TDS readings

docjones · #1 01/07/2008, 08:42 PM

I am getting some algae on my sand bed or may Cynao (Spelling??) and I am wondering if it is my water. My TDS readings of my RO/DI water is 6, is this to high? I just up graded from a 55 to a 125 so I guess it could also be a mini cycle or something. But I do have a phosphate reactor on the way. So what do you guys think water or something else?

spamreefnew · #2 01/07/2008, 08:48 PM

a tds reading of 100 is good 250 is a bit hi but anything under 20 is great

tecoral · #3 01/07/2008, 09:05 PM

Quote:

Originally posted by spamreefnew
a tds reading of 100 is good 250 is a bit hi but anything under 20 is great

Uhhhmm, Not to be harsh or anything but no, thats really really bad. IME, 20 is not great, 0 is great. I start looking to replace my DI resine, at 5tds.

What kind or RODI are you using, have you back flushed the membrane? What is your tap TDS?

6 is marginal, it could be a problem if any of it is PO4, SI or NO3, anything over 10 is unacceptable IMHO.

Some of what you are looking at most certainly is the typical algea cycle of a new tank. I think if you address the RODI tds and give the tank some time it will resolve itself.

docjones · #4 01/07/2008, 09:16 PM

I have not back washed it, and it is a Filter Guys 75gpd RO/DI. Oe thing I did just do which is interesting is I put some RO water in a glass cup tested it and it was 1. I then tested my RO reservoir and it is 6. So I think the end result it I must have left some no RO water in it once I washed it out after the tank switch over. hopefully my water isn't the issue, I would hate to have to dump 50g of water of my TDS reading.

bower23 · #5 01/07/2008, 09:26 PM

tecoral is right on with his numbers... most people start replacing filters and resin around 6-7, if your filter is not old, it may not need backwashed yet. It's hard to tell if you are not sure if there was dirty water still in the tank at the time you filled it. I wouldn't worry too much. You should be ok with the water at 6... just make sure you clean it out and test the next batch.

Snowboarda42 · #6 01/07/2008, 11:43 PM

I keep my TDS below 1 personally

o.c.d. · #7 01/08/2008, 12:15 AM

I remember reading that R/O storage containers if left without a cover will pull gases and such from the air raising the TDS. I tried to find where I read it but I have to many books. Anyone else remember this and if so help me or it will bother me till I find it. docjones is your water sitting uncovered?

HBtank · #8 01/08/2008, 12:21 AM

When it comes to RO/DI product water, 0 ppm is recommended.

This is due to the fact that when DI is exhausted, it leaches undesirable things like P04 FIRST at a very high rate. 1 ppm might seem low, but not so much if you are considering P04 is recommended to be at .03 ppm in a reef tank.

DI should always be changed when it goes from 0 to 1 ppm

.

bower23 · #9 01/08/2008, 07:04 AM

I could see that if you were running a sps only tank... anything else, you will be fine.

64Ivy · #10 01/08/2008, 07:26 AM

Quote:

Originally posted by bower23
I could see that if you were running a sps only tank... anything else, you will be fine.

Not necessarily. I've seen some pretty nasty cyano outbreaks in 'softy' tanks due, in part, to high nutrient water. I'd try to get it down as low as possible.

m2434 · #11 01/08/2008, 08:23 AM

Quote:

Originally posted by 64Ivy
Not necessarily. I've seen some pretty nasty cyano outbreaks in 'softy' tanks due, in part, to high nutrient water. I'd try to get it down as low as possible.

I'm not saying your wrong, but I would suspect feeding or leaching from LR first... A single feeding could potentially raise P levels many times higer than that of the worst tap water.

Also, remember that even the best RO/DI filters only remove around 99%, maybe a little more if working perfectly, but 98% is still reasonable.

How much of that do you think is actually P, probably not much...

just my .02.

AZDesertRat · #12 01/08/2008, 09:59 AM

A TDS of 6 after DI is not acceptable. As someone pointed out earlier, DI resin releases weakly ionized substances when it nears exhaustion, it does not even wait until it is exhausted. A few weakly ionized substances are silicates and phosphates.
To really be able to answer the question though you need to provide tap water TDS, RO only TDs and RO/DI TDS numbers to determine how well your unit is working. You should be seeing a 96-98% reduction in TDS with RO only before DI and a 0 TDS reading after DI. If you are not getting that then you need to do further investigation as to why.

And the best RO/DI filters will remove 99.999% of the contaminants, heck my RO only with no DI is averaging 99.23%.

I don't know what they are referring to when they say "backwashed" but there is only one home use RO/DI unit on the market that I am aware of that has provisions to backwash. Some do include flush valves but if you have not been using it all along its too late now, dissolved solids have begun to solidify on the membrane and no amount of flushing with tap water is going to reverse that.

Pmolan · #13 01/08/2008, 10:15 AM

Filter guys are in the sponser forum if you wanted to post there since its a filter guys unit.

