If you see a low ORP number, yet you have a high Sanitizer(Bromine or Chlorine) PPM, you likely have one of two scenarios taking place.
The first is that stabilizer blocking your sanitizers ability to do its job. Cyanuric Acid is often used as stabilizer to prevent chlorine burn off in pools. Typically, Hot Tubs and Swim Spas won't have to worry about Cyanuric Acid, since they have covers or are indoors. However, there are sanitizer chemicals that automatically add Cyanuric Acid(stabilizer) to your water. Dichlor and BromoChlor both contain Cyanuric Acid and if used as a sanitizer, will require you to have higher than normal levels. Ideally, your sanitizer PPM will be 11% of what your Cyanuric Acid(CYA) levels are. This will allow your sanitizer to do it's job in removing pathogens, bacteria, algae adn other microoganisms.
Another scenario as to why your ORP might be low is that your pH levels are simply too high. This is often the case with saltwater pools because their pH level is always climbing. We recommend keeping your pH level around 7.4 so your sanitizer can be more effective in its fight.