I think a flush in soil means that for example, if you have your plant in a 3 gallon pot, water it with a total of 6 gallons. And doing it over a sink might be nice because it's sure going to drain a lot out of the holes, which is what you want.

I'm not a soil grower though, so I'm just repeating what I've read a dozen times on here.

I think the point is, that if your runoff is measuring a lot lower than what is optimal (and lower than what you water with), it means your soil contains something that is taking your water PH down more than you want. But again, wait for more experienced soil growers advice and clarification.
MisterE Reviewed by MisterE on . my plant is half dead so i went away for 3 days and i have come back and my month old plants leaves are all droopy. the one around the bottom have died but the 7 pronged leaves at the top are drooping downwards. before i left i watered and fretilized it, any suggestions on how i can save it? it was on 24 hours light but i switched to 12/12 today Rating: 5