RO cost-effective, compared to well/ tap water?

[Yossarian88]

I had read through threads to try to get an answer, but I'm still a bit puzzled on the conventional wisdom of using RO versus tap or well water. Please bear with me as I get tedious.

 

Based on my City's 2010 "Water Quality Annual Report," the highest reported total inorganic nitrogen (adding NO2 and NO3) concentration was .065 mg/l. (The highest reported value for NO2 was .01 mg/l, so no serious worries there). Compare that with a 75 gallon tank running at 10 mg/l total nitrogen -- not ideal, but workable and realistic. (Right?) Consider either mass or concentration.

 

From a mass standpoint, to simplify things, the bacteria in the tank are constantly treating 750 mg of total nitrogen, coming from the living things in the tank. If the tank were originally filled with my City's tap water, the mass contributed from the tap water is 18.47 mg. What's the fuss about that additional mass of TN from the tap water?

 

Second, from a concentration standpoint, even in a well-run system, is .065 mg/l really something to be concerned about? From my understanding, you get to 3 mg/l TN in advanced municipal wastewater treatment. Also, from my quick review, at least in a fresh water system, .065 mg/l would be pretty low, substantially lower than the vast majority of Florida freshwater systems. (Granted, I don't know what concentrations would be like in a natural reef system). If water changes are to be done, unless you are much less than 10 mg/l, I gather that you could offset the added TN mass in the water change simply by doing a slightly higher volume in the change.

 

Finally, to add an additional twist -- I use well water, which means I would not have to worry about chlorination, and I am taking a guess that my ground water would be no worse than the City's, which is also from the Floridan Aquifer. I am guessing, but do not know, that the calcium in my well water would be a good thing.

 

From this, it looks like I would have diminishing returns from using RO. Have I missed something or should I really use RO?

[kory]

Ro/ Di u need purewater or you will get extra stuff u don't want. Dumb downed version

[GiantBen]

Ro/ Di u need purewater or you will get extra stuff u don't want. Dumb downed version

This reply is fairly useless.

[Austin]

Well HOWDY YALL, the consensus around these parts (which I tend to agree with) is that a TDS of or very near 0 is the ultimate goal regarding water quality. So, if you have access to (or are willing to purchase) a TDS meter, I think you could test your well water, determine its value, and presto-changeo you've got your answer!

 

There MAY BE factors other than TDS that determine a water source's useability - and there are many expert water wizards on this board that can verify for you - but I'd say TDS is a good starting point to determine if YOUR water is acceptable for your tank.

 

Peace be with you and also with you

[fewskillz]

Some people have used tap water with good results. Those people 1.) were very lucky, 2.) tested the crap out of their water beforehand.

 

Austin is right. It's about TDS (total dissolved solids), not nitrogen. It's also about consistency. Our reefs need stability. Only RO water is going to be pure every time. Water from the city, or your well, will fluctuate. Even if you use it, you still need to treat it with something. Those treatments cost money and will add up to a significant value over time.

 

At a minimum I recommend buying RO water from your LFS. What I really recommend is do yourself a favor and spend $200 upfront on a decent RO unit and a storage container. It took me 3+ years to pull that trigger and I haven't looked back. I also haven't taken a bucket to the LFS in months, that is a nice change.

[blasterman]

As I understand it free nitrogen tested in municipal water supplies is a bit different than nitrogen/nitrate we test for in aquariums. The former has already gone through a biological cycle at the filtration plant and is 'supposedly' not quite as rapidly utilized by nuisance algaes, etc. At least...that's the theory.

 

My opinion is that nitrate levels below 1ppm aren't much to worry about. However, it's phosphates, silicates, metals and other things that cause more problems.

[AZDesertRat]

Nitrates is probably not a good example as they are easily dealt with by the bacteria in a reef system and are not cumulative like many other contaminants.

 

The biggest problem with tap water is inconsistencey, its never the same, day to day or even hour to hour. Most municipalities have multiple sources be it deep wells, streams, rivers, lakes, reservoirs, impoundments, canals..whatever.

Sources change just as demands change so what you have today may be different tomorrow. Add an additional well or surface water source and treatment changes. The pH goes down so thye begin adding orthophosphates or polyphosphates to control corrosion in the distribution system. Chlorine dissipates at the ends of the distribution system so they switch to chlorine dioxide or chloramines. A storm blows through and stirs things up so they add more chemicals and coagulants/filter aids to assist with particulate removal.

