TDS readings?

[MizTanks]

Bought me a little TDS meter. Tested my tap water=157ppm. I've no idea what this means. I'm going to assume this is high~right?

[AZDesertRat]

157 is a little better than average TDS which is around 250 nationwide.
Its certainly not something I would put in my reef tanks but depending on hwta the 157 is made up of its probably fine for drinking. Thats the problem with TDS, its a measurement of everything electrically conductive in the water so does not speciate or identify anything in particular. It could be calcium and magnesium or it could be phosphates, silicates, nitrates, copper, iron or any number of other things.

The beauty of a RO/DI system is it removes everything and is not selective so a reading of 0 TDS means you eliminated it all and are starting with fresh pure water again.

[CableGuy]

157 really isnt too bad...

Where I am it is ~90, but Detroit has some of the cleanest water around.

[mcleodm]

Originally Posted by CableGuy

157 really isnt too bad...

Where I am it is ~90, but Detroit has some of the cleanest water around.

I get about 110 to 120 in wixom. 157 is pretty good because you won't be replacing your filters as often as others

[Heidi]

Wow ours is really bad over here and even the RO filtered water at the grocery store still reads phosphates with my API test. I the TDS here is 180 from the tap, 155 from our britta (just incase anyone wondered). Those fridge filters are so expensive and yet all they take out is 30...hmmm, I love my ROdi!

[AZDesertRat]

Prefilters and carbons blocks have very little to absolutely nothing to do with TDS so get changed every 6 months regardless if you have 50 TDS or 5000 TDS. They are there to protect the RO membrane from suspended solids, big stuff like sdeiment, silt, particulates, sand and colloidal materials in the .5 micron range and larger plus chlorine in the case of the carbon block. The membrane removes the smal stuff, dissolved solids in the 0.0001 micron range.
Hobbyist grade saltwater test kits are not designed to test phosphates or other things in ultrapure water like RO or RO/DI so mean nothing. It takes lab grade instruments to test RO/DI water so your best friend is a good handheld TDS meter. I prefer the HM Digital COM-100 as it is 10x more sensitive and accurate than the normal meters and is stil only around $59.

[marc49127]

My TDS readings out of the tap pegged my meter which is calibrated up to 450! So who knows how high they really are! Needless to say but my filters and di don't last very long!

[nate_newton]

Originally Posted by Heidi

Wow ours is really bad over here and even the RO filtered water at the grocery store still reads phosphates with my API test. I the TDS here is 180 from the tap, 155 from our britta (just incase anyone wondered). Those fridge filters are so expensive and yet all they take out is 30...hmmm, I love my ROdi!

Interesting, ours is around 120 on the basement coldwater washer line.

[AZDesertRat]

Mine in Phoenix is never less than 650 and it can get over 1200 in parts of the Valley.