How do I clean my R.O. unit membrane?

"Total Dissolved Solids (TDS) is the term used to describe the inorganic salt and small amounts of organic matter present in solution in water, the principal constituents are usually Calcium, Magnesium, Sodium, potassium cations and carbonate, Hydrogen carbonate, Chloride, Sulfate, and nitrate anions."

Guidelines for drinking-water quality , 2nd ed. Vol. 2. Health criteria and other supporting information. World Health Organization, Geneva, 1996.

The first time I checked my Revers Osmosis (R.O.) unit when I bought it. It was giving a reading of TDS 60, but after using it for 6 months it raises to 240, which is not good, or a sign of a non-clean membrane. Even the unit cleans the membrane each on/off cycle for a few seconds by passing a clean water in revers of the membrane normal flow direction that cleans it but it still gives me a high reading of TDS. Therefore, this is how I make it.

Step 1: I Run the Unit Until It Reaches 65 to 70 Psi.

Step 2: Then I Turn It Off, for a Second Then on Again.

one second is okay

Step 3: The Unit Make Its Membrane Wash.

The unit make its membrane wash for few seconds but this time it makes it with pressure this pressure pushes the dirt's out of the membrane.

Step 4: Repeat.

I repeated this for two times and my clean water TDS comes down to 106.

Step 5: Improtant Note

Note: the recommended TDS for drinking water is 120 to 140 (Actually, less than 300mg/liter is good), to achieve that there is a small needle valve on the back of the membrane inlet bypasses a small amount of the water from before the membrane, adjust it to reach the amount of needed TDS. Drinking a low TDS water for a long time may lead to lose the body minerals.