TDS Help

[Acro Freak]

Hi foks, I'm looking for some help with a TDS meter I just purchased, It's a Hanna Dist1 Model HI-98301 reads from 0-1999 ppm. I just tested my tap water and got a reading of 176ppm, then tried water from 10G. jugs from water cooler and got a reading of 270ppm, then tried on bottled water from Aberfoyle & got a reading of 510ppm. Am I missing something in here or these numbers has to be divided to get proper tds reading, lookes to me that tap water has less tds than bottled water...Any help is appriciated.

:confused:

[Mako]

Is the bottled water spring water? If so, then yes there is a very good chance it is higher in TDS than your tap. Try using the meter on some distilled water and see what you get.

[mirski57]

My household tap water runs in the 230 range. Then when I test it against my RO/Di its 0.

[MJB]

John from Aquatic Reef Systems turned me on to this.Go buy a bottle of Aquafina Pepsi's bottled water. He said TDS is always around 10-12. Worked for me when I wanted to know if my TDS meter was working properly in a pinch. I'm curious to know if someone else can verify this.--MJB

[SAT]

There's a common misconception that TDS is a measure of "goodness". Actually it just measures conductivity of the water, which can be caused any number of different ions, good or bad. Bottled mineral water should have a high reading because the minerals improve the taste and are often good for you.

The purpose of a TDS meter is to to tell if your RO system is working properly. Take a reading of your tap water. Take a reading of your purified water. If it's an RO system, the reading should be less than 10% of the tap water. If it's RO/DI, the reading should be zero or close to it.

[SAT]

Acro Freak,

And, by the way,

[welcome]

[Acro Freak]

Am I missing something here or my RO unit is not working properly, my tap water reads about 176ppm, then If I disconnect my Membrance run it only with Sidment & Carbon filters I get 160ppm but when I hook up the Membrance to be a full RO unit I get reading of 1230ppm, don't get it something is not right ...:eek1:

[Acro Freak]

Thanks for the warm welcome...:D

[SAT]

Yeah, that's not right. There are two outputs from the RO unit. One is for purified water and the other is supposed to go down the drain. One possibility is you're reading the waste water. You can usually tell because you get about 4X as much waste water as purified water.

Another possibility is there's some residual contamination and you just need to run it a while to flush it out.

If you leave the unit idle for a while, the first batch of water out of it will have higher than normal TDS (but not normally higher than tap water). You should always allow it to flush a pint or so before taking a reading.

[Summitpa]

I'm curious if you should get a higher reading reading the wastewater from an RO myself. In my case, I get 62ppm into the RO, 0ppm on the good output, 62 ppm on the waste water. Logically I agree that you should get a higher reading on the waste side, but , this is water that didn't pass through the membrane just sediment and carbon filters. It just sailed through the unit.

BTW, I have a hanna TDS also. Sounds like you might have a bad one there. I'd try changing the batteries then try reading again. Electronic circuits do some really strange things when wrong voltage is present(batteries going dead). After changing batteries try MJB's idea.

[SAT]

Originally posted by Summitpa
I'm curious if you should get a higher reading reading the wastewater from an RO myself. In my case, I get 62ppm into the RO, 0ppm on the good output, 62 ppm on the waste water. Logically I agree that you should get a higher reading on the waste side, but , this is water that didn't pass through the membrane just sediment and carbon filters. It just sailed through the unit.
Anything that doesn't go through the RO membrane has to still be in the unit (sediment or carbon filter) or in the waste. I would expect the waste to be a bit higher than the tap water. However, if the amount trapped in the carbon filter was about the same as the amount added by the RO membrane, I could imagine getting the same reading.

I agree, by the way, that a 7X difference is not explained by getting the output mixed up.

[Acro Freak]

I'm 100% sure I have the right output as the good side water only drips while the waste side is constant high flow, this morning I've even hooked up a second carbon cartridge so now it goes thru a sidment filter & then thru dual carbon units before gets to the membrance still with no luck.
The output just before the membrance is 158ppm passing thru sidment & dual carbon but when it pases thru the membrance it hits 1280ppm, even if I measure the waste side of the RO I think I should still get better results than just with sidment & carbon since it's already pasing thru the membrance and should be filtered further by the TFC unit... Correct me if I'm wrong please.

[SAT]

No, you're right. The extra dissolved solids must be coming from inside the RO housing. Is this a brand new RO unit? It could just be some residual from the manufacturing process. Try letting it run for a little while and see if the problem goes away. If it doesn't, you should have a discussion with the vendor.

[Summitpa]

Good point SAT. When I got mine, instructions said the unit is assembled with vegitable based lubricant (i forget why) and you needed to make about 60 gallons to clear out or "season" the filters so to speak.

Acro, if you have a LFS that makes RO water take the meter to them and ask for a sample of their water. This should prove or disprove the meter. It should be 0 or darn close to it.

[Acro Freak]

Ok guys I went out & bought a bottle of Aquafina water & tested it with my TDS meter got a reading of 13ppm which is almost close to manufacturer specs. then on my way home stoped by my lfs & test on a sample of his R/O water got a reading of 1ppm only...Wow was I was shocked so now I know that my TDS meter is working right I came home & let the R/O unit run for about 10 min. took a sample & 4ppm now that I feel better that my R/O unit is working there is one more problem, it's making very little good water & wasting alomst 50X it's a Filmtec 100GPD membrance & I know that the manufacturer run's their test based on 77F but my cold water is only 60F, could this be a reason why I'm getting so little make-up water & is there anything I can do about it to improve the quantity....
Ps: Thanks for all of you who helped & guided me to resolve my difficulties.

[Acro Freak]

Sorry, forgot to mention that my water presure is 60PSI.:D

[MJB]

Cold water will decrease production but you're not that bad. PSI is OK. The waste to good water should be ~4/1. It might look like your're wasting more than you are. Get a couple gallon jugs or something and see what you're getting over a fixed period of time You can also get an inline needle valve for the waste side that will allow you to adjust that waste ratio down a bit. In the end you won't save a whole lot of water and may shorten the effective life of the membrane. Sounds to me like you're in business. These things waste a lot of H2O.HTH--MJB

P.S.-Wierd about the Aquafina huh?

[Summitpa]

I have a 100gpd unit also. My temp is probably around the same as yours also. PSI is about 70. I'll make 5 gallons tomorrow morning and time it for you. My best guess off the top of my flat head is I make about 2.5g an hour