Tanks and water pipes in Ships and Airplane are subject to the growth of bio-film arising from infected water. Once the bio-film takes hold it will infect further water introduced in to the tanks or pipes regardless of the quality of that water.
A bio-film is a matrix of bacteria attached to pipes that continues to grow and multiply. This Biofilm is resistant to chemicals.
For this reason tanks and pipes should ideally be cleaned out. After cleaning and where access is restricted this may be accomplished with either a strong Aquatabs / Klorsept shock dose (50ppm) or by allowing a 200:1 vinegar to water mix stand in the tanks and pipes for a minimum of 4 hours but ideally for 24 hours.
The procedure to follow is to introduce the solution to the tanks and pipes and then in succession turn on all taps until the smell of the solution indicates the arrival of the shock-dose or vinegar mix at the tap point. The tap is then turned off and the mixture is allowed stand in the pipes.
Once the stand time is complete all taps should be again turned on to ensure good flush-through of microscopic biofilm globules which have become detached.