How to Read the Indicator Eye

Many people incorrectly interpret the status of the indicator eye to mean "I need to water my battery". These notes explain how to "read" the valve indicator eyes on a battery.

  • Do not look at the indicator eyes if the batteries are not fully charged. The charging process changes the electrolyte level in a battery. The electrolyte level will be significantly higher in a charged battery versus a discharged battery. This is why you are always instructed to only water a fully charged battery. The indicator eyes on a discharged battery will be down even if the battery has exactly the correct amount of electrolyte.
  • Do not water based only on an indicator being down. Watering should be done based on usage. In a typical fleet application, watering twice a month is sufficient and certainly no more than once per week. A residential user should not need to water more than once a month.






Look at all of the indicator eyes. You can tell something about the system from the state of the indicator eyes before watering.

  • If all of the eyes are down except for one (or two) and one or two have the indicator fully up, pull the valve out of the vent well and check for interference with the float, free movement of the valve mechanism and water in the cell.
  • If all of the eyes are up or mostly up, your battery may not need watering. Make sure you are not watering too frequently.
  • You would expect the indicator eyes to be down or mostly down after a couple of weeks of use. 




During watering, the flow indicator should be turning.

  • Watch the indicator eyes. They should pop up at various times during the watering cycle depending on how much water each cell needs. When they are all up, the flow indicator should stop.
  • If all of the indicators pop up immediately after starting the watering process, you may have a pressure issue.
  • Make sure the pressure regulator has not been removed if you are using the watering gun or direct fill link. The valves will not operate properly if the pressure regulator has been removed. 



  • When the flow indicator stops, all of the indicator eyes should be up.
  • It is not unusual for the indicator eyes to drop slightly after the delivery system has been disconnected. Water pressure tends to hold the float slightly higher than its natural buoyancy level. Seeing a slight drop also confirms that there are no interferences with the float's operation.
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