TDS Detective Work

[BHenderson79]

I recently got a TDS meter and I was just looking for some answers with regard to some numbers I'm seeing. Please let me know if you think my assumptions are correct!

Last week I replaced the cartridges on my RO unit. I emptied the old water in the collection basin and made a new batch of water. I checked the TDS when it was done and got a reading of 0. All good!

I used that water for a water change, then made a new batch of RO water in the basin. When it was full, I turned off the RO faucet and left it for 3 or 4 days. Today I came to do another water change and used that water. The way I was doing the water change was: scoop a 2-gallon bucket into the RO water basin. Mix a cup of salt into the bucket, siphon the bucket into the tank. Then I'd bring the same bucket back down and repeat.

Out of curiosity, I tested the TDS after I'd already done a couple bucketfuls of water. The TDS in the RO water basin read at 105. By the time I was done the water change, the RO basin water was reading over 400 TDS. So is it safe to assume that the ridiculous TDS jump is just from me contaminating the RO basin water with some salt residue by using the same bucket that I mixed in the salt?

Thanks!

 

[AQTCJAK]

I just re-created exactly what you did.

I first check the TDS from my 180 Gallon Storage tank
TDS 0
Then I checked the TDS of my mixing VAT
TDS 562
I went one step farther checked the TDS in my Display Tank
TDS 562
I thought what if I take water from the mixing VAT wet the inside of a container then dump it out several time & fill it with enough RO/DI to test & the answer was
TDS 562
The TDS meter was rinsed in RO/DI water every time & checked to ensure it read 0 before each test

So you are correct the salt residue is what is raising your TDS

 

[BHenderson79]

Wow, thanks for the effort for recreating that!
I suppose I'll start using 2 different buckets to prevent that. Even though it's just salt, it'll be helpful to keep my TDS readings in the RO basin true so I have a clearer indication of the water quality coming out of the system.

By the way, Jack, Fedex says the skimmer should be showing up today - so i will be setting it up tonight, hopefully!

 

[AQTCJAK]

Glad to be of help

Very Cool

 

[BobBursek]

Uncovered RO/Di water is so ion free it will pick them up out of the air, it does not mean the water is bad any more it just give you a "false" reading on your TDS meter, the water was still pure when you made it but picking up the ions in the air will show TDS's on your meter, cat litter boxes close by are the worst cause of it.

 

[BHenderson79]

Uncovered RO/Di water is so ion free it will pick them up out of the air, it does not mean the water is bad any more it just give you a "false" reading on your TDS meter, the water was still pure when you made it but picking up the ions in the air will show TDS's on your meter, cat litter boxes close by are the worst cause of it.

I keep my basin covered. But I have had problems before with the basin collecting a static charge from somewhere, so could that also cause a false reading?

 

[tbittner]

You should circulate the water with the salt for 48 hours to make sure all the crystals are disolved. Undisolved crystals are very hard on animals.

 

[sasquatch]

according to Boomer the TDS meter reads charged ions, so? how come a TDS meter seems so important? are all bad elements in ro/di water charged? guess its just a measure of filter failure not quality?

 

[BobBursek]

Yes, even the florescent light ballast or compact fluorescent lights, the curly tube type can cause interference on a TDS and PH meters, best to take a clean vessel and take your reading away from them. 48 hours is excessive, 2-4hrs will be fine to gas of salt mix with surface agitation/air stone on a salt mix, just have it up to matching temp and PH, PH is more important then a degree or 2.

 

[BobBursek]

IF your water coming out of your RO/DI is 0 you made good water, now anything in the air might attach to the water, not anything bad but the meter will pick it up. So let say it is still 0, you add the salt mix still great water, but with your salt in it, meter it and it is off the scale. Tou have to understand what TDS is an abreveation for, TOTAL DISOLVED SOLIDS, your salt you added. But if the RO/DI is failing and not getting all the bad things out, they are TDS and that what your meter is reading, the meter does not discreminate between good things and bad, just tells you there are TOTAL DISOLVED SOLIDS in the water. Good CA, MG, bad Po4 trates, trites, your meter cannot tell the difference, just tells you there is something there. I hope that helps you understand TDS'S.

