Using water softened water into my RO/DI


New member
As in "water-softener" softened water...

I don't think used softened water will hurt the RO/DI or negatively impact the output... but asking just in case I'm missing something.

On an aside, I also think it's perverse to remove heavy minerals like calcium, replace it with sodium, then go through an RO/DI, then add salt and finally work on keeping my dissolved calcium as high as possible.


-RT * ln(k)
The worst thing that water softener will do to your RODI is make the filters last a bit longer. :) Other than that it really won't make much of a difference.

rick rottet

reefkeeper// propagator
agreed. RO membranes, carbon blocks, and prefilters can better deal with more soluble particles such as sodium then it can with things like iron. air/water/ice, for one, recommends softeners.
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New member
Culligan and The filter guyz both told me that the RO membranes will last 5-7 years with softened water going to my RO units (2 of them, one for drinking - culligan, and 1 for the aquarium - The filter guyz).

They told me if I don't soften the water before going to the RO membrane. The membrane would last at most 1-3 years if I'm lucky. However, my city water TDS tested out at over 1000 according to my tester and to Culligan's tester... If the non-softened water TDS were 200-300 vs. 1000 then, I suspect the RO membranes would last much longer without being softened.

So, in short, it's better to use softened water. If your city water supply TDS is really low, it probably would have a huge impact. For me, it will double my RO membranes' lifespans.