TDS value is 310 ppm in Chennai, Tamil Nadu - Please let me know if this is good for health

I am a resident of Chennai. I get my water supply through metro water (Chennai corporation) and TDS level is about 310-350 PPM.

We have installed a TFT membrane aqua guard Reviva RO system, which has reduced the TDS to 20 TDS.

I have two children, in this case Please suggest this TDS level is good for health if not please let me know what is the level is good for health.

 Thanks.

 Regards

 Velu

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