pH Before and After RO-DI Installation

[Salty Sphynx]

Thought I'd just post to a new topic instead of derailing the anoxic filter thread (and I haven't actually started constructing my BCBs yet anyway).

Anyway, We've just finished plumbing in the new Aquatic Life RO system with DI cartridge, and here you can see the results of the before and after of our pH readings.

The TDS went from 226 to 0.00 as well.

It's a bit slow, but current output is 1 gallon per 25 mins... not too terrible as this will be solely for the aquarium.

So far, I am very encouraged at what this RO will do for the tank and can't wait to get to cycling.

Does anyone else use this system? If so, approx how many gallons do you get prior to having to change filters?

[Adam S]

How many gallons? Not sure. Membranes can last 1-5+ years, depending on how much you baby them. Changing the sediment/carbon filters as needed and not having liquid rock to begin with all help extend the life of the membrane. Also, never use hot water. When the TDS starts creeping above 10 or so, it's time to get a new membrane. Most non-reef people don't bother with DI, as it's not really necessary for freshwater use.

[Salty Sphynx]

How many gallons? Not sure. Membranes can last 1-5+ years, depending on how much you baby them. Changing the sediment/carbon filters as needed and not having liquid rock to begin with all help extend the life of the membrane. Also, never use hot water. When the TDS starts creeping above 10 or so, it's time to get a new membrane. Most non-reef people don't bother with DI, as it's not really necessary for freshwater use.

It's the 50 gallon 4 stage filter, for my 92 gallon tank.

I remember during my brief stint in the water treatment industry that those membranes lasted as much as 5 years; I doubt will last that long here. It is plumbed in to the cold water side of my washer, with a dedicated line.

Our water here in FL is off the chart hard and pH always very high due to extreme limestone content. Our further desire was to eliminate the chloramine.

The RO-DI was recommended by fellow local freshwater hobbyists, so am assuming that recommendation is based on the overall picture of our existing water parameters and where we ultimately desire to be with discus.

[Adam S]

226 TDS is nothing... fine for most fish unless you are trying to spawn something.

[Hart24601]

I use RO/DI for all my FW fish. Here in Iowa if you are not using at least RO you better not be doing waterchanges much with tap water or eventually your fish will die off. I have seen it so many times locally, mystery losses after W/C despite using conditioners. There is so much ag run off and a heavy rain during planting really messes with the water. They add lime to burn off organics, but who knows what all makes it past, they don't test for everything.

Anywho, I get years out of my membranes, I currently use the bulk reef supply watersaver dual membrane system and have been happy with it the past 3 years, I used various systems before that but not really a "kit".

[Salty Sphynx]

I use RO/DI for all my FW fish. Here in Iowa if you are not using at least RO you better not be doing waterchanges much with tap water or eventually your fish will die off. I have seen it so many times locally, mystery losses after W/C despite using conditioners. There is so much ag run off and a heavy rain during planting really messes with the water. They add lime to burn off organics, but who knows what all makes it past, they don't test for everything.

Anywho, I get years out of my membranes, I currently use the bulk reef supply watersaver dual membrane system and have been happy with it the past 3 years, I used various systems before that but not really a "kit".

Thanks for your input.

Do you have to change the DI cartridge frequently? I've only produced about 20 gallons so far (since installation) and I'm already starting to see a bit of a color change on the DI. :confused:

[Hart24601]

I have a dual DI setup, but my tds post membrane is around 3 if I remember right andy DI lasts quite a while. We must not have much co2 in the water. I don't know how long it lasts but I don't change them more than every couple months. I use refillable cartridges and media from bulk reef.

[DJW]

Do you have to change the DI cartridge frequently? I've only produced about 20 gallons so far (since installation) and I'm already starting to see a bit of a color change on the DI. :confused:

Dissolved CO2 in the feed water isn't rejected by the RO membrane because its a gas, so it goes right through and gets caught by the DI. If you have a lot of CO2 in your water it wears out the DI resin pretty fast. CO2 doesn't register with a TDS meter, so the best way to know how much CO2 you have is to compare the pH to the KH. Another way to get a sense of whether you have a lot of excess CO2 is to look at what the pH of your tap water does as it ages. If the pH of the tap water goes up it indicates excess CO2, and the more it swings the more CO2 you have.

My well water has a tremendous amount of CO2. I tried DI once for the fun of it and it was wiped out in 2 or 3 days.

https://www.aquaticlife.com/blog/how-co2-can-impact-di-resin-consumption/

To use the calculator linked below, it is very important to enter the pH of the tap water as measured right out of the tap, don't let the water sit around before measuring.

https://www.hamzasreef.com/Contents/Calculators/CO2DIDepletion.php

[DJW]

... by the way, DI is a salt water thing. Only in the rarest cases would it be a benefit for freshwater.

[Hart24601]

I was under the impression that nitrate is poor rejected by ro membranes (relatively speaking I think I saw 85% and 75% in a study) so DI can still be applicable.

[DJW]

I think RO gets about 90-95% of the nitrate, but that's an interesting thought... I'll check on it. I have a lot of nitrate, which is partly why I tried using DI, now that I think of it.

[Salty Sphynx]

I was under the impression that nitrate is poor rejected by ro membranes (relatively speaking I think I saw 85% and 75% in a study) so DI can still be applicable.

My understanding as well.

Additionally, those that recommended the RO/DI combo for the discus tank advocate that the DI cartridge is beneficial for water supplies with a high chloramine content (which ours is).

[Megalodon]

... by the way, DI is a salt water thing. Only in the rarest cases would it be a benefit for freshwater.

Except if you have chloramine then you need DI to mop up the ammonia.

[DJW]

Except if you have chloramine then you need DI to mop up the ammonia.

If you have CO2 wouldn't it be cheaper to use Prime? I was amazed how quickly the DI resin was depleted. I make 100 gallons a day of RO... I'd go broke paying for resin.

[Megalodon]

If you have CO2 wouldn't it be cheaper to use Prime? I was amazed how quickly the DI resin was depleted. I make 100 gallons a day of RO... I'd go broke paying for resin.

Yeah, it would be a lot cheaper.

[Hart24601]

Just because of where I live and the apparently low amount of CO2 in the water DI costs for me are pretty low - plus I use the water for a reef too. If I am going to run the RO might as well drop the money on DI. $55 for 7.5 lb (to overfill 6 cartridges) lasts me at least 6 months and might even be longer now as I am slowing down my automatic water changes now that the fish are 6".

[Salty Sphynx]

Just because of where I live and the apparently low amount of CO2 in the water DI costs for me are pretty low - plus I use the water for a reef too. If I am going to run the RO might as well drop the money on DI. $55 for 7.5 lb (to overfill 6 cartridges) lasts me at least 6 months and might even be longer now as I am slowing down my automatic water changes now that the fish are 6".

I'm envious.

Our CO2 is off the chart. :(

[DJW]

There is a way around the CO2 if you wanted to take out ammonia or that last trace of nitrate. Set up an ageing barrel for the RO on a high stand or in the rafters. It has an airstone but no heater. After 12-24 hours the extra CO2 is gone, then open a valve and gravity flow through DI to a storage barrel. If the TDS of the RO is low the resin should last long enough that the cost doesn't outweigh the benefit by much. Its hard to find data on how well RO membranes remove ammonia, but years ago there was a simply member here (RandalB) who was a filter expert, who said that RO should remove around 70% of ammonia. This should be easy to verify, but I can't test it since I don't have chloramine.