Need an app to turn a water valve on and off

looking for an app that will allow me to tun on a valve and turn off

What is the device mfg/model? When you say “an app”, what are you referring to? Presumably, since you are posting in the ST community, you would like to control the valve with ST, correct?

I don’t even know what ST is?
the valve is a Bonomi-M8E07-00
with an electric actuator that takes 120V. customer wants to operate the valve through an app on his phone.

ST stands for SmartThings™, which is a Home Automation platform from Samsung. This forum is for people using that platform, so all of the questions and answers are assumed to be in that context. It’s not a general Home Automation forum.

It sounds like you might get more helpful answers If you went to a forum that covers all brands, like the Reddit Home Automation subforum:

Make sure you tell them what country you are in, as the device and app options do vary by region.