RO DI add-on

[DonW]

I have a older Kent RO unit with just three stages. I saw a DI add-on unit last night. Does DI make a difference? Is the DI part worth the extra money?

Don

 

[mattseattle]

in my experience the DI didn't add anything to my RO/DI unit. I actually took the DI filter out. I purchased a TDS meter to test the input of the water, the output after the membrane and output after the DI cartridge. The TDS input was around 36 - 40 most times, after the membrane it was 0 and after the DI cartridge it was 0. I thought if I was receiving 0 after the membrane why waste a DI cartridge so I just removed it.

I would buy a TDS meter and test it. I bought mine from Marine Depot for like 25.00 bucks or so.

 

[j.stagner]

There are things in the water than may be removed by the DI cartridge that do not show up on a TDS meter (chloramine for example), as evidenced by the fact that the DI cartridge shows visibly over time that it is removing substances by changing colors.

If the previous poster's TDS meter is accurate, though, it may be that companies like Kent and SpectraPure are scamming a lot of money from hobbyists like me who pay extra for the "Silica Buster" cartridged that are advertised to remove extra silica.

As for me, I believe that the DI cartridge is quite useful and would recommend that it be used. FWIW.

 

[mattseattle]

well my thoughts were if the TDS meter read 0 then the water was ok for use in a reef tank. my TDS meter has been calibrated....actually i did it twice to make sure my readings were accurate.

i guess i'm not knowledgable enough to know if the membrane and/or carbon/floss filters remove chloramine or not.

i also figured that the DI was overkill if I was getting a 0 reading right out of the membrane.

anyone else have thoughts?

 

[j.stagner]

The carbon filters do remove chloramine, at least initially. See the following link for the article on which I based my statement :

http://reefkeeping.com/issues/2003-11/rhf/feature/index.htm

mattseattle, Even if there is some question as to the utility of the DI cartridge, since you already paid for it I would say no harm done to use it.

What might be interesting is to start a poll (or is there one here already) about which hobbyists do or do not use DI on their water supply. Whether there is hard evidence or not, I would like to see what the very successful people are using....

 

[DonW]

According to Kent tech. TDS meters are just reletive to your system and calibration. They are by no means acurate and are just telling you if your particular system has declined.

Don

 

[mattseattle]

reading the City of Seattle Water Quality report it shows they use Chlorine which shows to break down quicker and is more easily removed using a carbon and membrane filtration. who knows if the report just lists Chlorine when they may be using chloramine.

i guess for safety purposes if you have a DI cartridge just use it as a precaution. i've been using my RO unit without the DI for going on 5 months now and so far no issues.

 

[mattseattle]

was Kent Tech talking about the TDS meter that is built into their units or the hand held TDS meters like I'm using which you can calibrate and all? i would imagine they are talking about their built in ones and not the hand held units.

 

[DonW]

I may be wrong but I think a tds meter measures conductive properties of water.So basicly there is no way for it to tell if chlorine, floride or phosphates are present. But it can tell you if your filter is passing things such as lead or copper. So it really just tells you your sediment filters need to be changed.

Don

 

[j.stagner]

DonW, I am pretty sure you are absolutely correct about the TDS just measuring conductivity.

I am sure there are hundreds, maybe thousands, of hobbyists running straight RO water without using DI, and having fantastic results. There are also people who use nothing less than glass distilled water for their tanks....

The DI add-on I saw was less than $30, so if it was me I'd probably try it. Of course, it's probably unlikely that you will see any real difference, particularly if you are not currently experiencing any problems.

One interesting thing to note about my system, the TDS meter is hooked inline between the RO membrane and the DI cartridge, so the reading is always *before* the DI. I wonder why they put it there? One rationalization is that when the TDS meter indicates the need to replace cartridges, the DI may assist in keeping water quality okay until I can order replacements.... Just thinking.

 

[UnresistibleBlu]

Remember not to use the TDS meter as an indicator of when to replace your sediment and carbon cartridges. Use it as an indicator for your RO membrane and DI resin only.

Blue

 

[j.stagner]

Yeah, that is a good point. Come to think of it, I've never changed my sediment or carbon, since my first RO/DI unit broke and I simply purchased a new one which is only a few months old.

What kind of schedule (roughly) should be used when determining when to replace them?

 

[UnresistibleBlu]

Yeah, that is a good point. Come to think of it, I've never changed my sediment or carbon, since my first RO/DI unit broke and I simply purchased a new one which is only a few months old.

What kind of schedule (roughly) should be used when determining when to replace them?

A reasonable rule of thumb is every six months. However - use your pressure gauge to tell when the filters are plugged, and also keep in mind the chlorine capacity of your carbon block. Some are rated at 2000 gallons, some at 10 times that amount.

Blue

 

[Nautilus]

Remember not to use the TDS meter as an indicator of when to replace your sediment and carbon cartridges. Use it as an indicator for your RO membrane and DI resin only.

Blue

Sorry but you guys must have some fantastic water up in Seattle area.
The TDS meter does show the user when it is time to change sediment or carbon filters of the unit.
For 2 years now it has let me know (I change mine when it reads 4 to 6 TDS) and only have changed the sediment and carbon filters and the reading goes back to 0 after I have done this. I have changed my DI filter 3 times now and use a hand held TDS meter for that indicator when to change it also.

 

[Nautilus]

the 2 carbon pre filter stages will remove the chlorine.

RO's always have carbon, and the carbon removes chlorine and chloramine. A DI alone won't touch those.

RO's also remove organics that DI's let through.

Finally, the DI's will be shot very fast by running tap water right into them. RO's extend the life of the DI by a factor of more than 10.

The carbon filter on an RO/DI or Ro only will break chloramine apart, but some of the ammonia will pass through an RO, being caught by the DI filter.

I say that the combo of the RO/DI unit it the best way to go so I can sleep at night.

Interesting link.
http://reefkeeping.com/issues/2003-11/rhf/feature/index.htm

If you let the water run for 5-10 minutes before collecting it. This will greatly reduce the likelihood of getting a high copper or lead level from water that has been sitting in your pipes for an extended period of time.
http://www.advancedaquarist.com/issues/jan2004/chem.htm

By the way please read this article by Randy H-F on TDS meters
http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.htm


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