Why Does TDS Rise in the First CL of Water Produced?

Natural osmosis

To answer this question, we need to discuss the principle of osmosis. Osmosis is a diffusion phenomenon observed when solvent molecules pass through a semipermeable membrane separating two solutions with different solute concentrations; the net transfer of solvent then occurs from the less concentrated solution to the more concentrated solution.

By applying osmotic pressure on the more concentrated side, reverse osmosis makes it possible to reverse this phenomenon, creating a large difference in concentration between the two solutions. However, when the booster pump is not powered, the pressure equalizes on each side of the membrane, and as a result the concentration also equalizes through natural osmosis.

When you then start your RO system, this small amount of water is sent to the faucet/tank first, which explains this temporary rise in TDS.

Not all particles take part in this phenomenon, only the smallest minerals (calcium, magnesium), so although the water is more concentrated, it still remains good quality. If you absolutely want to avoid mineral water, you can let the water run for a few seconds before filling your glass, but this is not necessary.

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REVERSE OSMOSIS

Why Does TDS Rise in the First CL of Water Produced?

Natural osmosis

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