How to Add Distilled Water to Sump Pump Batteries

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Things You'll Need

  • Safety glasses

  • Rubber gloves

  • Paper towels

  • Slotted screwdriver (optional)

  • Distilled water


The acid contained in the battery is highly corrosive and can also be extremely flammable.

Do not expose the battery to any open flames as the fumes from a charging battery are highly explosive.

Follow the battery manufactures specifications for keeping the batteries in a well ventilated area.

Sump pump batteries are used as emergency backup power to the pumps. Different types of batteries are employed for the backup power. Most typically a deep cycle battery is used, which is not the same as a regular car starting battery. Maintaining these batteries is crucial to the longevity of the backup power source. Keeping the water level at optimum is key to a well performing system. Only unsealed batteries can have distilled water added to the separate cells. Sealed batteries are identified by not having removable caps on the top of the battery.

Step 1

Place the safety glasses and rubber gloves on your body to protect yourself from any possibility of spillage from the acid water mixture. Remove all electrical power from the charging system to the battery. In most cases this is simply pulling the plug from the AC charger that feeds the battery.

Step 2

Clean the top of the battery with a paper towel. Discard the towel immediately as it might contain dried acid.

Step 3

Remove the caps of the battery. Various unsealed batteries may have different caps. Individual screw on caps will cover each separate battery cell, which will be six in total for one battery. Unscrew the separate screws caps and set to the side. Use the slotted screwdriver to pry off the caps if they are part of an assembly. Most typically these pry off caps will cover three cells. There will be two caps for one battery.

Step 4

Observe inside the openings of the battery. There will be a plastic ring that extends down inside each cell. Check the fluid level of each cell. The fluid height must be kept to just below the level of the interior ring.

Step 5

Add just enough distilled water to raise the fluid level to the height of the lower end of the interior plastic ring. Replace the caps on the battery. Thoroughly wipe the top of the battery dry with the paper towels. Reenergize the battery charging system.

references & resources

G.K. Bayne

G.K. Bayne is a freelance writer for various websites, specializing in back-to-basics instructional articles on computers and electrical equipment. Bayne began her writing career in 1975 and studied history at the University of Tennessee.