0 tds - what does it really mean?

[brians_224]

Thanks for your time.

Does ro/di water with a tds of 0 have any phosphates in it?

[PatMayo]

It should not. A good RO/DI system effectively putting out zero TDS should not have any phosphates in it.

Regards,

Pat

[demonsp]

ro/di water would filter out your phosphates.

[nick18tjetta]

0 TDS should mean nothing but pure H2O.

[drummereef]

Pure water indeed. Although, testing can be the missing link. Zero TDS is misconstrued with zero indicated TDS. Here's a bit from the SpectraPure boys.



What is ZERO TDS? Is it real??
I thought I would comment on the common misnomer "ZERO TDS". Persons stating ZERO TDS I assume are referring to Zero Indicated TDS. What's the difference you ask? Well, quite a bit when you are really talking about ultrapure water. Ultrapure water is about 18.2 mohms or about 0.05 microseimens. Most Reefers are after such ultrapure water in our experience. Thus, if there were such a thing as "ZERO TDS", it might be more appropriately measured around 0.05 micro siemens. Unfortunately, most (not all) inexpensive TDS meters can resolve at best about 5 micro seimens. That is several decades less sensitivity than required to be stating so called "ZERO TDS".

While 5 micro siemens conductivity (at an affordable price and rugged instrument easily operated and maintained) is very reasonable for for break-through detection to signal cartridge replacement required, it is clearly not sufficient to measure or crow about having “ZERO TDS” . Thus, postings where one has "measured" a system or component performance and state they have "ZERO TDS" should be careful to quantify the accuracy of the instrument they are using to make such a claim. Hopefully this will shed some light on... zero is not always zero.

[sanababit]

tds=total dissolved solids in the water, ppm=parts per million, so if you have a value of 0ppm it means that the total dissolved solids that at present in the water is 0, so water is ultra purified, its basicaly pure H2O

[fatdaddy]

Originally posted by brians_224
Does ro/di water with a tds of 0 have any phosphates in it?

Just use a phosphate test to test it. It should be zero (or maybe your test is off), but you'll need to track down the problem.

[Leafer]

Okay, I'll toss in on this... My Hanna DIST5 reads 0 TDS on my RO water (Pinacle+ 100gpd). From this thread I would conclude an add on DI cartridge is unnecessary for me. Am I incorrect?

[papagimp]

If your properly calibrated TDS meter is reading zero, than no, I wouldnot recommend an added DI cartridge. Although it's not going to hurt to add one, and would give a tad buffer to when your other cartridges need replacment. A 0 TDS reading before the water reaches the DI cartridge should make that cartridge last a heck of a long time.

[brians_224]

thanks all

[AZDesertRat]

TDS meters are +/- 2% of full scale so can easily be off by 20 ppm TDS even when new.