residential purified water

ionized_gwJuly 23, 2011

How is microbial growth dealt with in residential purified water systems? I am curious about RO and other systems where the residual biocides in the municipal water are removed. How is microbial growth prevented downstream of the residential purifier?

I know that in situations where I have worked, the purified water is recirculated and dead-ends are minimized to prevent problems. Are residential systems so designed?

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In the case of POU RO units there is little in distance and volume from the RO downstream to the dedicated sink faucet and/or water spigot or ice maker in the fridge to be concerned about microbial growth and that water in the line is replaced frequently.

When servicing POU ROs it is vital that sanitary procedures be observed and that the RO be sanitized during these service procedures.

I do not recommend POE carbon filters or softeners with combination media that remove the anti-microbials in municipal water (chlorine, chloramines, and the like) because the entire house is susceptible to microbial growth.

There are softener companies and softener sellers that sell softeners and equipment that does remove the anti-bacterials at POE expounding that the resin in the softener will last longer. I do not recommend doing that. I'd rather replace softener resin every 10 or 15 years than expose people to medical problems that can be costly and very unpleasant and turn into something much more serious.

    Bookmark   July 23, 2011 at 11:48AM
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"How is microbial growth prevented downstream of the residential purifier?"

It isn't. After processing, the water sits in a tank waiting to be used. That's it.

Among providers, there are variations in filtering efficiency of the water before it enters the holding tank. From the holding tank it passes through activated charcoal media and is dispensed to point-of-use....but there is no further anti-microbial treatment.

I am familiar with Kinetico's top-line product, their K5, which has filtering options claiming 99.99% purity. However that water still passes into a holding tank. Their processing limit is 500 gallons before filter-change and that filter-change -- there are four of them required for their purest-of-the-pure option -- also involves a substantial disinfection procedure.

Link is below.

Here is a link that might be useful: Kinetico's anti-microbial option

    Bookmark   July 23, 2011 at 1:48PM
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The K5 has a tandem bio-filter cartridge. The cartridge uses both a bacterial filter (log 7) and a viral filter (log 4). The water passes through the viral filter then into the tank and then into the bacterial filter before being dispensed.

Although the K5 recommends changing filters every 500 gallons, the bio-filtered is certified by NSF/Biovir Labs, to 2000 gallons, or every four filter changes.

Bacterial growth in plumbing is very rare. Well water homes, which have no disinfection or sanitation devices, have no problems unless under some unusual circumstances, such as intrusion from septic systems or leaching from some other contaminated source.

City water applications with--like my own--with whole house carbon filters to remove chlorine provided by municipal water supplies, has no indication wht-so-ever of any bacterial growth after more than ten-years' continuous use. The back of the toilets, the place easiest to see, show no organic growth.

Even so, to sanitized the city water lines, simply remove/by-pass the carbon filter, rinse all household lines and let sit overnight. Presto clean "safe" plumbing. No worries there really.

The was another guy on the net that always went into such extreme rants about how this was some universal tragedy and tried to scare people away from a very standard treatment method that is higher effective and beneficial. Fortunately, we don't see much of him anymore.

Yes, RO tanks can develop organic growth. I have disassembled so many RO tanks to find a very slimy texture to the water bag inside. This is why a carbon block filter always follows the tank water before drinking. I go through staged sanitation procedures before putting RP back into service. Keeping up on filter changes is strongly recommended.

Furthermore, this slimy texture showing organic growth is still very little to worry about as I serious doubt it is anything pathogenic/dangerous (membranes would generally prevent that) but instead may cause some taste and odor issues, that's all. The carbon block is specifically designed to eliminate that problem.

Your question is good and it is important to understand your water and different options in treating it.

Andy Christensen, CWS

    Bookmark   July 23, 2011 at 3:50PM
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Thanks Andy....learned more from you than from the site. I have K5 but don't use the pure/pure option and made assumptions I shouldn't have. Good on ya.

    Bookmark   July 23, 2011 at 4:05PM
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" sanitized the city water lines, simply remove/by-pass the carbon filter, rinse all household lines and let sit overnight"

How does the resin in the softener like that chlorine rinse and bath? Doesn't sanitizing, as you describe the procedure, offset the perceived/advertised advantage of a carbon pre-filter removing chlorine BEFORE it contacts the resin in a softener?

The final stage, carbon block, in an RO is designed to address taste and odor issues and is commonly referred to as a polishing filter. It is not designed to address bacterial issues.

    Bookmark   July 23, 2011 at 5:04PM
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Correction... and apologies to Andy

Andy C did not advocate introducing anything as an anti-bacterial in his rinse instructions but rather just allowing the anti-bacterials in municipal water to run the plumbing system.

Hardly a true sanitizing procedure if colonization has occurred but better than doing nothing and living with the bugs. A true sanitizing procedure would introduce an anti-bacterial (like unscented bleach) at a higher concentration than is found in municipal water and then require a rinse.

Or... not filtering the anti-bacterials in municipal water at POE and living secure in the knowledge that there is no bacteria in your plumbing.

    Bookmark   July 23, 2011 at 5:51PM
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The "Purefecta" filter can be added at a later date by removing the cap/plug that is in place.

    Bookmark   July 23, 2011 at 6:18PM
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All I can say is that I've now lived with the charcoal-first system (charcoal stack before softener) for over a year with zero ill effects for anyone. This location is unoccupied for two-three weeks at a time so that at-risk water is just sitting there in the pipes. We're all healthy and smiling.

Do have K5 RO system for drinking water. That processed water sits in the tank for the same period of time also.

Agree not "ideal" situation but certainly, demonstrably, no problems.

    Bookmark   July 23, 2011 at 10:19PM
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There was a time before municipalities treated water and then it was deemed necessary. There weren't building, plumbing, and electrical codes until they were deemed necessary.

"Agree not "ideal" situation but certainly, demonstrably, no problems"

So far and hardly a scientific sampling. All's well till it's not.

    Bookmark   July 23, 2011 at 10:36PM
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Thanks for the info.

    Bookmark   July 24, 2011 at 1:14PM
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