Randy Holmes-Farley · #14 01/08/2008, 10:46 AM

tecoral is right on with his numbers... most people start replacing filters and resin around 6-7

IMO, you are crippling the effectiveness of an RO/DI if you are going to let that much crap get through. The first things to break through an RO/DI are likely to be some of the things that you most do not want getting through (ammonia and silicate, for example).

I detail why you should replace the DI as soon as it rises above 0 ppm TDS in this article:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm

snorvich · #15 01/08/2008, 10:53 AM

I go with zero TDS coming out of my RO systems (I have two). If my TDS is greater than zero, I replace. Did you, perchance, notice what AZDesertRat does for a living?

realest · #16 01/08/2008, 04:17 PM

I don't have a tds meter to meter my tap water. But I do have a dual tds meter to meter my ro water and di water.

My unit is brand new, installed 4 days ago. The ro water is at 1ppm and di is at 0ppm.

I also got it from the filter guys. They are great and they have great support.

Pmolan · #17 01/08/2008, 04:23 PM

Hmmm. I have the dual monitor measuring the tap and the DI. I guess your way makes more sense. Monitor the RO then the DI.

AZDesertRat · #18 01/08/2008, 04:56 PM

Get a handheld TDS meter. Inlines are not as accurate and you lose the portability. Unless your water and air temperature are exactly the same the inline will be off since it measures air temps and not water. The error can be something like 2% for every degree C difference in the two.

tecoral · #19 01/08/2008, 06:08 PM

Quote:

Originally posted by Randy Holmes-Farley
tecoral is right on with his numbers... most people start replacing filters and resin around 6-7

IMO, you are crippling the effectiveness of an RO/DI if you are going to let that much crap get through. The first things to break through an RO/DI are likely to be some of the things that you most do not want getting through (ammonia and silicate, for example).

I detail why you should replace the DI as soon as it rises above 0 ppm TDS in this article:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm

Thanks Randy, I guess I will start changing resine even sooner than 5. Thanks for your input.

bower23 · #20 01/08/2008, 06:26 PM

I agree that 0 is the best and it is what we all should strive for... but do you really think this guy should dump a whole 50g tank because he is at 6? Come on... that is just overkill. I just spent 6 months low on cash and had to use my old RO unit at 22ppm and the only thing was a little extra algae growth on my glass. Everything else still did great... even my sps. Granted it's not something I would say is ok all the time and by all means try to run at 0. But to say anything over 0 and you need to replace your filters is just.... not realistic. You can listen you whoever you want.. and Randy, I know you know what you are talking about. But I don't think it is as important on a predator tank than it would be on a sps tank. I would take everyone advise but I also wouldn't freak out and dump all that water... just my 2 cents.

Pmolan · #21 01/08/2008, 06:32 PM

Quote:

Originally posted by bower23
but do you really think this guy should dump a whole 50g tank because he is at 6?

Hey wasted 150 gallons making it!! I agree that its a waste to dump it, but it can be replaced in a day.

m2434 · #22 01/08/2008, 06:52 PM

There are a lot of people using tap water with success, how high do you think that TDS is 250? 350? I agree that for consistency, using a TDS of 0 is better, but lets be realistic the TDS is 6... 60 I'd worry, maybe even 16, but IMO it seems a bit paranoid to think that this would really make or break the tank...

Heck many people have a TDS of 0 and still get cyano, as I said before, I think food is going to make much more of a difference.

I might buy the idea that he should be careful to only use 0 TDS water from now on, but dumping it all, seems a bit extreme, all things considered... Maybe don't feed for a week, run carbon, GFO and aggressive skimming and call it even

Many of the people responding certainly understand water chemistry better than me, so this is of course just my opinion FWIW...

bower23 · #23 01/08/2008, 07:20 PM

m2434- I agree. It all depends on what is in the tank. Someone with only softies and PC lights shouldn't really be that worried. If he has a 250g with all sps and twenty thousand dollars in his tank... then I'm sure he wouldn't have even had to ask the question. You just switched tanks.. which I'm sure that didn't help, shoot for a reading of 0, run the reactor for about a month, and all problems solved. Well, for now

.

Alaska_Phil · #24 01/08/2008, 08:54 PM

Back to the original topic, that is Algae, If you're worried that it's your source water then you need to test it for things that algae loves. Ammonia, Nitrate and Phosphate. The TDS tells you how much stuff is in your water, but not what it is. That could be 6ppm of calcium, which would be good. But if it's 6ppm of nitrate, that would be bad. Iron or copper would be even worse.

You might check your clean salt water too, I've heard some brands of salt contain nitrates or phosphates.

Phil

AZDesertRat · #25 01/08/2008, 09:29 PM

6 TDS after DI can very well be phosphates, silicates or nitrates as all three are weakly ionized and released by exhausted resin. TDS meters may not even register some levels of each but a conductivity or resistivity meter would.

The key is change the resin when you first begin to see anything other than 0 TDS.