# TDS readings



## Aqua sobriquet (6 Apr 2019)

I hope this is in the right place. I took a reading straight from the kitchen tap and got 265ppm. I then took a reading from the drinking water part of the tap that goes through an in-line Brita filter and got 185ppm. Any ideas on what the filter is actually removing. It’s not much but certainly something?
The meter is a H&M aquaPro.


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## Konsa (6 Apr 2019)

Hi
The TDS is every ion present in the water.The actual reading is irrelevant as I dont know what exactly is in it .Actual reading matters only if U are adding minerals to RO water for examle in shrimp keeping.
Regards Konsa


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## dw1305 (6 Apr 2019)

Hi all,





Aqua sobriquet said:


> Any ideas on what the filter is actually removing. It’s not much but certainly something?


I've never used a Brita filter, but it looks like it has an ion exchange resin. Judging from the  <"Brita FAQ"> think it is pre-loaded with potassium (K), so it will exchange a Ca++ ion for two K+ ions. If you have hard water it will pretty soon be exhausted.

Because it has reduced conductivity it must have sequestered an ion as well, this could either be a cation or an anion. This would be via a DI resin which will swap a hydrogen (H+) ion for cation (like Na+ or Ca++), or a hydroxyl (OH-) ion for an anion (Cl-, SO4-- etc). Add together a H+ and a OH-, you have H2O and you've reduced conductivity.

Sounds like it is probably a <"mixed bed resin">.

cheers Darrel


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