how can I nevert to yosemite from el capitan if i don't have a time machine?

I have a MacBook Pro mid 2009 and upgraded to El Capitan a while ago and since then my laptop has been painfully slow. Everything runs slow from starting the laptop to logging off and everything in between. also my time machine is now currently working.

Is it possible to downgrade back to yosemite without the time machine and just go back to how it was before?

Thanks

Sao