Welcome to the site.

I noticed you posted the same question in two different sections. As an FYI that's not necessary.

Now to your question. Before I "re-piped" my system and added shut off valves I used a 1 1/2" rubber plug in my skimmer to plug it up. Just remove the basket and install the plug. This keeps the water from rushing in through the skimmer.

Again, welcome and enjoy your stay.