As usually happens on this forum a situation will be discussed and then something similar happens to one of us. We had a cracked 3/4" main line that supplies a planter near a cafeteria building (very old school) that is on domestic water and is hooked into the cafeteria water somehow. We were unable to find an isolation valve and turning off the cafeteria (even for a short time) was not an option so I had to make the repairs "hot" so to speak. We dug a large enough hole that we could set up our Honda pump to handle the water and then I glued in an open PVC ball valve. After letting it set up for about 15 minutes I was able to shut it down and reconnect the line. Here's some pictures. Please excuse the primer/glue mess. I had to work between pumping surges and wanted to make sure there was plenty on the pipe and fittings.