You will need two. One for forcing carbonation and soda @ 25 psi and one for servicing pressure ( 5 psi) for the ales. You can have two regulators on one CO2 bottle, so there's a small savings.
The alternative is to have one regulator, one manifold and set the pressure for forcing and soda. That is what I do. I keep the ale keg valves shut off and burp them just enough to keep the ale flowing.
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