How To Deal With Hydrogen Peroxide After De-Yellowing? I was able to remove the annoying yellowing effect from old white and lightgray bricks with the usage of hydrogen peroxide. With great results I have to say. Now I wonder what to do with the remaining fluid. Is there a danger to poison someone when it's used in my household? Is it ok to drain it down the sink? Any advice on how to deal with it is welcome.

Another thing, when do I have to change the fluid? Will the effect gradually decrease?
After doing a simple search, it seems that the general consensus is, it's okay to pour the used amount down the drain.  

Most of us get it.  The stuff's been sitting in your house taking up space, and because of the unfamiliarity with this chemical, you and environmentally conscious thinkers such as yourself, would never want to further harm our shared environment.

Bottom line: No new bubbles means no more potency, the green light to pour away.