Top tips for inspection of cold water storage tanks

An annual inspection of cold water storage tanks is required to record the condition of the tank and the water within it.  It is also a requirement to check the temperature of stored water during the summer to ensure it remains below 20°C.

A trained Water Hygiene Technician must inspect the cold water storage tank and record the condition in the monitoring log book.  Any non-compliances are escalated in accordance with the chain of command stated in the control scheme and remedial actions carried out to ensure the tank remains in good condition within an appropriate timescale.

An inspection includes a check of both the inside and outside of the tank and the water held within it.  The lid should be tightly fitting and in good condition.  The insect and vermin screen on the overflow and warning pipes must be fitted and also in good condition.  The tank must be lagged which will help to maintain a constant temperature of the water and prevent it getting too warm or cold.  The surface of the water must not have a biofilm or show signs of stagnation.  The inlet and outlet of the tank should be opposing to also prevent stagnation.

Figure 1 below taken from page 26 of the HSG274 demonstrates the condition of cold water storage tanks and when action should be taken.  This traffic light system indicates actions to be taken and also the time frame in which they should be completed. 

Figure 1: HSG274 Legionnaires’ Disease p26

Regular tank inspection are an important part of a legionella control scheme because by preventing the habitat in which legionella bacteria can grow and proliferate you are ensuring the system will not provide the conditions suitable for harbouring legionella bacteria so therefore keeping your water system and ultimately your people safe.