Valoy-
The 225 is nearly identical to the 235S. I find I need to pull the rings upward to drain the lines. I also open the small valve which is under the heater vent pipe near the pull ring. There are also two pull rings in my bathroom vanity that I need to open to drain the system. I find after opening them and running the water pump for pressure (don't let it run dry) it drains quite quickly.
Don't forget to push the rings down when finished.
Dario, old friend - Is your ring already in the 'up' position hence you can't pull it?
-TT