Hi Steve, we're still only changing our GAC every 3-5 years i reckon.
Fraser, I was speaking to a Veolia engineer recently who said that those with low levels of water conductivity in their feed water like us (80-120uS) always have higher chlorine than those with the higher feed water conductivity.
Maybe because our water is soft and from reservoirs rather than bore holes it needs more disinfecting??
Manchester University NHS Foundation Trust