I guess it depends on how your system is setup. I have one that turns on my ATO pump because I have a manual valve I can switch to make the fresh RODI water come out a faucet instead of going into the sump. So I turn the valve then push that momentary switch to collect RODI in a container for use with various things like mixing 2-part, cleaning salt creep, etc.
I also have one for the return pump. In case of emergency like an overflowing tank or leaking, I can quickly shut off the return pump that way.
