of this procedure is to introduce chlorine into drinking water, the most common chlorine releasing compound being sodium hypochlorite. When this is added to water chlorine is released and this chlorine is a strong oxidant which can rapidly destroy all living cells. The procedure utilised for new pipe work is referred to as chlorination and utilises this chlorine at 50 ppm in place for at least 1 hour to kill all harmful micro organisms. The system is then flushed through with clean water and sealed to prevent further ingress of bacteria and dirt.
Any company carrying out work such as a new mains chlorination should possess the appropriate health and safety training and all staff should have the Blue Water Hygiene Card. This is a training course developed for operatives working on potable water supplies to make sure they are familiar with the issues of contamination and the dangers involved.
All work carried out must provide a chlorination certificate from the company carrying out the work and this must include such elements as date, pipe dimensions and volume, chlorine level, contact time and end chlorine amount after flushing. Microbiological analysis of the drinking water inside of the chlorinated pipe work should also be performed to make certain that no microbial contamination of the water pipe remains.
After the chlorination process has been performed and the bacterial analysis has arrived back clear the new water pipe may be linked onto the existing water network.

Get extra info on chlorination to determine if you require a chlorination certificate for your water pipe work.