TDS Readings

[PotomacBoater]

I just bought a "used" RODI unit

Optima Chlorimine Advanced by PureH2O

 

It has a Sediment Filter

a 1 micron Carbon block

a catalytic carbon filter for Chlorimine

the RO membrane

and the DI Resin

 

I'm getting 176 TDS in

and 2 tds out.

 

I don't have a hand held meter, this is from the built in meter

 

Whether I test after the RO Membrane OR after the DI, I still get 2 tds

I assume this means that I need to replace the DI?

 

(I have no idea how old any of the filters are ... I guess I could replace them all, but if its down to 2 already, I don't want to "waste" money)

 

Which membrane is the one that restricts GPD?

Can I look at the mebrance and know if its rated for 75, 100 or 150?

 

Thanks,

 

Matt

 

 

[hypertech]

Yes, that would mean its time to replace the DI.

 

There is only one membrane and its the RO membrane. The rest are filter cartridges.

 

If you don't seem anything on the membrane, you could look at teh flow restrictor. It might have a label indicating what the flow rating for it is.

Edited July 20, 2012 by hypertech

[zygote2k]

I disagree that you need to change the DI when it reads "2". As a general rule, I have been waiting till the OUT is 10% of the IN. You have 176 IN and therefore can wait till it hits 17 OUT before changing. I've not noticed any difference in water chemistry by waiting this long.

I usually will change the prefilter and carbon at this point as well.

[Origami]

The only thing to consider is that, when DI resin is exhausted, it begins to trade out the lower affinity ions that it's adsorbed, for higher affinity ions that are in the water stream. That means, the water quality going into the resin can be different than that coming out of the resin. Randy Holmes-Farley described this in an article that he wrote for Reefkeeping magazine in May 2005:

 

"when a DI resin becomes depleted, that does not simply mean that the water passes through just as it came from the RO effluent. It may actually be much worse from an aquarist’s perspective. The reason for this is that while the DI resin is functioning properly, all ions will be caught. But when it is depleted, not only the new ions are coming through and might show up in the product water, but so are all the ions that ever got into the DI resin in the first place. The total concentration of ions coming out of the exhausted DI resin will not be raised as compared to the RO's effluent, but which ions are released may be very different.

 

"In the DI descriptions above, I did not address the fact that some ions will show a greater preference for attachment to the resin than will others. When the resins are not depleted, it does not matter what the ions’ affinity is, as all are bound. But in a depleted scenario, when there are more ions than ion binding sites, those with a higher affinity for the resin will be retained, and those with a lower affinity will be released. It turns out that silicate is found at the lower end of affinity for anion resins. Consequently, if the DI resin has been collecting silicate for a long period and is then depleted, a large burst of silicate may be released.

 

"Perhaps even more of a concern is ammonia. In a system with chloramine in the tap water, the DI resin will serve the important function of removing much of the ammonia produced by the chloramine breakdown. Ammonia has a poorer affinity for many cation-binding resins than do many other cations (e.g., calcium or magnesium). Consequently, when the DI resin first becomes depleted, a big release of ammonia from and through the DI resin is likely. I recently had a DI resin become depleted, and the

effluent contained so much ammonia that I could easily smell it."

 

The bottom line is to plan on replacing your resin when exhaustion becomes evident.

[PotomacBoater]

In that case,

what is the indicator of the Resin being depleted?

 

Any increase in TDS

or 10% as mentioned earlier?

 

Does Resin "slowly deplete" or is it simply "On/Off"

 

 

 

 

 

[Origami]

When you start getting non-zero TDS out of the DI stage, it's starting to deplete. So, I'd start planning on changing it out now. It's not urgent, but it's prudent to not let it get too far because, while you know something is coming out of that stage, you don't know what it is.

[hypertech]

I disagree that you need to change the DI when it reads "2". As a general rule, I have been waiting till the OUT is 10% of the IN. You have 176 IN and therefore can wait till it hits 17 OUT before changing. I've not noticed any difference in water chemistry by waiting this long.

I usually will change the prefilter and carbon at this point as well.

 

So, if my in is 800, its OK to supply my aquarium with water of 80 TDS, but if my in is 200, then its only OK to supply my aquarium with water of 20 TDS? That rule doesn't make any sense.

 

Once you start having a reading, its time to change it. Its not an emergency or anything like that, but its near or at capacity and its time to change it.

[Buckeye Field Supply]

So, if my in is 800, its OK to supply my aquarium with water of 80 TDS, but if my in is 200, then its only OK to supply my aquarium with water of 20 TDS? That rule doesn't make any sense.

 

Once you start having a reading, its time to change it. Its not an emergency or anything like that, but its near or at capacity and its time to change it.

 

 

This is right on the money.

[Buckeye Field Supply]

It has a Sediment Filter

 

what is the pore size?

 

 

a 1 micron Carbon block

a catalytic carbon filter for Chlorimine

the RO membrane

and the DI Resin

 

The carbon block should be AFTER the Cat GAC

 

 

 

Matt - pull the membrane out and you should see a sticker on it. Should have a code something like "TW-1812-75" Where "75" is the gpd rating.

 

 

 

Russ

[Steve175]

Above zero and it is time to change.

[PotomacBoater]

This looks like the system I have ...

 

http://www.purelyh2o.com/index.php/h2o-test-meters.html?page=shop.product_details&flypage=flypage.tpl&product_id=67&category_id=80

 

First picture shows the full unit

second one shows the individual filter cartridges

and their order (right to left)

 

I have zero confidence that this was put together correctly before I got it

 

The sediment filter is 1 micron

and so is the carbon block

 

reading the website description is shows the Catalytic third

Do we think that is incorrect?

 

The RO Membrane says 75 GPD

Everything I read says the 100 gpd units are worthless

and I think 150 would be overkill for me, so I guess I'm staying with this one

 

Thanks for all the help!

[Buckeye Field Supply]

This looks like the system I have ...

 

http://www.purelyh2o...&category_id=80

 

First picture shows the full unit

second one shows the individual filter cartridges

and their order (right to left)

 

I have zero confidence that this was put together correctly before I got it

 

The sediment filter is 1 micron

and so is the carbon block

 

reading the website description is shows the Catalytic third

Do we think that is incorrect?

 

The RO Membrane says 75 GPD

Everything I read says the 100 gpd units are worthless

and I think 150 would be overkill for me, so I guess I'm staying with this one

 

Thanks for all the help!

 

 

Can't tell from your pictures but does that inline taste and odor filter (above the membrane) come AFTER the DI? If so, remove and discard it - it's doing more harm than good. Yur water is as clean as your system can make it immediately after the DI. You'll add TDS by running DI water through carbon - and you are wasting your money.

 

Keep a close eye on the male threads on those clear housings. They are prone to crack. This is a good example of why I cringe when I hear people say "all RODI systems are alike." Absoluetly not true. Those housings for instance are very very inexpensive on the wholesale market, but we won't use them.

 

 

 

Russ

[Buckeye Field Supply]

Also keep an eye on that clear RO membrane housing. Those always seem to develop cracks as well. I don't think even Purelyh20 uses them any more.