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How to Lower TDS

Sep 25, 2012
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Ages ago I asked which was the difference between TDS and PH and I have to thank two of your members for their clear and detailed explanations.

Since then I was advised to buy an HMA filter, which I did. But one of my major problems at the moment is the TDS values for water straight out of the filter is over 550. I am aware that if I use RO water I can lower the TDS, but I was wondering if it is possible to buy different cartridges to do the job.Can you help?

I would like to thank you for your fantastic help.


Aug 8, 2015
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According to GH HMA refers to:
Basically this refers to a resin based water filter used to filter out chlorine, metals and other contaminants in the water without removing minerals and salts. Therefore does not change the GH of the water.
Assuming that statement is correct the filter only removes heavy metals and leaves the rest untouched. Heavy metals in general don't dissolve well in water. Therefore most of your TDS is not from heavy metals. Most of your TDS reading is from things that dissolve easily in water such as potassium, sodium, calcium, magnesium, and gasses. Only a RO filter or deionizing filters will remove things that are easily dissolved in water. However with your TDS reading at 550 a DI filter probably wouldn't last long due to buildup inside the filter. And it would probably need frequent replacement or will need to be regenerated frequently. RO water however constantly purges out this buildup and sends it down the drain. So in hard water conditions like yours an RO membrane can go a year or more before it needs to be replaced.
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