The foot bath I was talking about is pure and simple, not heated, H2O2 water foot bath. I use the same water for a few days, 4 days up to a week. When I don't use it, I cover my container so that the water is not exposed to light and does not evaporate too fast. What I should do is transfer the water to some kind of bottle and store it until the next use. But I am too lazy!
I don't know if this water with ES could stay that long. I never tried.
You may dilute it with water so the concentration becomes 2%, 1.5% or 1%. I don't believe it has to be plain 3%. h2o2 is powerful stuff. I would used distilled water to dilute it as tap water containing fluoride and/or chloride will most certainly react with h2o2, hence reducing its efficiency.
For more ideas on how to use h2o2, here's a link, just for you :)