# RO and RO/DI



## blurry (May 10, 2010)

Im trying to wrap my head around RO and RO/DI, whats the real difference between these 2 beside that the DI cost more? Is it ok to just have RO water in a salt water aquarium or do you have to use DI also? Also how long does the cartridges last for?
Sorry for the noob questions.


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## gklaw (May 31, 2010)

Besides the little bit more on initial investment. An additional cartridge is $30. It last me for over 1 year on my 250g+ gallon open top system for top up with the occasional may be twice a year WC. The exact science aside, I honestly make this a feel good factor.

I think Anthony use tap water and prime for his SW WC. I figure prime is not exactly cheap either. With RO and DI in auto-top up. The beauty is I don't even look at the thing for months. I do try to change the prefilters and carbon cartridge every 6 months. Membrane are 2-3 years plus.


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## dino (Aug 29, 2011)

this is easy I think if im correct ro/di is zero tds meaning no comtaminents and thats what we want


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## Dietmar (Dec 15, 2011)

Here in Surrey, our water has a TDS of 10-15, depending on the season. The RO part of the filter will bring this down to close to 0 or 1 depending on how much throughput you have on your filters. 
The DI part will bring the TDS down to 0. If you only had a particle filter and the DI, you would still get 0 TDS until the DI became depleted, Which would happen faster without the other filters in the RO part. DI is more expensive so one would make use of the other filters first. 
I use a colour changing DI and with my 50 gal aquarium, with a lid, my DI lasted about 6 years.
As Gordon said, with our good water here in the lower mainland, the DI is a "feel good" kind of thing. Would I go without DI? No, I feel good using it. If my RO membrane crapped out, then the DI would take over and still give me a reading of 0 TDS


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## JTang (Apr 21, 2010)

I know someone in Yaletown runs a beautiful reef tank for years using tap water only. No algae or Cyano! As for myself, I use only RO. Nothing fancy but works for me...


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## neven (May 15, 2010)

since i am on the coquitlam reservoir i haven't been a stickler on the di water only in my reef. Since i dont have my DI filter connected to anything permanent and am stuck using the shower to connect the filter, i have to guard the water buckets being filled from the kids and have a royal pain of a time moderating the flow. I only have a DI cartridge thats just about past its life so i get around 1-2 ppm afterwards, too lazy to replace for now  So prime and tap water it is


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## slakker (Apr 12, 2013)

^ same... I have a RO/DI unit and with a TDS on it, the in is about 11 ppm and out is 0 ppm. But I've used tap in a pinch before and have not noticed any problems. With more and more water meters going in, I may take out the system... RO (with or without DI) is horribly inefficient... it take 3 to 4 gallons of water to make 1 gallon of RO water. The rest just goes down the drain... unless you can use the water for something else like washing cloths, gardening, etc... but then you're into a water collection/recycling system as well...


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## blurry (May 10, 2010)

Is there a way to tell how much tds is in my tap water? Im just not liking how it takes 12 hrs or so just to fill up at 50 gallon holding tank with a 100 gpd RO/DI system. Im swaying on not to get an RO system since ive notice most people that have the system doesn't have clean water like we do in BC.


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## JTang (Apr 21, 2010)

blurry said:


> Is there a way to tell how much tds is in my tap water? Im just not liking how it takes 12 hrs or so just to fill up at 50 gallon holding tank with a 100 gpd RO/DI system. Im swaying on not to get an RO system since ive notice most people that have the system doesn't have clean water like we do in BC.


I check mine with a TDS meter. You can get one off eBay for under $8.


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## neven (May 15, 2010)

i was patient and got mine from DHgate, after 20ish days i got one for even less without paying shipping 

my TDS has been between 8-14 ppm out of tap, in the summer months its lower end, and it rarely is 14, mostly its 10-12


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## gklaw (May 31, 2010)

Rob needs to start a group buy from DHgate


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