[jo5hm4n]

Just a random comment for a sunday afternoon.

Checked my tds before that goes through my 450GPD RO then through a 6.5L Vessel, then into storage tank.  Water was reading at 000ppm, which is great!

But i don't quite understand why, because the last 8 weeks or so it's been reading at 002ppm.  And i have been using at least 1k Litres per week, so after doing like best part of 10k Litres, the ppm has dropped?

Can anybody care to explain that for me.  I am just interested, because last time i checked the PPM rises over time + the more you use it LOL.

Maybe i found a loophole?

*Sidenote - Resin was changed in August, along with the RO being brand new.  Was reading 000PPM for around 2-4 weeks, before then going up to 2ppm, then now it's dropped again.

[Tom White]

I reckon it's something to do with the colder temperature:



http://www.reagecon.com/pdf/technicalpapers/Effect_of_Temperature_TSP-07_Issue3.pdf

[Spruce]

Hi Tosh

It could also be a faulty tds meter.

It could also be that as the water temperature drops your r/o becomes more efficient with the denser water producing a higher quality pure with lower tds. Your r/o will also not be processing water as quickly as it does when the water is warmer.

It could also be that the source water is from a different supply. Our tap water fluctuates between 99 and 125. I checked the output from the r/o on Friday and it was reading 1ppm and occasionally flicking to 2ppm. I meant to take a tds reading from the inside tap but forgot. That membrane is 4 years old and that's the best I've seen it perform for a long time. It usually sticks at 2ppm.

And of course, there is the point the article makes about the conductivity of water at different temperatures. I once tested the ppm of cold water in a stainless steel pot on the stove being slowly warmed up. As the water temperature increased the tds reading of the same water did rise, but it wasn't by much at all.

.

[Arnold Palmer]

I reckon it's something to do with the colder temperature:



http://www.reagecon.com/pdf/technicalpapers/Effect_of_Temperature_TSP-07_Issue3.pdf

Yeah at 2% per degree Celsius described as a "reasonable approximation" it would need a fair old temperature differential to take it from 2ppm to 0ppm.