RO or tap filter?

vaderbanger

vaderbanger

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Dec 1, 2005
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is there a difference in RO water compared to tap water that is filtered through a basic water filter kit sold at home depot??
can a regular tap water filter be used in water changes for a saltwater tank instead of an RO??
sorry if i seem naive this is all new to me :D
 
Disclaimer: I'm a relative newbie myself, so don't take everything I say as 100% accurate.

That said, I've pondered over this topic quite a bit over the past several weeks. While I don't know about the water filters at Home Depot that you referred to, regarding RO vs. tapwater, the quick answer is, "tapwater probably contains all sorts of nasty stuff that may harm the residents of your aquarium, especially if it's a reef tank."

From what I can gather, the vast majority of reefkeepers use RO, but there are some FO / FOWLR-ers who use tapwater.

Is your tapwater suitable for SW aquarium use? You can take a sample to a fish shop to have it tested (or test it yourself if you have the kits). When I did this, my water had a nice high pH and no nitrates (good), but very high phosphates (bad... causes algae blooms). I could have run phosphate remover in the sump, but I decided to go ahead and install an RO/DI unit to remove source water quality as a potential problem-causer. I'm new at SW aquariums... I need all the help I can get!

So, the bottom line is that if you are on the fence as to whether or not to get an RO/DI, have your water tested and/or contact your local water company to find out what's in your water, then you'll have the info needed to make a decision.

If you do decide to go RO/DI, units can be found on eBay at very reasonable prices. I picked up a 100gpd unit for about $100 from this seller.

--Mike
 
I use tap water. We have a system on our water but I never have salt in it so it is plain ole tap water coming out. Knock on wood, we haven't had any problems. Nobody I know with tanks (salt and fresh) have used anything other than tap water. One salt tank ran for 10 yrs with no problems with tap. from different areas as well. It's simple enough to get tested if it concerns you. We've had our water tested and it has always been fine. We have city water though, not sure if well water is different.
 
macphoto may claim newbie status, but I agree with his post. First it depends on what you want to do with your tank. If FO,you may be able to use tap water. If a reef, you are likely to want RO for tighter control over nutrients.

First, contact you water utility for an analysis. If you are in the USA, this must be provided to you. If the mineral content is acceptable for FO with the addition of marine mix, you have an easy and cheap out. If not, you need RO.
 
RTR said:
If not, you need RO.
Click to expand...

Incorrect.

Rain water, if you have a rainwater tank, the water from their is usually perfectly fine, you just need to test parameters.

Secondly Deionizing units, are sometimes a preffered choice to the RO/DI, there major advantage over the reverse osmosis, is they are 100% water efficient.
 
I am a bit of a newbie to SW fish (I've had a tank for 5 months now), but I do know a bit about water being a chemist. Tap water contains a number of different components besides water - particulates, organic compounds, chlorine (which can exist as slightly harmful to fish chlorine or very toxic chloramine), heavy metals (primarily copper, but also iron), alkali metals such as calcium and magnesium, and anions such as nitrate and phosphate.

Different water systems will remove different contaminants. Sediment filters will remove only particulates. Carbon filters will remove organic compounds and most of the chlorine and chloramine (though possibly not all, depending on their efficiency). RO systems will remove most contaminants, but a small amount of small ions such as heavy metals, nitrate, and phosphate will make it through. The best systems are RO/DI (dionization) systems that remove virtually all contaminants.

Can you use tap water? It depends on a number of factors - what is your tap water quality (especially, does you municipality use chlorine or chloramine), what type of water purification do you have, and what type of tank do you want (FO, or reef?).

In reality, many of us use tap water. I use tap water for my FOWL tank (soon to be reef tank). The water just happens to pass through a RO/DI system before I put it in my tank. If you are considering buying a cheap water purification system from Home Depot, check out RO/DI systems on e-bay. I bought my 6 stage system (brand new) for $100, plus another $100 for 5 years worth of replacement cartidges and DI resin. It reduces total dissolved solids from ~280 ppm to ~4 ppm. To me it is well worth the piece of mind knowing that I don't have to worry about the quality of my tap water (our water has chloramine, which is highly toxic to fish).
 
Getting back to vaderbanger's original question, the difference between the cheapo "tap water filter" from Home Depot and an RO system.

First you must understand that there are many different ways to "purify" water.

1. Charcoal/carbon: most likely the little filters from Home Depot (and Brita filters for that matter) are simply carbon inserts. They are fine at removing chlorine/chloramine/some organics, but virtually everything else gets left in.

2. Mechanical: the simplest way of all, just like your coffee filter. Removes sediment but pretty much nothing else. They also need changing quite frequently.

3. Reverse Osmosis (RO): remember high-school science? It's the natural tendency of water to equalize the concentration of dissolved particles on either side of a membrane. Reverse osmosis uses pressure and a special membrane only big enough for water molecules to force water back to the side with lower osmotic pressure leaving dissolved particles behind. Good RO membranes (such made by Dow Chemical) are expensive and fragile. They usually vary from between 50 - 100 gallons per day. More is not always better as the 50 gpd membrane is more "precise" resulting in less, but better quality water.

RO by itself can't remove everything. That's why RO units (the ones worth buying) are mated up with de-ionization, carbon and mechanical filters to deal with the rest of the "stuff". Those distinctive cylindrical canisters you always see on RO units are actually the mechanical pre-filters. RO also results in quite a bit of waste water as several times more volume of rejected water than RO water is produced.

4. De-ionization: think back to highschool science again. Remember anions and cations? All inorganic impurities like nitrate/phosphate/heavy metals have either a positive or negative charge in water. DI resins bind these ions leaving pure water on the other end. DI resin is expensive and depending on water quality can be exhausted quickly. Also, DI water wants to "take back" the stripped ions and so cannot be left in a metal container. There's a myth that DI water is somehow "bad" for you. It's not, I've drunk it with no ill effects. It just tastes like crap. This is why many RO/DI units have the water pass through the carbon filter last (after the DI filter) to restore some taste to the water.

Which one for you? As stated, it depends on your tap water and what you want to do with it. Here in Vancouver, Canada, we have extremely soft water with a total dissolved solid count (TDS) of 10 - 20. Other places and well water can have TDS of well over 400. The lower your TDS the longer your filters will last (all of them). As a result: know your tap water and a TDS meter is very handy.

If you get a multiple stage unit, the various units should last longer than if they were standing alone. By the way, most of the bottled water you buy is actually your local tap water run through RO/DI.

As far as reefs go - you've got so much invested already, are you going to risk a heavy rainstorm or some kid in the neighbourhood putting a cherry bomb down a toilet dredging up who know's what in the water supply?
 
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