Scott.h
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That must be well water I'd assume? That seems high. Fish aside I think the legal city water TDS is around 500, but all around me are WAY less. I'm not sure I'd want to drink that without some sort of purifier
TDS readings
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There is no maximum contaminant level for TDS. Since it is not a measurement of anything specific it is considered asthetic and not a health risk. Many places including Phoenix far exceed 500 or even 1000. Mine varies between 550 and 850 normally but can be higher. It is treated surface water, not well water so you know where all the minerals from the Grand Canyon are now!
Scott.h
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I Checked 3 different sources.. 500 TDS is supposed to be the city water limit
http://www.water-research.net/index.php/water-treatment/tools/total-dissolved-solids
http://www.water-research.net/index.php/water-treatment/tools/total-dissolved-solids
Randy Holmes-Farley
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Plenty of places have TDS above 500 ppm. The 500 is a secondary standard, which means it is a recommendation by the EPA (based largely on taste), but some places simply have no choice but to be above it.
Here is the official discussion by the EPA:
https://www.epa.gov/dwstandardsregu...g-water-standards-guidance-nuisance-chemicals
Scott.h
Valuable Member
So if you lived in a place that had a TDS higher than 500 what would be your options for home filtration? Most drinking water filters are carbon, which doesn't remove TDS. Is there a way to purify water without knowing full RO?
TDS isn't necessarily bad, it's the minerals that give the water it's refreshing taste. That's why mineral or spring water tastes so good. You may or may not need to remove the TDS depending on what it is made up of. You need the total water quality or chemistry report to know for sure.
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captainsmitty
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So back to my original point. Will a second stage of DI on a dual membrane Ro unit help to lower these further down?
Scott.h
Valuable Member
If your TDS reading is 45 pre RO system you shouldn't Need a DI unit at all. I'd think one of your readings isn't correct.
If I misread, and that 45 reading is post RO, change the membrane. If the membrane is new and you are still 14 pre DI, your original TDS must be sky high, or not truly 45. OR it's a point of sale membrane.
You might get a new TDS meter and recheck everything because if your pre RO system is truly 45 that's exceptional incoming water. And your post RO reading should be zero or 1. Without it even going through DI.
If I misread, and that 45 reading is post RO, change the membrane. If the membrane is new and you are still 14 pre DI, your original TDS must be sky high, or not truly 45. OR it's a point of sale membrane.
You might get a new TDS meter and recheck everything because if your pre RO system is truly 45 that's exceptional incoming water. And your post RO reading should be zero or 1. Without it even going through DI.
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Dual membranes normally have a little higher RO only TDS since you are sending the concentrated brine from the first into the second membrane, and contrary to what some will try and tell you, they are NOT water savers.
Adding a second DI is just a crutch propping up a bad RO membrane and does not fix the problem.
Using a handheld TDS meter, what is your tap water TDS, your RO only TDS and your RO/DI TDS?
Adding a second DI is just a crutch propping up a bad RO membrane and does not fix the problem.
Using a handheld TDS meter, what is your tap water TDS, your RO only TDS and your RO/DI TDS?
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captainsmitty
Active Member
Ill have to check the incoming water with a separate meter. Ill try taking a sample to my fish store (Neptune Aquatics in San Jose ca)
Buy yourself a good ATC handheld TDS meter, your RO/DI will thank you. I haven't turned either of my dual inlines on in a couple years.
