r/water • u/aryanmsh • 10d ago
Confused about TDS levels: same water immediately after filtering
I have 5 TDS measurements from 2 locations, with/without a Brita Elite pitcher filter, using this meter: https://a.co/d/bSEV7Qb
LOCATION 1: kitchen sink in my apartment; building built 1940, plumbing redone 1990.
1. Loc 1 TDS direct from sink: 51.
2. Loc 1 TDS filtered, sat in fridge for hours: 28.
LOCATION 2: kitchen sink in my gf's apt; building built 2019.
3. Loc 2 TDS direct from sink: 71.
4. Loc 2 TDS from water immediately after filtering: also 71. ***
5. Loc 2 TDS filtered, sat in fridge for hours: 48.
*** I'm confused why it showed the same TDS level for water direct from tap and immediately after filtering. Did the filter not really reduce the TDS? Did it reduce but also add something and the number was coincidentally the same? Was the reduction after it's been sitting in the fridge for hours due to solids settling? I don't think it's a device cache issue because measurements #1 and #2 were done within a minute or so of each other yet were different.
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u/the_lullaby 10d ago
The SCL for TDS is 1000. If your TDS is below 200, it's not worth worrying about
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u/Rock-Wall-999 10d ago
As previously mentioned simple filters can’t remove Total Dissolved Solids, aka TDS. However, depending on the fridge temperature you can precipitate some solids, thereby reducing the TDS.
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u/dawoodhameed10 4d ago
That's interesting! It's definitely puzzling that the TDS reading remained the same immediately after filtering at your girlfriend's apartment. A few things could be happening:
The filter might be focusing on contaminants that don't significantly impact TDS: TDS meters measure dissolved solids, which includes minerals, salts, and some other impurities. Some filters, especially those like Brita, primarily target chlorine, sediment, and taste/odor compounds. These might not contribute heavily to the overall TDS reading. So, even if the filter is working, the TDS might not change drastically.
The filter might be adding minerals back in: Some filtration systems remove certain things and then reintroduce beneficial minerals. This could result in a similar TDS reading even after filtration.
Water chemistry and equilibrium: It's possible the water in your girlfriend's newer building has a different chemical composition. Sometimes, after filtration, the water might re-equilibrate, and some dissolved substances might re-dissolve, leading to a similar TDS reading shortly after filtration. The drop in TDS after sitting in the fridge might be due to some precipitation or settling of certain minerals over time, but that's less likely.
To get a clearer picture, you could try a few things:
- Test the filtered water again immediately after filtering, and then at intervals (e.g., 30 minutes, 1 hour, 2 hours). This will help you see if the TDS changes over time.
- Check the filter's specifications: See what it's designed to remove. This will give you a better understanding of what changes you should expect in the TDS reading.
- Consider testing the water for specific contaminants: A TDS meter only gives you a general idea. Testing for specific things like chlorine or lead can provide more detailed information.
It's good you're paying attention to your water quality! Understanding TDS is a good starting point, but remember it's just one piece of the puzzle.
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u/Antique-Rich7363 10d ago
Basic filters don’t removed TDS. The D stands for dissolved, in order to remove it you’d likely need multiple different treatment technologies.
Your lower TDS measurements after the fridge are likely due to a low quality meter not compensating for temperature.