ISteedman;4407660; said:you know how some carpet cleaners attach to the sink, but also suck up the soap through a small hose and mix with the water? I wonder if its possible to make a similar setup, but with water conditioner!
Your referring to a siphon set up, in theory you can accurately dose as needed with this. Maybe look into a garden hose fertilizer sprayer, screw on your bottle of Prime onto the dosing part that has a small 1/4" hose on it, and it'll pull in any additives you want, you would need a resrictor on that pickup hose to dose in the small amounts needed in this set up.
Another way would be to add a small section (3-4") of tubing inline with your gravel vacuum/water hose(Python set-up). ie: 1/2" tubing reduced to 7/16". Add your 1/4" or even smaller 1/8" pickup tube in that reduced section...The main diameter reduction will cause the same 'eductor' action and will siphon in whatever you wanted, or leave nothing on the tube and it'll draw in air with your fresh water, helping with chlorine reduction as well.
For gravel vacuuming it would have to be removed though...
I fill my flower watering can with the waste water and water my plants.