Cutting into an existing water line under the floor:
There will be times when you need to cut into an existing line under the floor or up in the ceiling space. Or coming down into a wall from above which will have to be branched into to keep other fixtures alive with water.
In these cases if the pipe is galv begin near an existing threaded joint and cut with a 24-teeth to the inch hacksaw or sabre saw through the pipe to be branched into with your poly tee. Your cut about 3-foot (1 M) away from the chosen joint. Take a large plumbers pipe wrench and screwing anticlockwise wind the pipe out of the joint being careful to hold against this leverage with a second wrench on the socket next to you to be maintained at all cost in tact. And then screw out the other section of pipe remaining out of the next joint by sliding yourself near to this joint.
If the second joint is not available due to distance etc. Use a galv repair coupling. Simply slide the big nut and flange and the large rubber seal over the cut end of the pipe along with the body of the repair coupling. Then do the same on its other end with a 4-inch (100 mm) brass barrel nipple and tighten both at the same time. Then use a standard straight brass to poly coupling adaptor fitting and bridge the gap with poly pipe now placing your tee junction where you want it. Crimp all poly joints.