Effective. The process to refill water chamber which must be done at least once each oral treatment cycle and is clumsy. It is clumsy as it requires detachment and reattachment of the chamber to body of device which is not a smooth operation. I would suggest a port on side of water chamber to allow water to flow into chamber either from faucet or a small pour cup. The chamber could still be removable to facilitate cleaning. Aside from this detraction the unit provides good portable function and is operationally servicable. It works.