The pump station will only supply water at a rate equal to the slowest pump connected. For instance I have been experimenting a lot with this, Ok you have 6 wells, 5 of which can supply 6 L/hr each, one pump has two sabatiers on it so it can only supply 2 L/hr. The output of the pump (with one extension of course) is connected to a vertical tank or a large tank. You would think logically if 5 wells supplies 6 L/hr and one supplies 2 L/hr then you should be able to fill an external tank at 32 L/hr. What actually happens is if you try to push more than 2 L/hr into the external tank the well resevoirs start to drain and the external tank will never fill because the base it's connected to will eat every last drop as you can push into it. Also I believe if your base is using let's say 12 L/hr and somehow you were able to feed the external tank at 10000 L/hr it will still stay empty. I have even tried to feed each building with it's own water well to see if it helps but the map shows all buildings with no water but strangely enough the plants don't wilt. I think the problem is the base won't slow the water flowing into it to allow the tanks to fill and the pumps need to be able to combine the input with the output so you can achieve the maximum flow from all inputs on the output.
Hope this helps.
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