Leaky out post on keg?

Is there any way to fix this? When i put water in it and give it some presure the out post shoots out water? I have another keg that is a cornelius keg (this one is firestone). Are these out posts interchangeable?

There is a poppet inside the post and an o-ring around the tube that goes to the bottom. If the water comes out the center of the post, your poppet is bad or not seated properly. If it comes out around the edges where the post attaches to the keg, it's your o-ring. In either case take the post apart and inspect the rubber. Sometimes the rubber is good and a little dab of keg lube will fix the problem.

Firestone & Cornelius parts are not interchangeable. Dismantle, clean, inspect & replace the poppet if needed.

You may need to replace the poppet valve or the o-ring...or the post may just not be tightened down enough (which is what happened to me at first). If you can unscrew the post by hand chances are you need to tighten it. If it is on there tight, you'll need to replace the suspect parts.