Locate the main water supply to the building, along with the cold and hot water lines. There is a separate line to the water heater and another line feeding the cold water faucets.
Close the main water valve feeding the building.
Cut the line before it splits off to the water heater if the entire building is to receive soft water. Use pipe cutters or a hack saw. Cut about an 8 inch piece out of the pipe.
Attach elbows to each end of the pipes where the piece was removed. Use solder if the pipe is copper or the proper fittings, if another type pipe is used, such as PVC or galvanized pipe.
Install a shut off valve on the pipe that is coming from the main water supply.
Install a U shaped loop onto the fittings or elbows where the original pipe was cut out. This loop can be removed when the water softener is installed if it is done at a later date. Build the loop using the same type of pipe used that was cut out. Solder copper if copper pipe is used. Glue fittings if PVC is used. Use threaded fittings if galvanized pipe is used.
Go back to step 3 if the water softener is only going to feed the hot water faucets in the building. Install the loop after the line splits so that only the hot water receives soft water.
Open the main water supply valve and check for leaks.