RO/DI questions (1 Viewer)

[Jposch]

Well it's maybe over simplified, but let's just say the mixed bed cartridge is 50/50 anion/cation.

my experience has been that the mixed bed is heavily skewed to cation. If you swperate the resin to regenerate, you'll end up with alot more cation than anion. I did this a few times with mixed bed resin, and same result.
Nor saying its a scam for sure, but in years past, nobody needed to buy add on anion cartridges, and resin tech (the main manufacturer) advertises mixed bed as 50/50. I have not yet regenerated the mixed bed I buy in bulk from AirWaterIce, in original Resin tech bags, but I have a 5 gallon pail full. A large enough sample size, I'd say. Lol
I get about 3,000gallons out of 2 20" mixed bed, and a final 10" mixed bed. I'll be keeping resin seperate after regeneration, just to make regeneration simpler in the future.

But, as I said before, the only thing that gets depleted in my system (at any significant rate) is the anion.

Pretty common for most people.

 

[asifiqbal2]

@Jposch nice! Thanks for sharing

 

[asifiqbal2]

@spsick I was re-reading your post. Pretty impressive. Btw what is your tds before entering the DI stage. I am assuming based on your tank your total water volume is at around 170 to 180 gallons

 

[Jposch]

Another thing, water softener has SIGNIFICANTLY improved filter life for me. The water up hear around saint cloud is very hard. The calcium and magnesium tear up membranes. When the membrane degrades, resin burns faster. A water softener uses cation resin to exchange calcium and magnesium (mainly) ions for sodium ions, which membranes eaaily reject.

 

[Varig]

I wonder if that’s another reason I burn more anion, since the water going into my system is softened. Thoughts?

 

[Jposch]

I wonder if that’s another reason I burn more anion, since the water going into my system is softened. Thoughts?

I had to set mine to regenerate alot more often than default. Silicate will also really cook anion resin. I also have to keep my salt barrel at least half full, or else the water ends up getring hard again.

 

[Bschowa]

Very interesting conversation, does it matter if the anion or cation goes first? If you burn through more anion would it make sense to put that first in series?

 

[Jposch]

Very interesting conversation, does it matter if the anion or cation goes first? If you burn through more anion would it make sense to put that first in series?

I don't believe so. Each removes different ions.
And example: Sodium Chloride (table salt)
Sodium is the Cation, Chloride is the anion. Pretty much everything in water will be a cation|anion bond.
Another thing that burns up Anion resin is co2. This is a big problem for those on well water. The problem isnt that the product rodi will have co2, its that the co2 exhausted thw resin, and now the water will contain other Anion ions which are undesirable, like silicate, or worse.

 

[Varig]

I also have to keep my salt barrel at least half full, or else the water ends up getring hard again.

I’m confused by this. Can you enlighten me please?

 

[Varig]

I’m not sure if order matters or not, but in all my research everyone said to put the cation first. Not sure why, but that’s how I’ve ran mine.

And yes, I’ve also wondered whether the co2 issue is part of why I burn more anion. I’ve debated about setting up a tank for RO water to off gas co2 for a day, then pump it through the DI stages. I’m pretty sure it might save me anion resin. But the way it is I only burn maybe 1 refill a year (since I only have the 65 gallon display and 15 gallon QT tank). I can afford $15/year in resin to not have to jack around with the 3rd big container

 

[asifiqbal2]

I’m confused by this. Can you enlighten me please?

His water Softner bucket so there is always soft water

 

[Jposch]

His water Softner bucket so there is always soft water

This. If I let it get too low, the softener doesn't regenerate properly. The water here is horrendous. I suspect thats why saltwater isn't popular this far north.

 

[Varig]

Oh haha, since we’re talking above making rodi to make saltwater, I was trying to figure out how the water in you’re NSW barrel got hard if it was half full

 

[asifiqbal2]

@Jposch so what is the typical configuration you would recommend, also @spsick how do you have it.
Anion-Cation-Mixed
And basically you never burn the mixed and only Anion… and moreover you burn them at a lesser rate that you would burn a mixed ?

