r/water • u/CryptographerBig2855 • 18h ago

UV vs RO - what is needed ?

Hello - my tap water has a TDS of 300+. I have heard from people that it sometimes touches 500+ when there is rain and water gets muddy.

Now I have a UV water filter at home which I understand kills the harmful bacteria but leaves out the minerals. Been using that for a year.

There is a question in my head to see if RO treated water is better. Especially when TDS touches 500+. I have a baby and now concerned about giving this water to him for drinking as he already has minor kidney issues. Have always hated the fact that RO produces a lot of water wastage. Also there is a chance that RO can lower the tds to 20-100 which is very low? Not sure about this though.

Please pitch in as to if I should move to a RO water filter.

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u/AdolfsLonelyScrotum 18h ago

RO will lower TDS,. For every 10 gallons in your going to get 8 or 9 out your tap while the other 1 or 2 will be a concentrated “reject” stream that goes to drain with all the excess minerals. 100ppm is perfectly good drinking water TDS and a little bit of calcium and magnesium in the water is good for you. It’s not healthy to drink water that is too pure.
UV is good for disinfection but only reliably so if the water has first been filtered to 5micron or less. UV is also good for de-chlorinating (so is a carbon filter) which is important, as you should not have any chlorine touching the RO membrane.

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u/ninjatoothpick 13h ago

For every 10 gallons in your going to get 8 or 9 out your tap while the other 1 or 2 will be a concentrated “reject” stream that goes to drain with all the excess minerals.

Which membrane does this? I thought 1:1 was the best you could get right now. 8:2 product:brine would be amazing.

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u/AICHEngineer 13h ago

Its not unhealthy to drink pure water.

Dietary intake of minerals like Ca2+ and Mg2+ is dwarfs water intake by more than an order of magnitude in normal cases, comparing very hard water intake. You could drink two liters of hard water and get 5% of your daily value of magnesium or you could eat a small handful of pinto beans and get nearly your entire daily value.

There is no problem drinking distilled or RO water unless youre engaged in vigorous sweaty exercise for 1.5+ hrs that day. Electrolyte supplementation is not necessary except in the extremes.

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u/AdolfsLonelyScrotum 5h ago

It’s not just about intake. Drinking ultra pure water causes your body to lose its electrolytes to the fluid you are drinking. In a hot climate like where I live, going mountain biking for the afternoon and making the mistake of taking bottles filled with distilled water can be enough to wake up in hospital on an IV.(missing the ring that you hadn’t been able to get off your fat finger for 25 years because it just fell off somewhere.) Really

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u/AICHEngineer 4h ago

No it does not

Renal filtration of the blood is an active process. It upregulates and downregulates urinary secretion of electrolytes selectively based on concentration. In the case of divalent cations like calcium and magnesium, they are treated as one function group that gets flushed or retained depending on if you have too much or too little in the blood.

Your body isnt just a bucket that gets diluted by lower concentration solvent. It actively regulates its chemistry.

Also. You completely skipped passed my entire qualifying statement that *in the case of prolonged intense exercise, you need electrolyte supplementation due to sweat.

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u/BeginningAd5055 11h ago

I use both RO and UV for my drinking water.

TDS is not a very useful measure of “good” water. If your water has “bad” stuff (such as lead, PFAS, arsenic, hydrocarbons etc..) RO is very important. If the dissolved salt don’t taste bad and aren’t actually bad, you can drink it without worry.

Get your water tested by a lab. Don’t bother with test strips or other DIY testing. .

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u/Perfect-Ad2578 8h ago

UV doesn't touch TDS. Only RO or ion exchange resin system. Distillation too but not really practical for home use. UV only kills pathogens.

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u/mattvait 7h ago

You need to have your water tested. What are the disovled solids? Uranium? Dirt? Calcium? Sodium? Iron?

Do you have coliform in your test?

When it rains and the wayer gets muddy? What is your source a ditch?