TDS meter findings!!

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MarkW19

Aquarium Advice Addict
Joined
Mar 25, 2004
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I just bought a TDS meter, and am shocked at the results!

I've found out my RO unit isn't working, at all. Water straight out of my tap has the same reading (about 150ppm) as water I've been storing in a bottle from my RO unit for about a month.

Obviously something's amiss...what should I be checking for? It's one of the Kent 24gal/day full size units.
 
Depending on how long you have the ro unit, and I don't mean to state the obvious, but either the membrane itself is shot or is is defective. Also, if you never changed the carbon prefilter and that went bad, the chlorine in tap water will destroy a ro membrane. Just curious, but why do you have ro water stored for a month?
 
I've since spoken to fishfreek about this (thanks!) :p

I store it for emergency waterchanges etc. :)

The clean cup thing worked - these TDS meters are so sensitive! Even the slightest bit of dust in the water throws the reading out by like a hundred! All seems ok now though...
 
OK, I'm now getting a reading of 22ppm straight from my RO unit, as opposed to 150ppm from my tap.

I was really hoping for 10 or less - is 22 ok?
 
I've just tested 15 gallons of water that I've just done with my RO unit, and it's come out at 2ppm! I did 3 tests and they all came out the same. Two in different cups, and one straight in my water container tank. Very pleased. I then put the water in some plastic containers and carried it downstairs, before putting it back in the tank. I then got a reading of 4ppm - perhaps the containers added the extra bit, or it might've been a bit of dust or whatever.

At any rate, 4ppm is fantastic from a normal RO (not DI) unit! :)

One strange thing though, I RO'd a little bit of water into a cup yesterday to test the ppm, and it came out at 22ppm?
 
Yeah, it's quite common for a lot of these TDS meters to have an accuracy of +/- 2%.. so if your particular device has a range of 0-999 then that would account for the fluctuation of 20ppm.. I think that's how it works anyway, Maths was never my strength :lol:
 
My TDS meter actually goes up to 9,999 :p

Surely it won't be so inaccurate though?
 
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