Not sure what "lifetime" plastic valves are, but I have a couple of suggestions:

#1 When you remove those brass ball valves (worth about $10 scrap, right now!) make your new connection with a male/female threaded pair. That way, if you have to work on the lines in the future, you simply unscrew the part above ground. You can use RTV silicone as a thread sealant, if you like. Or, since they are suction lines, you can use Teflon tape, and the if you have a bit of a suction leak, you can use silicone to fix them -- the suction will pull the silicone into the threads and stop the leak permanently.

#2 Make SURE your valves are full port valves - that is that the opening in the valves is as large or close to it, as the opening in your pipe. Looks like you have 1.5" ID pipe, so you are looking for valves with a 1.5" port.

Ben