RO Production rates go down in winter

[acroholic]

This is just a general FYI to anyone not familiar with RO production rates as they relate to the temperature of the supply water.

Reverse Osmosis membrane water rates are temperature dependent, meaning the colder the source water, the less RO the membrane will produce, assuming all other factors are the same (water pressure, etc). Source water is much colder in winter vs summer in Atlanta.

So if you have noticed a decrease lately in your RO production rates, it is probably not your RO membrane, or clogged carbon pre/post filters or anything else. When the source water temperature warms up in the spring/summer, the rates will increase.

Some folks warm up their source water to offset the decrease in production. The decrease could also be offset via a booster pump to increase the pressure of the source water going to the RO unit.

I have never done either of these. I just run the RO unit longer.

 

[rjrgroup]

The product is higher purity in colder temperatures as well.

 

[mvm]

rjrgroup;911111 wrote: The product is higher purity in colder temperatures as well.

Isn't zero TDS going to be the same regardless?

 

[rjrgroup]

There is always going to be some smaller particles that aren't measured. Those bypass the membrane more at a colder temperature. There is a lot more in water than dissolved solids. The difference may be minimal but it's certainly worth noting. I use to heat my water until I learned this, now I let it be whatever temp it comes out of the supply.
Edit: you probably aren't getting 0 tds out of your membrane, you should after di though.

 

[giulianom]

I think this thread is Sticky material.

Yes?

 

[rjrgroup]

I would like to convey an explanation of reverse osmosis I recently stumbled across...
Ingested nutrients are dissolved and processed, then enter the blood stream of your body. Those nutrients then travel to all areas of the body where they are "pulled" through your veins to the surrounding tissues where they are needed. The "pulling" is an osmosis process.
Reverse osmosis is the opposite.
The way a membrane works;
Water enters the feed or outer area of the membrane. The pressure builds and begins pushing or squeezing the smaller water molecules through a series of perforated films, imagine a trash bag with millions of tiny wholes wrapped up really tight. The larger particles, contaminants, continue down the surface of the film and exit the waste line. The smaller water molecules eventually make their way through all the wrapped film layers and are collected in the central product or permeate tube and viola, purified water. This is why temperature effects product to waste ratios. They warmer water is less dense and penetrates easier thus allowing more water with attached contaminant molecules through.I hope I haven't confused anyone...?:doh:
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[mikesmith34]

Science is a beautiful thing.

 

[rjrgroup]

Yes it is...except in school...then it's not so beautiful.

 

[buckeye field supply]

Something to consider - get yourself a flow restrictor to use during winter, and a different one to use in summer. Try to keep the ratio of waste water to purified water closet to 4 to 1.

Russ

 

[tmlrfrancis]

Thanks for the info... Didn't know this, but it helps explain why my output is different from day to day as we have the temp. swings! I woke up just the other morning to about 5 gal of RODI water in the basement because the output had sped up! :doh: Typically we produce about 4 gal/hour... I'll watch the weather to see if I may need to 'adjust' my general guideline.

 

[just josh]

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rjrgroup;911121 wrote: There is always going to be some smaller particles that aren't measured. Those bypass the membrane more at a colder temperature. There is a lot more in water than dissolved solids. The difference may be minimal but it's certainly worth noting. I use to heat my water until I learned this, now I let it be whatever temp it comes out of the supply.
Edit: you probably aren't getting 0 tds out of your membrane, you should after di though.

You mean bypass less at colder temps because of constriction?.

ive got a couple r/o units -a srealth 200 and another 67 stage tbat might beed memvranes because if storage.

I was on a houseboat where all of my water was tanked at a steady water temp because it was ambient indoors so I never noticed a change in production

I like the info on this thread it will help me this go round!




Edit: Stealth *200

7 stage*

Sorry I need to turn this auto co-wrong off

Edit: And im learning alot so please forgive me... just trying to wrap my head around the science completely...

 

[hnguyen]

This explains why its taking me almost 1 hour and 20 minutes to get 50 gallons of water instead of my normal hour wait even with my booster pump.


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[smoothound]

I always wondered about that ,why my production would differ for time to time great post.


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[mikesmith34]

just josh;916388 wrote:

You mean bypass less at colder temps because of constriction?.

ive got a couple r/o units -a srealth 200 and another 67 stage tbat might beed memvranes because if storage.

I was on a houseboat where all of my water was tanked at a steady water temp because it was ambient indoors so I never noticed a change in production

I like the info on this thread it will help me this go round!




Edit: Stealth *200

7 stage*

Sorry I need to turn this auto co-wrong off

Edit: And im learning alot so please forgive me... just trying to wrap my head around the science completely...

Actually you will have more bypass due to the increase in water density. Warmer water is less dense so it is easier to permeate the membrane.

 

[just josh]

Ok bypass more WASTE water per gallon clean. Now THAT makes sense. Thank you

 

[michael grady]

I'm glad to see this thread.

I think I may actually have a fouled membrane though. My RODI 6 stage unit is supposed to produce 75 gallons/day. It is producing only about 25 for some reason. When I purchased it and set it up new (about 2 years ago) it was producing nearly 75 gallon/day. How long are these membranes supposed to last?

I have changed all the other elements in my system with no help...

Thanks,

Michael

 

[twhaddon]

I have a question on this as well....

I also had a 75 gpd system and then purchased the 150gpd upgrade. I also get the water from my sink so I can turn it a little on the warm side and it definitely comes through faster.

Question:
Warmer water coming through does not mean that less clean water is getting through, right? I have started to see an issue with my tank and hair algae recently and nitrates going up. wondering if the RODI is less clean now.

Since I upgraded to the 150gpd system I also got a booster pump to help the pressure which now gives around 90psi. But, now my TDS meter reads 0 going in and 0 going out. I am guessing the booster is pushing through so quickly that it can't be read. When I unplug the booster it then reads about 4 going in and 0 out. RODI is less than a year old so I don't think it's the membrane or DI.

 

[michael grady]

Hi Russ,

My water temp is probably around 70 degrees, and it appears my pressure is around 80.

Thanks,

Michael

 

[twhaddon]

Buckeye Hydro;927405 wrote: Membranes often last 2 to 5 years, but depending upon the quality of your feedwater, they can scale/foul in less than a month. What is your water temperature and water pressure?

Russ

Edit:

Warmer feedwater will mean slightly higher TDS in your RO water - but not much. If your RO is near 0, and your DI is 0, you are good to go.

Do you have the probes on your meter rotated correctly?

There's no issue with the booster pump pushing RO water through too quickly for the meter to read.

Russ

My TDS meter is hooked up on the RODI system and I followed directions from the BRS video. I picked up a handheld TDS meter at lunch today and am going to test the water after going through the system with that to see if I get a different reading.

 

[rjrgroup]

TDS meters are highly affected by temperature as well, just thought I would throw another frustration factor out there. Especially our little "Hobby" units.