You can do a "continuous" dilution where you add water and drain it simultaneously (presumably allowing for mixing, so you could add water at one end and drain it from the other), but as was pointed out, this is slower. Specifically, to dilute by 50%, you would need to replace about 69% of your pool water. To dilute by 70%, you would need to replace about 1.2 times (120%) of the volume of your pool. To dilute by 90%, you would need to replace about 2.3 times (230%) of the volume of your pool.

Richard