Change existing application pool identity of a SharePoint web application

Following is the PowerShell script I used to change current application pool identity to a different managed account.

1. $web = Get-SPWebApplication "http://sp13"
2. $account = Get-SPManagedAccount -Identity "dev\portalapppool"
3. $web.ApplicationPool.ManagedAccount = $account
4. $web.ApplicationPool.Update()
5. $web.ApplicationPool.Deploy()

That’s all I had to do :)

I described how to change application pools for service applications in this article. It has answers to your questions like, “Why can’t I change the application pool identity directly from the IIS itself?”.