While getting a RO purifier you might have come across TDS regulator. Some have while some do not. What its all about? Do you need a water purifier with TDS regulator? 

Let me answer these all.

TDS

First of all, TDS is total dissolved solids in water be it mineral, salts, metals etc. In small quantities its ok but if not, it should be taken care of. These RO based water purifier does the same job of bringing TDS levels to acceptable range.

Theres this beautiful guide by Eureka Forbes to understand RO technology & recommendation for purifier range as per TDS levels. They even suggest on if its not required at all.

TDS Regulator- What it does

As the name suggests, it regulates TDS. But now you will think upon, RO is already doing job of regulating TDS. No, here you are wrong. RO just removes TDS from water and brings it to approx 10% of actual levels, it does not regulate it.

So whats the big deal. Yes theres a big deal here. Having very low TDS in water, results in bitter taste. TDS close to 100 is good in taste, higher is not preferable, while lower will be bitter in taste. Bitterness increases as we go further below. Some articles suggest that water in range of 100-500 TDS is acceptable to drink.

So, if your tap water is having water with TDS below 1000, then RO will bring it down by 10% to 100 & below. Here lies the overall problem. Say for eg if its 400, then purified water will have 40. 

To control this, theres TDS Regulator (shown in red circle) in some of water purifier models. Whats it does is to bypaas some of prefiltered water (flow shown in red) before RO stage and mix it with RO processed water later on. This way, hardness level in final stage can be controlled as per users taste. Increase mix up by operating regulator till water tastes good.

TDS Regulator- Operation

This is brand specific & generally done by technician. But if theres genius in you, its an easy task. Here i will cover TDS regulator operation in Eureka Forbes Aquasure RO+UV+MTDS model. But you can find detail for yours in your purifiers manual. Just follow the instructions.

1. Access the back zone of eureka aquasure 
2. Remove the cap covering regulator
3. Loosen the outer ring around slotted screw
4. Use a screw driver to loosen the slotted screw. Dont loosen or tighten it too much. Mark initial position and remember the turns you give
5. Initially regulator is fully closed ie no mixing. Just give it a half anti clockwise turn to increase hardness & check water hardness level. You have to try out before you get desired hardness level or taste.

You can use TDS measuring device to check TDS level in purified water  & bring it in range 80-100, or if you cant find one, just do it slowly and taste water after every half turn, till you get desired taste.

TDS Regulator- Is it required?

Yes you should get a model with regulator if hardness of tap water is way below 1000. Or to be future proof, just get it. Its an important addon, else you will regret it later on. Who knows if you may need it in future.