If you're feeding it from a regulator or manifold with one of those quarter turn valves, it already has a check valve. I'm talking about these valves: https://www.amazon.com/Learn-Brew-Threaded-Shutoff-Check/dp/B00RJBEH5M/ref=sr_1_6

If you're not, and you don't want to add one of those, then you'll need to account for the backpressure your check valve adds to the wetting pressure.

For example, my carb stones have a wetting pressure of about 5 psi. With the additional check valve, it will be more. You measure the wetting pressure by putting the stone in a bucket or jar of water and adjusting the pressure until you have a good curtain of very fine bubbles coming from the stone. Then note that pressure when you calculate how much pressure to set the stone to.