Can I run softened water through RO?

[olegren]

I feel like this is a dumb question, but I'd like to make sure I understand correctly.

Background: I have well water. It's hard (260-400ppm depending on rainfall), so we have a softener that uses salt pellets. Up until recently, I was watering my plants with the hard water. I bypassed the softener because I've read a lot about how detrimental those salts can be to plants. I'm still worried that there are too many unknowns in my hard water though, so I am considering an RO system.

My question is: Is it safe to use water that has passed through the water softener and an RO system? Or would I need to find a way to install the RO system ahead of the softener?

I have read that softened water can help protect an RO system, but I want to be sure the RO process would remove anything potentially harmful to my plants from the softened water.

Thanks in advance for your insights!

 

[Green Hornet]

No Bro I would avoid watering plants with softened water. Yes you can run it through a RO system and then use for plants.

 

[olegren]

No Bro I would avoid watering plants with softened water. Yes you can run it through a RO system and then use for plants.

@Green Hornet Thanks for the reply! My intent would be to do this:

Softener -> RO -> Plants

In other words: Does RO remove whatever the softener adds that might be detrimental to plants?

My reading suggests that RO removes most of the salt anyway. Just curious if anyone has run into it.

 

[Green Hornet]

Yes and protects entry piping and components. Any sediment filters before the RO system is another plus

 

[olegren]

Thanks!

 

[Waira]

... the softener is mainly only removing the CaCO3 hardness through ion exchange process. In water, to various degrees, CaCO3 dissolves into Ca++ and CO3-- ..... The free Ca++ in the water has strong affinity for resin beads, so they preferentially bind (adhere) to the surface of those beads, but to do so the Ca++ molecule displaces the salt ion stuck to them (Na+ or K+ typically) because of it's stronger charge,...When all the bead surface area is choked up with Ca++, then the water won't soften anymore and needs to be stripped off by a very strong salt solution. This soln. forces the exchange equation (if you will) the other direction, knocking off the bound Ca++ through sheer concentration, rebinding the K+/Na+ to the surface and thus "recharging" the beads....
RO uses a literally molecule sized perforations on that film filter to strain out nearly everything; H2O is smaller than K and Na, not by much though! Some smaller ions can get through in small amounts, but this is why you test your RO water with a TDS/EC meter...
Anyway, the RO system will work better with softened water going through it vs. the raw well water... On occasion you have to back flush the RO membrane to strip crap off it and restore some filtering ability, which makes it last longer,... Certainly a particulate prefilter (5-10micron size) and a Carbon filter (pulls some nasty organic/chemical molecules, heavy metals out) will do even better. most small systems for say, aquariums will have 3-stage filtering like this... The more you get the crap out of the water before RO stage, the better it will last and perform,... Particulate is especially important since the water may be loaded with micro/nano bits and crap that clog things up very quickly !
HydroLogic is a fine company, they have a couple small volume models, but shop around on the net and see.... I have an old Coralife Pur-flo II that basically not made anymore, parts tough to get or are not made anymore forcing me to monkey around with things to keep it going,... filter casings tend to blow out eventually too, a big negative so next time I'm chucking the system and getting something newer....

 

[olegren]

Damn, @Waira , you know everything! Suffice to say Chemistry was not my subject in university. :smoking:

Thanks for the detailed explanation. This is kind of what I was assuming. Given that RO is supposed to strip damn near everything, I would expect that nothing residual from the softening process would really be left behind; or at least not to the extent enough to harm the plants. I actually got here based on your feedback in the Prescription Blend thread.

The more I think on it, the more I am confident that my hard water is at least partially responsible for my stunting/nute issues. My smart pot had some gnarly white calcification splotches on the outside; which is the same thing we see on fixtures when our salt is running low or the beads need a recharge. At least with RO I will know exactly what is going in and can calibrate accordingly.

I have been shopping systems off and on for a few months but only recently getting serious about it. Seems like many of these aquarium rigs are more portable; which I like a lot. I had come to terms with installing something under the sink but would much rather have something I can set up at the faucet to fill jugs weekly or thereabouts. Thanks again for sharing your wisdom!

 

[Waira]

I looked at HydrLogic's site, and saw 2 options: the MicRO75, which doesn't have the sediment filter built in (do you have a whole-house sediment filter set up already? With well water, it's generally advisable), and the Stealth 150 (GPD), which does,... There are cheaper units, but they aren't fitted with the better parts, and don't come with Flush kits... 150gpd is kinda overkill, but the plus is the filters will last longer...
Saw this on Amazon-

...point is to avoid the cheapie units, seems there's a lot of issues so a little more investment might be better value in the end... Also, there's no need for a 4-stage unit, that last stage is a rather redundant deionizer stage, so don't bother on this... sediment, carbon, RO membrane = 3 stage, plenty good!

 

[olegren]

I was looking at that very unit earlier today. When I was looking for basic RO systems, I was finding a lot of under-the-sink rigs. To that one's name's credit it does sound a lot stealthier than several. Being able to hook up to a garden hose or faucet, git 'er done, and then stash it someplace is a huge plus for me. The way above-average GPD makes the effort around manually cranking out some water a little less intrusive. A tank seems like a lot of cost for very little benefit.

I have seen the flush feature on a few but didn't realize it added on to the life of the units so much - Thank you for that!

 

[BII]

Have you considered collecting and using rainwater, melted snow, air conditioner/dehumidifier condensate etc.? And if you feel a need, have a basic RO unit for backup? Water vapor condensate is essentially 'pure' water and has negligible amounts of salts/ppm, probably similar to RO water. It's also free and avoids disposal of lots of concentrated salt solution, dealing with filters and plumbing and other downsides with RO units.