 

[BHenderson79]

IF your water coming out of your RO/DI is 0 you made good water, now anything in the air might attach to the water, not anything bad but the meter will pick it up. So let say it is still 0, you add the salt mix still great water, but with your salt in it, meter it and it is off the scale. Tou have to understand what TDS is an abreveation for, TOTAL DISOLVED SOLIDS, your salt you added. But if the RO/DI is failing and not getting all the bad things out, they are TDS and that what your meter is reading, the meter does not discreminate between good things and bad, just tells you there are TOTAL DISOLVED SOLIDS in the water. Good CA, MG, bad Po4 trates, trites, your meter cannot tell the difference, just tells you there is something there. I hope that helps you understand TDS'S.

Yeah, I understand that about TDS readings, which is why I assumed that the salt residue was the issue from the beginning. I suppose the best test I can do it to just disconnect the output hose from the RO/DI and run the first bit into a plastic cup when I make a new batch of water and I can test that.

 

[BobBursek]

It is called TDS creep, I always back flush my unit before and after useing, but when the unit sits for awhile the first few gallons will be higher in TDS then after 4 or 5, Ive been told why but can not remember the whole explenation, I do not worry about it. After awhile you will know your tank, salt mix, doseing amounts, and water changes and how they all interact. I am on 3 different Reef sites, and the most thing I have noticed is over reacting, not being atilyticle, keepijng notes and over reacting. AND look who post, in all forums, and look at there answers, you will learn who to trust and who are just an opion, and not all works the same for all.

 

[BHenderson79]

Is there a standard back flushing procedure for RO/DI units? Mine did not come with any sort of manual so there's been some trial and error for me to make sure it's working optimally.

 

[tbittner]

Yes, even the florescent light ballast or compact fluorescent lights, the curly tube type can cause interference on a TDS and PH meters, best to take a clean vessel and take your reading away from them. 48 hours is excessive, 2-4hrs will be fine to gas of salt mix with surface agitation/air stone on a salt mix, just have it up to matching temp and PH, PH is more important then a degree or 2.

Most of the experts that I read say 24 hours but it depends on the salt that your using too. Reef crystals takes DAYS to fully disolve.

2-4 hours isn't enough time.

 

[BobBursek]

I do not know what unit you have, but they are all the same, they cost about 12.00 at MD, they bypass your waste water line and no restrictor in it, I have seen them at HD by the water softener area, but you have to know how to pipe in in, I can tell you but, I am lisenten to Home Prerrie Companion till 7pm. I dose myself with Vodka not my tank, and then get the grill going for Lamp burgers.

 

[BobBursek]

TBittner,
Bad advice and info! I have been using RC since day one, 8am, turned on heater and pump in 30gal mixing tub, added RC over an hour to SG1.026, added MG and Ca to 1350-420 respectively with an air stone also, PH 8.0 at 4pm did a 30gal/ 20% water change like I do every 2 weeks, your 24-48 hours is a very conservative time.

 

[tbittner]

Better safe than sorry. I see a lot of undisolved crystals still floating around in the mixing barrel, even after 24 hours. The IO would disolve thoroughly in 12 hours though.

The undisolved cyrstals will rip the gills right out of a fish.

I'm not looking for an argument, I'm just repeating what I've read, and I'm passing along my personal experience with RC.

Is there a reason why you don't want to mix the saltwater for longer than 8 hours? Or is there a reason why we shouldn't mix it for that long?

 

[BobBursek]

I take the mixing pump hose and blow the bottom of the mixing tub to disolve any of those and what does not is a precip and not really undisolved salt.

 

[lcstorc]

I have one question though.
Does it do any harm to mix it longer? This is going to be particularly important to me sice once I get my new water set-up I plan to have 65g of pre-mixed water at all times. Obviously it will be mixing for even longer than 24 hrs.

 

[BobBursek]

Once mixed and gased off, you do not need to keep circulateing the water.