Product review (5 stars): Our piano tuner uses this.
That is a strong vote of approval. We have recently added humidifier to our ancient upright grand. We are cruel to this instrument - living in a brutal climate, burning wood in the steamy kitchen which is on the other side of the piano wall. The humidifier has made a huge difference in holding its tuning. Since we refill often, tuner felt it wise to treat the water to prevent bacterial/ fungal/mold growth, all frequent issues in our "neck of the woods." No complaints, love that Amazon has it. Even if we could get the sled dogs to town in winter (just kidding, we have great roads), you can't buy it there. I looked. Thanks, Amazon.