DI vs one week aging for tap water

[Mihai]

I'm agonizing over purchasing a de-ionizer (DI) to treat the tap water
before I make salt water. I read (in several places) that if I
circulate the water for 1 week all bad things go away (at least the
chlorine and chloramine <i>do</i> go away -> I tested this). I know
that the opinions on the subject are split (some swear by R/O, while
others say that aged water is OK).

The primary question that I have is:

1) How and what can/should I test to make sure that the water is good to use
in the aquarium? (chloramine is obvious, what else, copper?)

The second questions:

2) Would a DI make a big difference in the quality of the water? I
know that an R/O + DI would, how about just the DI?

Thanks a lot,
Mihai

 

[hillbilly]

I would check the water for phosphate for sure. I think for most people, a good R/O unit is all one needs. I'm not a water expert, but I trust R/O to get my water as clean as it's going to get.

 

[ChrisRD]

Aging the water for a week will do nothing to remove many contaminants that are going to cause algae problems in your tank. That's not really one of the options for water purification.

As for using the DI - it's fine. The product water from a properly functioning DI unit should be just as good as the product water from an RO/DI unit. It's just going to be a lot more expensive over the long term to make water with a DI-only setup.

IMO an RO/DI unit is well worth the small up-front investment.

 

[Mihai]

It's just going to be a lot more expensive over the long term to make water with a DI-only setup.

Oops, why is that? I thought that an RO/DI is an RO + DI and hence it costs more than a DI-only... am I missing anything? And how expensive it is? My LFS offers 1gal of RO water for $.5, so is it worth it?

Thanks,
Mihai

 

[ChrisRD]

DI cartridges are generally expensive. If you get a refillable cartridge and order DI resin in bulk quantities you can get it cheaper.

In an RO/DI unit, the RO does most of the work and the DI just finishes things off. The RO membrane is very inexpensive to operate. So, in effect, you pay more up-front for the RO/DI, but it quickly pays for itself with much lower operating costs. How quickly this happens (the payback period) depends on how bad your input water is.

RO water is not quite as pure as DI or RO/DI, but it's the cheapest (again, long term). Depending on your input water, RO-only may be good enough.

One thing you should get no matter which system you go with, is a TDS meter. This allows you to check the purity of the water.

Buying from your LFS sounds like a good option, but I'd still check the water with the TDS meter to make sure you're getting what you pay for.

 

[ChrisRD]

FWIW, most people who stay in this hobby for any length of time end up buying an RO/DI unit. In the end, most seem to feel it's the most convenient and cheapest way to get ultra pure water.

 

[Archmage]

I use the Tap Water Filter from Aquarium Pharmaceuticals Inc.

The unit is a simple unit that costs 50 dollars. It makes deionized water about 60-100 gallons per cartridge. Each replacement cartridge costs $17.99. Very economical and water is very very pure.

 

[Anonymous]

I used that system for a while also, and though it worked fine. Never really tested the water though.

Now I use a plain RO system, works great.

 

[Anonymous]

Well you can buy an RO unit for between $150 (crappy) and $300 ... I know that's a lot of money but in the face of how much the reefkeeping hobby costs (add up the dollar amounts sunk into your tanks, lol, you know what i mean) ... it's not that bad.

I consider good water a foundation of a successful aquarium (freshwater or saltwater). Because of that, I felt it necessary to purchase an RO unit.

Don't put tap water in your reef, even if the tap water is aged.

Try this instead:

Start by purchasing jugs o' filtered RODI water from your favored local pet store. A nickel per gallon isn't bad at all. It's also a good idea to test the water for phsophates once, just as a check to see if the store is selling good water. See how long that lasts before you get sick of hoarding empty plastic jugs, lugging them around and making trips to the pet store all the time.

Then buy an RODI filter.

 

[ChrisRD]

I use the Tap Water Filter from Aquarium Pharmaceuticals Inc.

The unit is a simple unit that costs 50 dollars. It makes deionized water about 60-100 gallons per cartridge. Each replacement cartridge costs $17.99. Very economical and water is very very pure.

The TWPs work fine and, being a DI unit they'll produce very pure water. Just as good as RO/DI and maybe slightly better than RO. The numbers you've posted, however, are the very reason a lot of folks end-up with an RO or RO/DI unit.

At $18 per cartridge and say an average of 75 gallons per cartridge (and this can vary greatly - I've lived in places where I was getting 30 gallons per cartridge from the same unit because of the hard tap water) that works out to about 24 cents a gallon for water.

With an RO unit you can make purified water for literally a few cents per gallon (over the long haul). If you have a large tank, the RO unit will pay for itself very quickly...

 

[Archmage]

ChrisRD,

You're right. Since I only have a 30 Gallon Cube tank, I opted to get the TWP for 1. Convenience
2. Ease
3. Relatively cheap compared to the other units (less upfront costs)
4. Purity of water

Looking at it for usage in a large tank, I can understand why you guys went to the other units.

 

[Jolieve]

msichiti: Get a report of your water quality from your local water utility, they are required by federal law to give you this if you ask for it. It will list everything that is in your tap water.

If you need help interpreting that report, you can always come back to this forum and we'll help you figure out exactly what's in there. I'll bet, that once you get your water report, you'll want an RO/DI unit, because you'll be scared to drink straight tap water!

J.