When an rodi system kicks on the tds is very high for first few min up to even more then 10 min till it gets flushed out and then starts to produce the 0 tds water that is needed. This is why a lot of people has auto flush systems integrated with RO DI, so that it automatically flushes for a couple minutes every time it turns on first that water goes down the drain and then when it’s done flushing, they start collecting the good water. so now what you are doing every time your sump is low your system kicks on and it is literally filling your swamp with super high TDS water never even gets a chance to flush it out and give you the good water supposed to be using. This is why you need to let it run into it say a 5 gallon bucket, and then go from there into your sump