Chris Jury

Experienced Reefer
Location
Kaneohe, HI
Rating - 0%
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Guys, just for sake of clarity, the TDS tells you nothing about how clean, dirty, or whatever the water is, it just tells you whether there are dissolved ions in the water or now. A TDS of 1000 is harmless if it's table salt (NaCl) giving the reading, whereas a TDS of 1-2 could well be quite deadly it's cyanide (CN-) giving you that reading.

In general, we assume that there are nasty things in tap water we don't want in our tanks (usually true). If we remove most of those nasty things so that we get a TDS less than 1, we can be reasonably confident our water is ok to use without problems. However, if there is nothing particularly troublesome in the water, the TDS is irrelevant, whereas if there is some very noxious compound, even a TDS of 1 may not be good enough.

Years ago I had a tank at my parent's house. Their tap water is from a well, out in the country in MI. The TDS was well over 400 due to dissolved limestone (CaCO3) in the water. Several times when I was out of RO I used just tap water to top off that tank, keeping my fingers crossed. The tank thrived. In fact, I eventually realized that there were no negatives from using this water (it seemd to be very clean, had undetectable nutrients, etc.) and ended up using straight tap water for that tank for a couple of years with very good results. If I were doing this in most municipalities, the tank would have been a disgusting mess of algae and death if only for the very high phoshate levels.

Anyway, just to reiterate, the TDS tells you nothing about how clean or dirty water is, it just tells you how much charged 'stuff' is in the water. Pure sea water at a salinity of 35 ppt will give you a TDS of about 35,000 because it has a heck of a lot of dissolved ions.

cj
 

Ariel110G

Advanced Reefer
Location
Lakewood NJ
Rating - 100%
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Just tested NYC water coming out of our pipes (Bklyn to be specific) with a Digital TDS Meter and the reading I got was 21 PPM
After I Purified it I got a clean reading of 1 PPM
Anyone else getting similar , worse or better before and after?




I?m in the same neighborhood I?m getting 21 TDS in and 0 TDS out


By be before the water goes in to the DI it?s already at 0 TDS!!!
 
Last edited:

PhoenixOne

"Drugs are bad...mmmkay!"
Location
Old Bethpage
Rating - 100%
1   0   0
Guys, just for sake of clarity, the TDS tells you nothing about how clean, dirty, or whatever the water is, it just tells you whether there are dissolved ions in the water or now. A TDS of 1000 is harmless if it's table salt (NaCl) giving the reading, whereas a TDS of 1-2 could well be quite deadly it's cyanide (CN-) giving you that reading.

In general, we assume that there are nasty things in tap water we don't want in our tanks (usually true). If we remove most of those nasty things so that we get a TDS less than 1, we can be reasonably confident our water is ok to use without problems. However, if there is nothing particularly troublesome in the water, the TDS is irrelevant, whereas if there is some very noxious compound, even a TDS of 1 may not be good enough.

Years ago I had a tank at my parent's house. Their tap water is from a well, out in the country in MI. The TDS was well over 400 due to dissolved limestone (CaCO3) in the water. Several times when I was out of RO I used just tap water to top off that tank, keeping my fingers crossed. The tank thrived. In fact, I eventually realized that there were no negatives from using this water (it seemd to be very clean, had undetectable nutrients, etc.) and ended up using straight tap water for that tank for a couple of years with very good results. If I were doing this in most municipalities, the tank would have been a disgusting mess of algae and death if only for the very high phoshate levels.

Anyway, just to reiterate, the TDS tells you nothing about how clean or dirty water is, it just tells you how much charged 'stuff' is in the water. Pure sea water at a salinity of 35 ppt will give you a TDS of about 35,000 because it has a heck of a lot of dissolved ions.

cj

Nicely done Chris. :thrash:
 

Ariel110G

Advanced Reefer
Location
Lakewood NJ
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47   0   0
So this is my question, I have a RO/DI unit, with a TDS meter, when I check for TDS it reads 0 even before the water goes into the DI canister, so in my case do I even need to run the water through the DI?? Or the DI removes stuff that the TDS meter dose not detect.
 

PhoenixOne

"Drugs are bad...mmmkay!"
Location
Old Bethpage
Rating - 100%
1   0   0
@Ariel: I'd double check that reading. Maybe you can borrow a handheld/inline meter from someone to double check? It maybe possible to have 0 TDS without DI, but I would double check just to make sure. Just a couple of weeks ago, I found that my TDS meter needed to be recalibrated.
 

Ariel110G

Advanced Reefer
Location
Lakewood NJ
Rating - 100%
47   0   0
Ok cool, just for the record, I have 2 TDS meters one on the 1st sediment canister of my RO unit & the other one is on the DI canister, when the water hits the 1st canister before it goes in it reads 21-22 TDS, so it looks like in Brooklyn NY my neighborhood tap water has 21-22 TDS
 

Geraud

Advanced Reefer
Location
Manhattan
Rating - 100%
49   0   0
My TDS reading are 35-38 in Manhattan.

On a side note, when I lived in IL they had this big banner at the airport "best tasting water in the country".

On some days the water was greenish blue, and smelled of chlorine. I guess the guys who had done the taste test liked a cup of bleach every morning.
 

TonyHNY

Back from a break
Location
Jamaica, NY
Rating - 100%
32   0   0
25ppm in Kew Gardens and 35ppm in Jackson Heights. NYC water IS the best :) I probably just need a sediment filter with a Deionizer to get the ppm to zero (save a LOT of water this way) but I've been using a RO/DI setup...
 

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