You may use three tablespoons of unscented household bleach or Sani-System reverse osmosis system sanitizer (preferred) proven to kill 99.99% of harmful bacteria.

Sanitization Steps:

1. Turn off the cold water supply line to the RO
2. If your system is connected to the refrigerator or ice maker, turn off the line.
3. Turn on the RO faucet and let all the pressure off the system. On a new install this is not necessary.
4. Once the system is empty, turn the RO faucet back off.
5. All filters are to be removed including the membrane. On a new system take out the filters from the housing, placing in a clean place.
6. Take off the pre-filter housing that is typically the filter closest to the feed line. Reconnect all the housings (empty).
7. Pour the entire packet of Sani-System Sanitizer into the pre-filter housing. Or use three tablespoons of unscented household bleach. (5.5%) solution. Screw the housing back onto the manifold. Everything should be connected including the RO faucet.
8. Turn on the cold water supply filling the entire system. This will fill within 5 to 10 minutes since there are no filters in the system. The RO tank will also be full. 
9. Turn on the RO faucet until water flows out and then turn off.
10. If using the Sani-System Sanitizer, let the system set for 60 sec, If using bleach you must let the system set for 30 minutes.
11. Turn off the cold water supply line to the RO and drain the entire system. Repeat this step twice. Refill the system completely and drain again. You should not smell anything coming out of the RO faucet if you do repeat.
12. With the incoming water off, and the system empty, install all of the filters
13. Turn on the incoming water line and check for leaks, allow the system to to fill completely. Inform the customer
14. Note: the first two tanks of RO water should be discarded. There is always residue from the carbon filters that will need to be flushed out.