How to make a sump pump battery backup

Updated July 20, 2017

Sump pumps are used to pump flood water out of basements or other low-lying rooms in your residence. Sump pumps are typically run off electric power. However, it is not a bad idea to have a battery-powered backup for your sump pump. There are a number of battery-powered sump pump backup systems on the market. One of the more popular systems which can be made and hooked up to your existing electric sump pump is the Basement Watchdog.

Turn off the power to your existing electric sump pump.

Saw a 3 to 4 inch section of the existing sump pump's outflow pipe. Attach the two straight ends of the PVC Y-connector to the section of PVC you removed from your existing outflow pipe. Apply PVC glue to both straight ends of the connector and install it by hand.

Apply PVC glue to one end of a 1 foot length of straight PVC pipe and insert it into the Y-end of the Y-connector. Glue the other end of the straight piece of pipe coming from the Y-connector and place a 45 degree PVC elbow on it.

Apply PVC glue to a PVC adaptor and attach it to the connector on your Watchdog backup sump pump. Cut a 4 foot piece of straight PVC pipe and attach it to the connector on your Watchdog. Place your Watchdog backup pump at the bottom of your sump pump pit. Do not allow it to touch your main sump pump.

Drill a small hole at an upward 45 degree angle on the pipe about 3 inches above where the PVC pipe attaches to the sump pump.

Using a screwdriver, install the check valve between the end of the 4 foot pipe and the 45 degree elbow. Make sure the arrows on the side of the check valve are facing up when you install it or it will not prevent backflow.

Attach the wire running from your Watchdog to the side of the pipe with a piece of tape or a metal clamp

Open the battery case by pressing in on the front tabs and lifting it. Set the battery into the battery box several feet away from your sump pump pit.

Push in the tab on the top of the acid pack and pull the dispenser hose out. Clip the end of the dispenser hose off and fill the six cells of the battery with the acid.

Secure the float switch to the PVC outflow pipe with a plastic tie. Plug the pump wires

into the pump connector on the back of the Watchdog's control unit.

Remove the cap on the second battery cap from the positive battery post. It will be clearly marked. Insert the yellow battery cap and then place the end of the fluid sensor into the hole on the top of the cap that is off-centre.

Remove the wing nuts on the battery terminal posts and then connect the positive (red) wire to the positive terminal and the negative (black) wire to the negative terminal post of the battery.

Close the cover of the battery box and then plug one end of the AC charger into the back of the control unit and the other end into your wall AC outlet.


Do not walk on wet areas of your basement until all the power has been turned off. To avoid electric shock, never handle the control unit with wet hands or when standing in or near water. Charge your battery in a well-ventilated area.


Don't use automobile batteries, or sealed (or maintenance-free) batteries with this system. Also, when you fill the battery the first time, this will be the only time you fill it with acid. In the future, when you check your battery, add distilled water when it is low. Always shield face and eyes from battery, especially when handling the acid. Wear eye protection and don't touch your face while working with the battery. If battery acid contacts skin or clothing, wash immediately with soap and water. If acid enters eye, flush eye with running cold water for at least 10 minutes call a doctor.

Things You'll Need

  • PVC saw
  • PVC Y-connector
  • PVC glue
  • PVC connectors
  • PVC elbow
  • Tape
  • Plastic tie
  • Screwdriver
  • Basement Watchdog backup system with battery
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About the Author

Ashton Daigle, a New Orleans native, graduated from Southeastern Louisiana University in 1998 and went straight to work as a journalist. In 2005 he tackled the biggest news story of his life - Hurricane Katrina. Daigle is writing a collection of essays: What It Means to be a Saints Fan.