Does TDS really need to be zero?

[Fliger]

I finally got my RODI up and it has made life a lot easier. I was getting zero with 3 different TDS meters. Its now starting to creep up to 3, 4, 5. Is that a huge deal? For topoff I run it thru a kalk reactor so it probably doesn't make a difference - but what about for water changes?

Do most SPS'ers use zero TDS water only?

Thanks in advance!

David

 

[sfsuphysics]

I don't have zero TDS, but then again I'm too lazy to calibrate my TDS meter so I simply use it as a baseline for when something really wrong happens. What I would do is take a reading after the membrane and use that as a baseline.

 

[Fliger]

Hey Mike, I have the TDS meter inline - then I check with two more after fill my container. I'm sure the higher readings are correct - as it reads the same on all. I'm just more curious if its ok to have a small TDS reading - if folks really think it makes a huge difference.

 

[Jovreefer]

I have never changed mine until I get into double digits.

Also test before the DI and again after the DI ... you'll get 2 different readings ... if before the DI your getting insane high readings just replace the other cartridges and see if the reading goes back down to 0. If you take proper care of them the DI should last longer than the other filter parts if I remember correctly.

 

[Wiskey]

Mine is 0, stays that way for about 2 months even with the terrible AZ water. It creeps up around 1 after about 200 gallons made and I change the DI resin.

HTH,
Whiskey

 

[64Ivy]

I've had pretty good cyano outbreaks with a TDS as low as 6 ppm. Since then, I make sure to change my cartridges at 1 ppm.

 

[twon8]

actually i belive the ro will last the longest, up to two years, you should change the prefilters every six months, maybe more if your water is particularly dirty. with better carbon blocks and prefilters your ro will do a better job, thus extending the life of your di.

 

[Amphiprion]

It isn't really necessary for it to be zero (but it helps). Reasonably good quality water has a TDS of 10 or below (for aquarium use).

 

[ReeferAl]

The importance of low tds readings depends somewhat on what is in your water to begin with. A disproportionate amount of phosphate goes through the RO membrane compared to other ions. The DI resin removes that phosphate, but phosphate is not bound as tightly to the DI resin as some other ions. DI resin is an "ion exchange" resin. When the resin starts to get filled up it will start exchanging loosely held ions for those that attach more tightly. The result is that phosphate will begin being release back into the water. That 5ppm tds reading may then be mostly phosphate.
So, those that have low phosphate levels to begin with may see less of a problem from tds readings of 5 or 6 than those whose water starts with alot of phosphate. Personally, I aim to change my resin when it goes above 5, but I often forget to check and it gets higher.

Allen

 

[Amphiprion]

<a href=showthread.php?s=&postid=7789785#post7789785 target=_blank>Originally posted</a> by ReeferAl
The importance of low tds readings depends somewhat on what is in your water to begin with. A disproportionate amount of phosphate goes through the RO membrane compared to other ions. The DI resin removes that phosphate, but phosphate is not bound as tightly to the DI resin as some other ions. DI resin is an "ion exchange" resin. When the resin starts to get filled up it will start exchanging loosely held ions for those that attach more tightly. The result is that phosphate will begin being release back into the water. That 5ppm tds reading may then be mostly phosphate.
So, those that have low phosphate levels to begin with may see less of a problem from tds readings of 5 or 6 than those whose water starts with alot of phosphate. Personally, I aim to change my resin when it goes above 5, but I often forget to check and it gets higher.

Allen

That is entirely true. I had forgotten to mention that one. We have relatively low phosphates in my area, so I didn't think much of it.