Water softener and RO/DI?

roostertech · 02/22/2016, 02:07 PM

From what I have been reading it is better for RO/DI to work with softened water?

Initially I was planning to use the waste water from RO/DI to water outdoor plants. But if I use softened water input to RO/DI then the waste would have too much sodium to water plant?

Also I'm getting EcoWater 3502 system, anyone have experience with this series?

Thanks

cloak · 02/22/2016, 02:20 PM

I've always thought that RO/DI basically strips the water of EVERYTHING.. If it's not soft after that then I don't know what is. (7.0?)

Greybeard · 02/22/2016, 02:28 PM

Hard water can shorten RO membrane life. If you have soft water available, it'd be best to use that. Many RO/DI makers sell an in-line softener cartridge for folks with hard water.

In line water softener

roostertech · 02/22/2016, 04:01 PM

Yeah I think similarly to why we run carbon to remove chlorine so it doesn't hit RO membrane.

Would the RO waste water have even higher sodium concentration than the input (softened) water?

sleepydoc · 02/22/2016, 09:23 PM

Water softeners are simply beds of exchange resin that exchange Sodium ions for Calcium & Magnesium ions, so softened water has the same number of ions, just different types. Generally, hardness refers to the amount of dissolved Ca and Mg in the water, so yes, RO/DI water is about as soft as you can get.

RO/DI filters first mechanically filter the water, then chemically filter it with activated carbon. The RO membrane is a semipermeable membrane that uses the permeability combined with pressure to filter most of the remaining contaminants (95-99%, depending on your membrane.) Finally, the DI resin 'soaks up' the remaining ions to get the TDS down to zero.

My understanding is that Ca in hard water tends to form scale on the RO membrane, decreasing it's efficacy and efficiency. The Na+ ions from softened water are less prone to doing so, so using softened water is a good way to improve the life of your RO membrane. you can also use flush systems designed to flush the RO membrane after use and reduce deposits.

The waste water from a RO membrane will have a higher concentration of everything; if it's a 4:1 system (4 gallons of waste for every 1 gallon of RO water produced,) there will be a 25% higher concentration of contaminants in the waste water. If you wouldn't use the water going into the filter for your plants, then you don't want to use the waste water, either.

Note that 'saltless' water softeners do not remove the Ca & Mg, rather they change the ions to a form that doesn't scale. In time this change reverses, so my assumption is that this water would also be bad for RO membranes.

02/22/2016, 02:07 PM	#1
roostertech Registered Member Join Date: Feb 2016 Posts: 148	Water softener and RO/DI? From what I have been reading it is better for RO/DI to work with softened water? Initially I was planning to use the waste water from RO/DI to water outdoor plants. But if I use softened water input to RO/DI then the waste would have too much sodium to water plant? Also I'm getting EcoWater 3502 system, anyone have experience with this series? Thanks

02/22/2016, 09:23 PM	#5
sleepydoc Registered Member Join Date: Oct 2011 Location: Minneapolis, MN Posts: 3,907	Water softeners are simply beds of exchange resin that exchange Sodium ions for Calcium & Magnesium ions, so softened water has the same number of ions, just different types. Generally, hardness refers to the amount of dissolved Ca and Mg in the water, so yes, RO/DI water is about as soft as you can get. RO/DI filters first mechanically filter the water, then chemically filter it with activated carbon. The RO membrane is a semipermeable membrane that uses the permeability combined with pressure to filter most of the remaining contaminants (95-99%, depending on your membrane.) Finally, the DI resin 'soaks up' the remaining ions to get the TDS down to zero. My understanding is that Ca in hard water tends to form scale on the RO membrane, decreasing it's efficacy and efficiency. The Na+ ions from softened water are less prone to doing so, so using softened water is a good way to improve the life of your RO membrane. you can also use flush systems designed to flush the RO membrane after use and reduce deposits. The waste water from a RO membrane will have a higher concentration of everything; if it's a 4:1 system (4 gallons of waste for every 1 gallon of RO water produced,) there will be a 25% higher concentration of contaminants in the waste water. If you wouldn't use the water going into the filter for your plants, then you don't want to use the waste water, either. Note that 'saltless' water softeners do not remove the Ca & Mg, rather they change the ions to a form that doesn't scale. In time this change reverses, so my assumption is that this water would also be bad for RO membranes. __________________ ~~~~~~~~~~~~~~~~~~~~~ 120 gallon, coast to coast overflow w/beananimal overflow. Waveline DC 10000 II return pump, 40 gal sump, Octopus XS200 skimmer, T5 lighting

02/22/2016, 02:20 PM	#2
cloak Moved On Join Date: Jul 2000 Location: Stockton, CA Posts: 14,854	I've always thought that RO/DI basically strips the water of EVERYTHING.. If it's not soft after that then I don't know what is. (7.0?)

02/22/2016, 02:28 PM	#3
Greybeard Registered Member Join Date: Jun 2015 Location: Buffalo, MO Posts: 651	Hard water can shorten RO membrane life. If you have soft water available, it'd be best to use that. Many RO/DI makers sell an in-line softener cartridge for folks with hard water. In line water softener

02/22/2016, 04:01 PM	#4
roostertech Registered Member Join Date: Feb 2016 Posts: 148	Yeah I think similarly to why we run carbon to remove chlorine so it doesn't hit RO membrane. Would the RO waste water have even higher sodium concentration than the input (softened) water?