I feel like I have been living under a rock

 

[asifiqbal2]

Also I got marketing suckered into the 200 gallon water saver bla bla in which the 2 x 100 gallon RO membrane are daisy chained. Until I heard Ben say in a reef beef podcast that you are basically burning through more DI…I do make crap ton of water really fast with the booster pump though

 

[Jposch]

Also I got marketing suckered into the 200 gallon water saver bla bla in which the 2 x 100 gallon RO membrane are daisy chained. Until I heard Ben say in a reef beef podcast that you are basically burning through more DI…I do make crap ton of water really fast with the booster pump though

He's right. I talked with airwaterice abour dual membrane options. (Parallel vs series) both have pretty big drawbacks. You are better off just using a higher GPD membrane and possibly upgrading profiler size/micron.
Optimal setup should be tailored to your water. For me, my sediment filter is hardly dirty, and no flow reduction by the time my resin is shot, so I'm going to try a lower micron (finer) sediment filter to see if that makes any difference in resin lifespan.
Before I got a water softener, I had to replace my membrane whenever resin was burned up. Your water may not be as hard due to where the city sources it. My city claims a deep artesian well. Idk about that. It tastes like sewage and smells like bleach. we drink rodi will added minerals, mainly seasalt, some mag and potassium added back. RO bypass is a bit of a crock, as it would only provide 2ppm tds. Basically nothing.
The big thing you want to shoot for is 97%+ rejection rate. Meaning, 300ppm tds tap water is less than 9ppm tds before resin.
The typical sediment, carbon, finer carbon block, membrane setup is fine. From there, you can decide on a single mixed bed, or anion, cation and a final mixed bed. You can add a tds probe after the membrane and between each resin to see whats going on.
Another big thing for me has been to completely isolate my unit between runs and flush membrane for 5 minutes before use.
Shutoff the output, unplug booster pump, shut off incoming water, then drain off pressure from the membrane flush valve and close it again. Tds creep when sitting is a huge deal and was killing resin needlessly. Water is able to permeate past the membrane veey slowly, and bring the ions with it when it sits like that. Ive been told thats very normal, ans shutting it all down like that is best. A bit of a pain, but I make water in 200 gallon batches, and im not big on water changes, so its not like a daily task. Someone with the desire, funds and time could use an apex or even raspberry pi to automate all that with solenoid valves. I use about 50 gallons a week just for topoff.

 

[spsick]

I have 2x 75gpd membranes in series and it’s been working great for me. I replace the first one every 18 months and second one every 12 months. Could probably go longer, I just picked a frequency and went with it.

Most commercial RO units have 2-6 membranes but have a monster carbon tank and boost pump running 175psi.

 

[Jposch]

I have 2x 75gpd membranes in series and it’s been working great for me. I replace the first one every 18 months and second one every 12 months. Could probably go longer, I just picked a frequency and went with it.

Most commercial RO units have 2-6 membranes but have a monster carbon tank and boost pump running 175psi.

Series is good for reducing waste water. Thw second ine scavenges some water from the brine of the second one. Handling higher tds input means shorter lifespan, as you're aware. The only other caveat is that pressure into the second membrane may be lower than optimal.
I don't actually "need" a booster pump, but in the coldest months, incoming tap water can be as low as 34f, and production rate greatly declines, even with boosting the water pressure to 90psi. I used a temperature mixing valve for a while, but it was difficult to keep the temperature within the ideal range. Often being too hot in the summer months, which ruined the membrane. Just wasn't worth the hassle of adjusting it so frequently. If your membrane "telescopes" out. Your setup may need some changes.
18 months from a membrane is pretty short lifespan, but I know i spend at least that much on water softener salt, so not really much savings there.