We use check valves on systems with auto chlorinators. If placed between filter and chlorinator they prevent high doses of chorine from getting back into the filter and causing damage. I was not aware of other needs, not to say there aren't.

Since most multi port valve assemblies have an closed position, the skimmer to pump hose is the most important place for a shut off valve. If you have PVC or flex PVC get a valve with slip openings on each side. The line can be cut anywhere and the valve glued in. If your pool uses regular pool flex hose they make a valve that has threads on one side (to screw into your hair and lint pot) and the other side is a hose adapter for using your existing pool hose.

Other options, if the opening at the base of your skimmer is threaded you can get a 1 1/2" MA and about a foot of PVC pipe and glue them together. When it is time to clean the basket, screw this fitting into the skimmer and turn your filter valve to closed.

If your fitting is not threaded, a tennis ball works good.

I could go on and on but I won't. I have seen, and done, a lot of different things to avoid installing those shut off valves.

Dennis