I have tap water at around 250ppm. I fitted a pumped RO unit and the reading was 0ppm for around 1000L. This has now shot up to 74ppm and I have only produced only about 3000L of water so far. Obviously I have a DI vessel so this is 0 in the tank but I am concerned by how fast it shot up to 74ppm. Is this normal? will it continue to rise quickly?