Is My RO Membrane Necessary for 28-30 ppm Source Water?

fishybizzness

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So my source water runs at 25-30 ppm tds. I recently removed my ro membrane due to the large amount of waste water and im still getting 0 tds water after running through my rodi unit. I am currently running the source water through the sediment, carbon and di cartridge. In everyone's opinion, is the ro membrane necessary for such low tds source water?
 

Woodyman

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So my source water runs at 25-30 ppm tds. I recently removed my ro membrane due to the large amount of waste water and im still getting 0 tds water after running through my rodi unit. I am currently running the source water through the sediment, carbon and di cartridge. In everyone's opinion, is the ro membrane necessary for such low tds source water?

Everyone could skip RO and run just DI it's just not typically the most cost effective method of getting down to the "0" TDS range.

No reason you have to run the RO and if your source is that low you won't burn through DI super quick, but I would recommend you add an additional mixed bed DI as a final filter.

If you don't mind the potentially higher operating cost associated with more frequently changing your DI I say continue to skip the RO.
 
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fishybizzness

fishybizzness

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You will be using your DI filter up like 5 times faster. Is the water waste really that much more money then di?
The issue is that i live in the Caribbean and my source water is a cistern that collects rain water off of our roof. This is our only water supply as we don't have city water and i don't like wasting it as it is a really valuable resource. I was just wondering if not running the ro would cause a problem.
 

jeffww

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You could just return the rejected water back to the cistern so it doesn’t go to waste. Tds will creep over time but it will be controlled by fresh rain. Plus, rejected water has been carbon and sediment filtered so its been somewhat cleaned.
 

Uncle99

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RO removes 90-95% of the TDS, the resin is a polisher.
It would completely be up to “what” makes up your source, is that 25ppm good stuff or bad stuff.
 

KStatefan

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I know there are some in the California area that have high water cost and restrictions that are not running a membrane. Jake at reef builders just uses sediment and carbon filters.
 

Woodyman

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You could just return the rejected water back to the cistern so it doesn’t go to waste. Tds will creep over time but it will be controlled by fresh rain. Plus, rejected water has been carbon and sediment filtered so its been somewhat cleaned.

This has my vote for your situation.
 
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fishybizzness

fishybizzness

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You could just return the rejected water back to the cistern so it doesn’t go to waste. Tds will creep over time but it will be controlled by fresh rain. Plus, rejected water has been carbon and sediment filtered so its been somewhat cleaned.
True. The return water is probably cleaner than what was coming out in the first place considering that it goes through my main house filtration before going through the rodi unit. Good point.
 

SDK

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A lot of posts today reminding me of the old days...

You basically just described the Aquarium Pharmaceuticals Tap Water Filter. It was the budget "RODI'" back some years ago. Just an inline cartridge with some carbon, a felt pad and a DI section

If your rainwater is not too bad you should be fine without the membrane if you are getting 0 TDS. I normally always advise to use the full RODI unit, but yours is an exceptional case....

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T-J

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I vote return waste to holding tank. I wish we could do that with our waste on city water!
Well, technically you do. The waste goes to your water company for filtration and then returned to the water supply.

I know that a lot of people collect their wastewater and use it for gardening, clothes washing and other water needs.
 

Eagle_Steve

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So my source water runs at 25-30 ppm tds. I recently removed my ro membrane due to the large amount of waste water and im still getting 0 tds water after running through my rodi unit. I am currently running the source water through the sediment, carbon and di cartridge. In everyone's opinion, is the ro membrane necessary for such low tds source water?
What is your tds after the first bit of filtration. That is where I would measure and determine if I needed to remove the RO membrane.

I would almost bet, with it being rain water where you are, some if not most of the TDS is related to roofing, tree pollen or other things like that. Sediment and carbon would clear most of that out.
 
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fishybizzness

fishybizzness

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What is your tds after the first bit of filtration. That is where I would measure and determine if I needed to remove the RO membrane.

I would almost bet, with it being rain water where you are, some if not most of the TDS is related to roofing, tree pollen or other things like that. Sediment and carbon would clear most of that out.
After my house filtration which is a carbon block and 10 micron sediment it's around 25.
 

Eagle_Steve

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After my house filtration which is a carbon block and 10 micron sediment it's around 25.
Ok, so not what it would be after the ro, but not horrible. Makes me wonder what it would be with a 1 micron sediment and carbon.

I can get my rain water collection in Tennessee down to 7-8 tds from 35-40 with 1 micron sediment and a 1 micron carbon.

But either way, it boils down to how much water you make and how fast you burn through the DI resin. I do not use the RO on one of my water makers, as I call them lol. I use filtered rain water (through 1 micron), then run it through anion cartridge, cation cartridge and then through a mixed bed. I eat up cation resin after about 200-225 gallons, but all I do with this water is to top off my macro grow out tanks. The anion has yet to be replaced in about 1500 gallons and the mixed bed is only there just in case I do not catch the cation being exhausted.

Personally, I would figure out how many gallons it takes to eat up a mixed bed and if it does not hurt my wallet, run with that.
 

a.t.t.r

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Well, technically you do. The waste goes to your water company for filtration and then returned to the water supply.

I know that a lot of people collect their wastewater and use it for gardening, clothes washing and other water needs.
I mean by that logic so does dumping it on the ground lol.
 

outhouse

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I was just wondering if not running the ro would cause a problem.
So I have similar water TDS at 37ppm. I run 3 RO membranes in series and have double the restriction so less waste water. It leaves RO at 0 but i still have it go through 3 stages DI. which literally last years

Remember while my water says 0 every water change will bring on GHA, and it has been like this for 30 years and no shop can find nitrates or phos in the water. Sometimes water just has a chemistry not conducive for our tanks.

I would run 3 or even 5 membranes in series, restrict waste water, then have a storage tank for dishes or showers from this waste water.
 

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