Dual ro membrane thoughts

[WvAquatics]

I have read through many post and watch all of brs videos on dual membrane. I have 350+tds in my tap so running a dual membrane isn't a great idea. I thought about it and thought of an idea to fix the issue. My rodi came with space saver di housings that I have since upgraded. I thought could I pack one with di resin and run it in between the 2 to membrane. Yes I know the di resin will deplete fast and the membrane would not do anything. But what if I let the di resin go bad and let upto say 200 tds through before changing the resin. Just looking for ideas to double production and lower waste water.

 

[laverda]

I doubt hat would work at all. Once DI gets depleted it will start increasing the TDS in the water coming out of it in my experience.
I have duel membranes and my tap varies from 280 to 400 without any issues.

 

[WvAquatics]

Well that's my thoughts. I would not need the di to remove all of the TDS just enough to save the second ro membrane from having to deal with 400+ tds. So the di could deplete and I wouldn't change until tds got to a point. Idk was just thinking

 

[excell007]

If your plan to connect them in serries, check the TDS coming out of the waste of the first membrane. This may be more than your tap water, since this is more concentrated. A standard 2.5x10 DI cannister can remove approximately 3100ppm, if you put this on the waste line of the membrane, it will exhausted after 10 gallons of 300tds water have passed thru it.

 

[excell007]

if you only want double production and not save water, you can connect them in parallel. You double the production but you also double the waste.

 

[WvAquatics]

If your plan to connect them in serries, check the TDS coming out of the waste of the first membrane. This may be more than your tap water, since this is more concentrated. A standard 2.5x10 DI cannister can remove approximately 3100ppm, if you put this on the waste line of the membrane, it will exhausted after 10 gallons of 300tds water have passed thru it.

Yes I figure it will run out quickly but at what point would the di become useless and allow all 400 tds through. The goal of the small di would be to remove the TDS so the 2nd ro membrane doesn't go out quickly from 400 tds water. I don't see a point in doubling up the waste. I was just trying to figure out how to cut waste down and not burn through ro membrane. It might be more work than it's worth.

 

[excell007]

When it's exhausted it is exhausted, not gradual. We see it at 7-10 TDS when exhausted, this is because that is what the input water is after passing thru the membrane. it is absorbing TDS, when it cannot absorb anymore all input TDS will equal output TDS.

 

[excell007]

I am using dual membrane and my tap water is 320TDS. After about 200 gallons TDS output of the second membrane is still around 8-10. On single membrane configuration I get arround 4-7. You can experiment to see which is more cost effective, but I think burning thru DI is more expensive that burning thru membrane.

 

[Saltees]

The way I see, it comes down to whether water or DI resin costs more. For my case the water costs more, therefore my RO is connected in series.

 

[excell007]

Mine is also in series and the second membrane have at least 200G of filtered water on it and still putting out 8-10 TDS.

 

[WvAquatics]

Thanks for clarifying. I am thinking about using my 150gpd to a spectra pure 200gpd and run the 150 gpd 2nd. With a 200gpd booster pump. All this to make 30g faster until I upgrade lol

 

[excell007]

Here's a snapshot of my storage tank marked with the water I produced in 3 hours with different configuration. I am using a booster with built in flow restrictor, so I have to make a bypass in order to increase the flow of waste water. If I don't do this my waste is less than the filtered water and combine TDS from both membranes is 13. if I keep the ratio at 1:1 combined TDS is 10. I am still figuring out if it is cheaper this way or increase ratio to 1.5:1 to lower TDS to 8. I use waste to water the trees and grass so I am not really wasting it.

 

[WvAquatics]

1.5 to 1 is a good number haha. Yeah I guess I'll just try a second one and see how long the membrane last. Even if I just use a cheaper to membrane for the 2nd one the savings in time is worth the replacement

 

[01xp]

I run a triple romembrane

3 ro membrane

Hey all so I looked and looked but I can't find anything so I'll ask. I have a 3 stage sediment filter going to 2 ro membranes before my so stages. I'm running a booster pump so psi is no problem but I want to get more water with less waste. So I was thinking about putting a 3rd membrane in...

www.reef2reef.com

 

[sunken3]

if you only want double production and not save water, you can connect them in parallel. You double the production but you also double the waste.

from BRS... very enlightning.

 

[WvAquatics]

from BRS... very enlightning.

Yes I watched the video and that's why I thought of a di resin before the 2nd to membrane because I have 350tds.

I run a triple romembrane

3 ro membrane

Hey all so I looked and looked but I can't find anything so I'll ask. I have a 3 stage sediment filter going to 2 ro membranes before my so stages. I'm running a booster pump so psi is no problem but I want to get more water with less waste. So I was thinking about putting a 3rd membrane in...

www.reef2reef.com

3 ro membrane is crazy lol. I don't make that much water. But the waste that low is awesome. So when I replace my filters I'm going to try a 200gpd 1st stage ro. Then run my old 150gpd 2nd. And see how it goes. I want to get good sediment and carbon blocks first and booster pump so water is clean and ro only deals with the tds.

 

[01xp]

Yeah it works great lol water is made fast with almost no waste

 

[laverda]

The difference between my two membranes TDS output is minimal. I do flush them throughly each time I start them. I try to avoid days when the tap TDS is closer to 400 if possible.

 

[Opus]

I think you are worrying too much about this. Unless you have really high tds you are fine. If your tds is under 500 you should get 5 to 7 years out of your ro membrane. My water runs around 400 to 450 and my product water is around 4 usually before the di. Been like that for several years and I expect it to stay like that for a few more.

 

[excell007]

1.5 to 1 is a good number haha. Yeah I guess I'll just try a second one and see how long the membrane last. Even if I just use a cheaper to membrane for the 2nd one the savings in time is worth the replacement

You can reduce waste by reducing the size of the flow restrictor. The downside to reduce waste is a bit lower rejection rate because your're forcing more water to get filtered by the membrane. I used a valve as a second flow restrictor, so I can experiment on the ratio of waste, right now it is at 1:1.