Funny you mention that...I want to have valves at the end of the pipe, but I
have not seen any at Home Depot for the 4 inch pipe. Am I missing something?

Knife valves are the cheapest valve but hard to find in 4".

A threaded coupling and threaded plug on the end works, though
those get pricy too in 4", plus you get wet and can't reduce
the flow by half unless you drill the plug.

Just slipping a 4" cap over the end can work. Can be difficult
to remove.

Saran wrap with a rubber band is the low cost winner :-^