how Long Can I store Ro-Di Water In 25L Tubs In A Dark heated Cupboard?

David100 · Jan 23, 2023

I am looking into mixing my own salt as my LFS store only offers TMC salt and it doesn't allow me to boost my KH or PH via the salt mix, so im thinking of moving to the red sea mix, however, I dont have a RODI unit and even if I do I would need to us it outside on a hosepipe and its winter right now, so I was just wondering how long can I store RO Water for to mix salt into in the future? I have around 4-5 25L containers, Could I fill them all up and each week mix my salt into them for my water change? Or would that cause an issue?

They would be stored in the boiler cupboard which is right next to my tank, so its dark house temperature.

KStatefan · Jan 23, 2023

Why couldn't you use a RODI at your sink?

I make 50 gallons at a time and it probably takes a month to go thru that.

RandomUser7 · Jan 23, 2023

As long as it's sealed tight I think you can store it forever. I buy a jug of RO water every week and top off the tank daily. I've never observed any problems with the water.

PotatoPig · Jan 23, 2023

I’ve been assuming there’s no limit - there’s nothing to “go bad”. It’s sealed up, there’s virtually no biological material or nutrients in it to go bad, worst I can imagine is it de-oxygenates a little but that should be fine as you’re gonna mix it up when adding salt anyway.

Posting in case there’s a reason not to batch and store this stuff.

Only thing I can think is if you’re running a RODI system and batching, say, a few weeks worth then there’s potential for bacterial/etc growth in the RODI system as it’s not getting flushed.

David100 · Jan 24, 2023

PotatoPig said:
I’ve been assuming there’s no limit - there’s nothing to “go bad”. It’s sealed up, there’s virtually no biological material or nutrients in it to go bad, worst I can imagine is it de-oxygenates a little but that should be fine as you’re gonna mix it up when adding salt anyway.

Posting in case there’s a reason not to batch and store this stuff.

Only thing I can think is if you’re running a RODI system and batching, say, a few weeks worth then there’s potential for bacterial/etc growth in the RODI system as it’s not getting flushed.

Wouldnt this be resolved the very next time it's used and discarded via the drain water? Also wouldn't it dry out in a few days in a house? limiting opportunity for bacteria to grow?

PotatoPig · Jan 24, 2023

David100 said:
Wouldnt this be resolved the very next time it's used and discarded via the drain water? Also wouldn't it dry out in a few days in a house? limiting opportunity for bacteria to grow?

So the system is a series of sealed cups full of high surface area media that can absorb water across its surface. There’s no ventilation or route for evaporate to get out. It gets wet it stays wet.

Theres a few things working in your favor - the entry to the system is closed to any contaminants not already in the water, and there shouldn’t be many, the initial carbon blocks will absorb a lot of chlorine/chloramine so not a great environment for microbial life, and the later stages have very little nutrition in them so also not a great environment for microbes to live in, but probably not something you really want to leave alone for a long time either.

BeanAnimal · Apr 4, 2023

I had not done a water change in (easily) 5+ years. 50 gallons of RO/DI with some salt (no clue how much, maybe 1/3 concentration) sat for that entire time. Fired up a powerhead and a bag of carbon for a day or two and it is not plumbed into a dosing pump for SW replacement daily. The salt certainly helped prevent growth of anything.

Pure RO/DI? It may grow slime or bacteria at some point, but not likely if it is clean and sealed.