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Water Specialist

TDS Reading Is Higher Than Normal

If the Pure water TDS is higher than normal after 1-2 full tank flushes, please review the possible reasons below.

  • Membrane was not inserted > Put membrane into housing.
  • Membrane is inserted incorrectly > Re-insert membrane correctly. Refer to Manual.
  • Tap water source water has very high TDS and/or contains certain heavy dissolved elements resulting in TDS higher than usual.
  • Drain water flow restricted or clogged > Check and re-align the drain saddle and drain line.
  • Your input water’s TDS fluctuates resulting in high composite TDS in the holding tank > To verify this, test the filtered water’s TDS before it enters the tank. Please perform the following tests:

    • Test #1 TDS from tank: Dispense some water from the RO faucet, this water comes directly from the tank. Perform a TDS test and record the reading. Do Test #2.
    • Test #2 TDS bypassing tank: Turn OFF tank valve and open the RO faucet. Let the water trickle freely for about 2-3 minutes and catch some water directly from the faucet and perform a TDS test. The TDS here is the actual real time TDS the RO is producing before water enters the tank. Compare this TDS reading with the tank’s TDS you get in Test #1.
  • If tank TDS is higher than Yellow line TDS, that means your source water’s TDS level fluctuates over time. So from day to day, the TDS highs and lows accumulate in the tank resulting in a high composite tds reading.
  • This is especially true if you are on a private well. The well pump’s fluctuating pressure cycles also cause TDS to go up and down. In this case, the real-time TDS from the Yellow line (prior to the tank) or bypassing the tank is the system’s true performance. If this number is within 10% of your tap TDS, then it is within acceptable normal range, and your RO system is working fine.

If the issue was not addressed, please contact us at:
800-880-4808, or

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