 

Joe Contractor hits a fire hydrant down the street while he is instaling a new sewer service. Big problem. The industrial plant on the edge of town has a bad backflow preventer and gallons of process water get sucked back in to the mains. Your neighbor left his garden hose in the treewell after fertilizing his trees and that gets sucked in when the hydrant gets hit and causes a backflow. The cooling tower down at the local shopping mall sends pressurized cooling water back into the mains.

 

The list goes on and on and all of these things happen daily.

 

The point is you have zero control over tap water even if it left the treatment plant in pristine condition. You might test for nitrates 10 minutes from now and they are low but what about the benzene from the industrial plant or the leaking gas station tank on that vacant property? Or the phosphates they added this morning when the pH dropped?

 

With RO and especially RO/DI you get consistency, even moreso if you own and maintain the RO/DI system yourself. I would never ever, did I say never, use tap water in a reef system no matter where I am located or what the source. You get too much invested and we as reef hobbyists should be serious about the inhabitants we are keeping. If I did not think I could keep a anemone, coral or fish for its entire lifespan I would not be in this hobby. I for one take it seriously so choose to provide the best care I possibly can.

 

You must also consider the annual Consumer Confidence Report or what many call a water quality report is only a snapshot in time. The EPA says utilities must list all those things tested for in that calendar year, along with the ranges and MCL's. One problem is not all constituents must be tested each year, some things are still on 3 or 4 year cycles so will not be listed but every 3 or 4 years. That could be too late for your reef. Another problem is the test results are what was found at that given moment in time, it can and will change according to weather, demands and usage, changes in the river flows and runoff, many things have an effect on water quality. Most things are also tested at the source or "Point of Entry" to the distribution system. This does not account for water quality degredation in the distribution system.

 

In your case with a domestic well, do you or have you ever had even the basic "well suite" tests performed by a certified lab? You should do this at leas tevery couple of years, especially if the well is several years old or older. Conditions change. You could be influenced by a near by septic tank or leach field, or herbicides and pesticides. Minerals are often very high in deep wells and iron and manganese can be problems in shallower wells. You could have sulfate reducing bacteria or iron eating bacterias and not even know it.

 

A basic well scan is less than $200 at most labs and well worth the time and money.

[Yossarian88]

Thanks to each of you for the responses, which has made me think about this some more from different angles. I had been focused pretty much on nitrogen, and Blasterman had a good point about "other things." But, the examples you provide -- phosphate, silicate, metals -- still leave me wondering what "other thing" in the ground water is (a) going to be in higher concentration than the tank water and ( worth worrying about, compared to concentrations in the tank. Phosphate, good question -- might want to check my well water, I suspect it will be relatively low, and I am failry confident that is easier to treat than nitrates. Silicate, I don't have any information in the background, but I am suspecting that what is in the tank is higher than my drinking water. Metals, even better question, especially if there might be copper or lead lurking in my ground water. Whatever metals are in my water have not killed me yet, but that is not a complete answer either.

 

The point on consistency is also a good point, and I am still thinking on that. I wonder if the changes in background would be significant in comparison to everything else is going on in the tank.

 

By the same token, high total dissolved solids could be related to problems, but would not answer that question. The question is, what is the dissolved solid that is the problem? (Illustration: the TDS in your tank is going to be way higher than tap water strictly from the added salt and dissolved calcium). The question is, is there reliable information that some solid is likely to be in a concentration that would be a problem?

 

I am mostly curious because of horror stories about flooding that happens when people forget what they are doing with their RO units. I have wood floors on the first floor, and I can picture bad things happening after a few martinis. I have been buying jugs of Walmart RO water for my Aquapod, and I can see that would be a PITA when I finally get my 75 gallon tank going. I did not have any serious problems when I used well water for a fish-only tank, but that also is not a complete answer.

 

And, well, it's good to ask questions about conventional wisdom.

 

Again, thank you very much.

[Yossarian88]

AZDesertRat, thanks as well. I did have the well tested about ten years ago; because of local land use, I have not been too concerned about anthropogenic sources. But, a test would be cheaper than an RO unit, so I should at least have that done before going with well water. Leaving the disturbing question: you test the water for your tank, but don't worry about it for yourself?

[AZDesertRat]

6 years ago I moved my RO/DI out to the garage after flooding the wifes kitchen a few times when I forgot to shut the water off while filling buckets or jugs.

