Can I use one 9 volt battery to power multiple pedals?

It'll work.

Obviously, the draw on the battery will be a lot worse than on a single pedal and when you're running a digital pedal that requires 250+ mAh, fun will be over quickly.

 

.... google says, the CS3 has a current draw of 10mAh, which is next to nothing.

 

Well, your average Varta 9V cell has around 550mAh.
So when you activate tuner and comp, you should get more than 6 hours.
And people usually use the Tuner only for a quick tune up, so you should get a gig and a few practices out of one cell.

 

While the spirit of your answer is correct, technically a 9V battery isn't a cell. It's six cells in series. Just sayin.

 

When you bypass a pedal the audio may bypass the circuit but it doesnt cut power to the pedal so it will be drawing power whether you are using it or not.

 

That's why it's called a battery.
Thank you for the correction, I was not sure whether or not a 9V was a battery or a cell.

 

Yes, but especially a Tuner should draw very little while connected.

 

Exactly. The single cells that ppl often call batteries are not actually batteries.

 

Draw on/off differs greatly from pedal to pedal. I actually keep a spreadsheet of ones I've had or have for power source reasons:

 

I power an entire board - TC Polytune > Empress compressor > Fairfield BS > Broughton H/LPF with a single 9v. Tuner is negligible since it’s only used a few seconds at a time and then goes into standby. With 9v rechargeable at 800mAh i get more then 15 hrs runtime.