Simple question regarding a switch

well, for you guys it is. To say I'm not electrical is an over statement...

I want to 'insert' an off/on switch before an existing outlet. [Just so you know, it is to toggle a March pump.]

I think I understand that I want to actually insert the switch on the hot leg leaving the common in place??? Or, does it matter if I connect (insert the toggle switch to either side?

So, which is the hot leg? Does it normally connect to the 'larger' side of the three-prong? Or, do I need to connect the electronic device and plug in a multimeter to get (what?) reading to be sure I'm inserting my toggle switch on the correct leg?

Thanks for your help!

Normal house wiring is Black for hot, white for neutral and green or green with a stripe for earth ground. You should use the hot side for your switch and use an SSR or relay to insure you have an adequate amount of amps and volts available. Most househols outlets are on a 15 Amp circuit, so keep that in mind when you start adding more stuff to your system. Hope this helps get ya going. Feel free to ask for help if you need more.
Wheelchair Bob

I should have made clear that the outlet is on a control box and inside both common and hot are white.

So, if I plug in this controller and measure the outlet via multimeter, what readings insure hot...positive or negative voltage?

Also, does it matter if I switch common vs. hot?

Always switch hot.

As above, always switch the hot lead. On a cord, the hot lead is the narrower of the two flat leads, the ground is the round lead. With both leads the same color, use an ohm meter to find the hot lead of an un-plugged cord.

Thanks!

If trying to find which is the hot leg, the multimeter will read 120 volts between the hot and neutral, AND the hot and ground. neutral and ground will not read voltage.

Perfect! Thanks

On a receptacle the brass colored screw is the "hot" and the silver is the neutral. And as was said always switch the hot.