Using DI resin to produce soft water?

[LordJoshaeus]

Hi everyone! Another question that does not directly relate to reefing but could be useful later if I set a reef up...I am seeking to set up a blackwater tank with virtually no hardness, TDS as close to zero as I can get, and a PH somewhere between 4 and 5.5. As the blackwater tank is not going to be larger than a 10 gallon (excluding a possible refugium), I don't want to spend money on an RO unit yet (plus...I am not too keen on a device that can take 15-30 minutes just to produce a single gallon of water and requires your constant attention that entire time).

Anyhow...I am thinking of using DI resin to soften my 45 ppm TDS tap water. While this would be more expensive per gallon than an RODI unit, it would also be far less tedious. What I would most likely do is put the water in a bucket and install a pump that will push water through the filter media for a day (I was originally planning on making a homemade zero water filter and pour water directly through that, but I thought that using a pump would be more thorough) before I change the filter to the next media. My goal is to get water with a TDS of 6 or less. On day 1 the pump will push the water through some cuprisorb and purigen, and the next day I would use the DI resin. How does this sound? Thanks

 

[Onewolf]

It sounds to me like you should go ahead and purchase a RODI system.

Target PH of 4-5.5 seems extremely low even for blackwater tank.

 

[LordJoshaeus]

I used a very small (think around a 40th of an 8th of a teaspoon) of sodium bisulfate per gallon of distilled water to achieve such low PH in the past. However, even a water distiller costs about 30 cents a gallon around here due to electrical costs, and if my idea works it will cost about half that.

 

[redfishbluefish]

It sounds like what you want to do is the same the old Kati/Ani system did. They were basically large canisters of cation and anion resin that purified your water. To regenerate you fill with either HCl or NaOH, and then you're good to go again purifying the water. Not sure if these are still available, but believe if you look around you could DIY something similar.

 

[LordJoshaeus]

I forgot to mention a few details!

- The tank will have 4 gallon WC's a week if a 10 gallon
- I was thinking of using coconut shell activated carbon and matrix carbon (a microporous carbon and macroporous carbon, respectively) instead of the purigen (may still keep the cuprisorb since I know how much metal it absorbs). How do you guys think that would work? Which would be more effective and/or practical?
- I was going to extend the resin's lifetime by supplementing my tap water with rainwater when it is available. Obviously it will need to go through some activated carbon first before I can put it through the DI resin (should I bother doing that?)
- Would there be anything wrong with me slowly pouring water through a container with activated carbon a few times, then doing the same with pouring it through the DI resin? Would be less time consuming than the pump method...