Now in the garage I have an autotopoff storage reservoir made out of a 23 gallon Rubbermaid can and float switches. It has not failed even once. It feeds in to the house via a 1/4" line pulled by a peristaltic pump which maintains my sump level and again is controlled by a liquid level system using switches and even a back up high level switch. Bulletproof and no labor involved.

 

 

I would much rather start out with true 0 TDS or 18.2 megaohm resistivity RO/DI water and add only the necessary elements in the form of a reputable synthetic salt mix. I have used IO, Reef Crystals, Red Sea, Ocean Pure and Oceanic and had no problems with any of them when mixed with RO/DI. The TDS of fresh new saltwater is going to be somewhere over 32,000 ppm so a TDS meter won't tell you anything since they are limited to levels much below that. The nice thing is since I am not adding any cumulative metals or elements with my water I don't have to worry about them accumulating over time. With tap water no amount of water changes will vere remove all traces of certain things.

 

We drink RO water at home. The RO is hooked to the kitchen sink, laundry sink, ice maker, pet watering and refrigerator door water and icemaker. I love the clear ice cubes and lack of floaties!

 

I have done many spreadsheets and calculations on water costs and my RO/DI costs less than $0.05 a gallon including the water and sewer rates and tariffs and replacement filters and DI resin. RO is cheaper than that since it does not include resin. Even if I were to add the cost of the RO/DI unit and depreciate it out over time its still less than a dime a gallon.

[DaJMasta]

With proper shutoffs and care an RO unit will not be dangerous to your wood floors. At least no more dangerous than a 75G tank would be.

 

 

In my mind it comes down to this:

RO/DI water has a TDS of 0. That's less than 1 mg of extra material per liter of water (provided you can't measure gradations lower than mg/L-ppm).

Tap water ranges from a TDS of maybe 50 to well over 1500ppm. That means in the BEST case scenario, you will have 50 MG of extra crap per liter of water in your aquarium. That comes to more than 15 grams of stuff you don't know about going into an initial fill of a 75G aquarium. This includes heavy metals, organic compounds we strive to get rid of, chlorine or chloramine, etc. If you use something to treat the water and neutralize some of the bad stuff, you are adding probably more than a quarter gram per liter of extra stuff in your water that you don't want to be there, though it will make things somewhat less toxic. That gets you to 90g of extra material in your tank.

 

So that option doesn't seem so good, but here's where it really gets bad:

Now consider evaporation and topping off of that 75G aquarium. Let's say it looses 5G per week to the air (a number I pulled out of my ass). That means by using treated tap water as your top off, you're adding 1.5g of extra material to your tank every week - and this is assuming the 50ppm TDS that is realistically the BEST you can hope for for tap water quality. Considering how little phosphates or silicates it takes to get an algal or diatom bloom, this could very easily mean the difference between a bright green tank and a coralline covered tank. There's also no telling what the extra stuff in the water is or how it will affect your livestock. The only way at this point to keep the ATO from continuously raising your nutrient levels is to do more water changes, but while they will help it will continue to build up at a slower rate.

 

 

In a situation like a reef where water quality means so much, spend the $100-200 it will be to get even a base line RODI system and keep your livestock healthier and your glass cleaner.

 

On a related note, I started my first reef tank on tap water because of the RODI expense and difficulty of installation in an apartment. When I switched a couple months in my GHA problem was dramatically reduced and film algae growth went along with it - in no more than a couple of days the difference was obvious. My tap water had a TDS of 165 and was being treated to neutralize heavy metals, I would get a film algae bloom after every water change on tap water.

[blasterman]

My local reef shop has some incredible show tanks over-grown with insane SPS they can't frag fast enough. They use straight city water - no filtration.

 

They base this on water tests that prove the municipal water supply is very, very clean. My water (I get my water from a different township) has enough TDS to qualify as a milk shake.

 

The problem with the reef shop is every now and then they get a spike of something in the water they have no control of, and over night they'll develop green slime growing over a prized acropora, and I'll stop in and laugh.

 

Odd that some people like the taste of RO water. Can't stand it myself (give me those extra tasty ingredients of city water).

[ajmckay]

I think one of the main points that has been on my mind as save for a good RO/DI is the issue of water consistency. While the water supply has inconsistencies, remember also that each reef tank is different and just because person A uses tap in his tank just fine doesn't mean person B, with the same water supply, is going to have the same outcome and vice-versa.