This is the system diagram from TEPCO on June 28 press conference. It appears that the contaminated water is fed from the subdrain outside the Reactor 2 turbine building and from the Reactor 3 turbine building. Nothing from the Reactor 1. The treated water is combined with fresh water before it gets fed to the reactors. Water flow is being adjusted by the numerous valves (lower right of the diagram):
On a separate PDF file, there is an even more convoluted diagram of the contaminated water treatment system by Toshiba-Kurion-AREVA-Hitachi. By switching the valve, they can process the water in AREVA's system first, and then in Kurion's. Considering the frequent downtime of Kurion's system (vessels need to be changed often and flushed often), maybe that's a good idea.
This how it is all laid out physically, including PVC pipes connected to 4 kilometers long.
There are two more diagrams of the system. You can view all 4 diagrams in this file here.
Not so good news is hidden in one of the diagrams (page 3 of the above file) that says "Flow Rate of Treated Water Injected to Reactors: 13 cubic meters/hour".
The current total amount of water being fed to the reactors is 16 cubic meters/hour. They are using fresh (filtered) water in the amount of 3 cubic meters/hour.
So, at least for now, they are still ADDING the contaminated water by 72 cubic meters, or 72 tonnes, per day.
Well, that's infinitely better than adding 400 to 500 tonnes of it every day, like they have been doing for the past 3 months or so.