I have been doing a bit of research on it lately b/c we need to replace ours. Many I have looked at did not have a high enough GPM, but this sight was pretty helpful. http://www.excelwater.com/eng/b2c/sh...77213a9edad2e3
I thought about refilling the old unit but the price difference was not worth it. Our valve is leaking a bit and you have to replace the tube insade as well.
Other recommendations are always helpful.