The wcr guide to pure water cleaning recommends DI only as being more cost-efficient if your TDS is under 100. When i look at this chart on resin life, it leads me to a question:
https://windowcleaner.com/waterfed-poles/understanding/purification/
According to the chart having an RO system lengthens the lifespan of the resin by 12x if your TDS is around 50. Since replacing the resin costs about $200, that means DI only would cost $2400 in the same span of time that RO/DI would cost just $200 (and of course $400 for the RO every few years). This is giving me the impression that RO/DI is cheaper in the long run regardless of how low your TDS. Is there something I’m not seeing?
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Good question.
I’ve experimented over the years to figure out the best possible setup for myself.
Our tds varies from 90 to 130.
For 1 entire year (2015) we used RO only which means 002-012 ppm. We saved maybe $500-$750 in di resin. Plus, time savings. However, we noticed a difference in cleaning ability. The RO only water doesn’t quite have the same cleaning power as di.
All last year we went back to RO/DI and really enjoyed the increased cleaning power of di and the trust factor of knowing you’re working with pure water.
Recently, this Spring, we’re experimenting with DI only in order to possibly lighten the load of our cargo bikes. Even at 090 ppm coming into a dual di at just enough trickle to offer effective flow at the brush we burn through it in a day. It may be the fact that our city’s pipes are literally from as far back as the 1880’s or just simply that di only is good for short jobs and/or 050 ppm and less. It may lighten the load for our cargo bikes but it’s not nearly as cost effective as RO/DI.
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With a RODI the resin amount is very small. The Zero Pure has the largest tank at 1/4 cubic feet. So the numbers are based off taking this into consideration. Also DI is made up of about 60/40 mix of caton and Anon beeds. Some areas have minerals that will expire one or the other faster. Most of the time in the old DI tanks all the resin is not getting used up before the readings climb high. That is why Unger designed the pressure plates and shower like water flow in the Hydropower to make sure you get full use of all your resin.
They claim 30% more life but that has not been proven to me yet.
Remember we are dealing with WC all over the US with TDS levels ranging from 0 in SC to 900 in AZ. So that is how we came up with the benchmark of 100 PPM
Hope this helps you
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I did some more research and found that some areas in my service range have a TDS over 100, so I might just get the complete system to be on the safe side.
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With the Xero you always have the option to run RO only, DI only, or both together.
There are a multitude of situations where one configuration might be better than another. Best just to cover all your bases, IMO.
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A lot also has to do with your budget . I would rather get a top of the line pole and just go with DI, than getting a RO/DI and a cheap pole .
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The packages we have now with the Xero Pure and a pole are very reasonable. I would go with the Pro version.
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