Why is RODI so much faster when it’s hot?

[Slocke]

Here’s a chart with correction factors, my ground water is approx. 60° F, so their stated factor is about spot on with my real world numbers.

So what unit are you using to get that output?

It’s an AquaticLife 100GPD 4 stage RODI. Very standard.


So put in my meter. I put water is 72.5 Fahrenheit so not hot.
For TDS:
Input water is 60ppm
The product water is 0ppm
The waste water is 104ppm


Based on this I’m guessing it has more to do with the temperature of the filter itself then the water?

 

[Jamie814]

Insane in the membrane

Someone needs to invent a membrane warmer

I use a washing machine box with both hot and cold to mix and run water that is 70-80 which is the most efficient temperature for an RO/DI unit. It also prevents condensation in the summer on the unit. I just have one of those stick-on thermometers on the sediment filter housing to monitor incoming water, but it generally stays the same temp. To hot and you can damage the membrane.

 

[Tamberav]

It’s an AquaticLife 100GPD 4 stage RODI. Very standard.


So put in my meter. I put water is 72.5 Fahrenheit so not hot.
For TDS:
Input water is 60ppm
The product water is 0ppm
The waste water is 104ppm


Based on this I’m guessing it has more to do with the temperature of the filter itself then the water?

cold water has a harder time moving through the tiiiiiiiiiiiiny pours of the membrane.

70ish is ideal temp for making water Enjoy that efficancy!

60 TDS incoming is pretty low as well.

 

[Jamie814]

60 TDS incoming is pretty low as well.

Extremely low! I'm on a 4 year old well and we have around 200 TDS

 

[Solo McReefer]

I use a washing machine box with both hot and cold to mix and run water that is 70-80 which is the most efficient temperature for an RO/DI unit. It also prevents condensation in the summer on the unit. I just have one of those stick-on thermometers on the sediment filter housing to monitor incoming water, but it generally stays the same temp. To hot and you can damage the membrane.

Thank you

I am definitely going to take that idea(s) and implement

Very helpful

Question, is there any impact on the DI resin of running warm water through it? I wouldn't think so, but a day ago I didn't know I can halve the time with warm water through the RO either

 

[Randy Holmes-Farley]

Thank you

I am definitely going to take that idea(s) and implement

Very helpful

Question, is there any impact on the DI resin of running warm water through it? I wouldn't think so, but a day ago I didn't know I can halve the time with warm water through the RO either

Water temp won’t impact the di, but too warm of water is not good for the membrane.

 

[Solo McReefer]

Extremely low! I'm on a 4 year old well and we have around 200 TDS

My city water is at that

I'll bet your TDS tastes better than my TDS

I have been on well back in the past, much better

 

[ryshark]

It’s the increased viscosity of the water at lower temps that slow it down and its a dramatic change.

This makes sense, because my pressure coming from the house is the same year round.

 

[Extremeengineer]

I guess I'm weird, but I set the temperature before I make water.

I wouldn't say weird, but my RODI feeds off a saddle valve on a cold water line, so I don't have that option. I imagine my setup is not very unusual. I could plumb both hot and cold over near the unit and put individual valves or I think I even have one of the spare Kohler mixing valves from our showers that keeps a constant temp, but it just doesn't seem worth it. That's not to say I wouldn't like reducing my water making time, but I keep hearing patience is the key to reefing lol

 

[Northern Flicker]

I feel like I remember my Spectrapure unit's manual saying something like "lukewarm water at 70psi is ideal" or something along those lines.

 

[BeanAnimal]

I think heating the water to reduce waste likely costs far more than the otherwise waste....

 

[Dorsetsteve]

On the Chalk Seam in the U.K. here, incoming water is in excess of 350ppm. You have to squeegee your shower screen or it will be covered in white marks when it drys.

 

[teleportinghere]

I think heating the water to reduce waste likely costs far more than the otherwise waste....

There is truth to this for sure, especially for larger tanks. It also may introduce more water heater contaminants that the filter now has to process, thus requiring more frequent replacement of certain cartridges.

On the other hand, it's much less waste water when I do a temperature check beforehand. I use my reject water for the garden and end up storing much less of it when the temperature is in the efficiency zone.

 

[Tamberav]

The hot water here TDS is higher than cold so that’s something to consider if it’s even worth using to bring the water temp up.

 

[Randy Holmes-Farley]

There is truth to this for sure, especially for larger tanks. It also may introduce more water heater contaminants that the filter now has to process, thus requiring more frequent replacement of certain cartridges.

On the other hand, it's much less waste water when I do a temperature check beforehand. I use my reject water for the garden and end up storing much less of it when the temperature is in the efficiency zone.

TDS also gets through ro membranes more at higher temps. You may reduce waste water at the expense of faster di depletion.

 

[Slocke]

I thought I heard that hot water has higher TDS and thus why you should always cook with cold water.

 

[Randy Holmes-Farley]

I thought I heard that hot water has higher TDS and thus why you should always cook with cold water.

Aside from more dissolution of your pipes, I don’t see how the actual tds rises much between a hot water heater and your tap. But for cooking, not drinking the copper or lead that did dissolve would be desirable.

 

[GARRIGA]

Flow rates are quoted at 77F. Use the multiplier below to determine approx flow at other temps

Perhaps hook it up to the hot water heater then

Was actually thinking about doing that when I just installed a new water heater. Plumber saw no issue with although didn't mention I'd want it off the hot water. No clue. I'm not a plumber.

 

[Randy Holmes-Farley]

Perhaps hook it up to the hot water heater then

Was actually thinking about doing that when I just installed a new water heater. Plumber saw no issue with although didn't mention I'd want it off the hot water. No clue. I'm not a plumber.

Lastly, it is not recommended that you introduce water from your water heater in an effort to increase water temperature. RO membranes cannot handle water temperatures over 100 degrees F, and all water heaters have silt and other sediment in their reservoirs that can damage the membrane and RO unit.

How Temperature Affects RO Water Production

Every year, thousands of dollars are wasted on unneeded membrane replacements because hobbyists overlook the negative effects of cold water on their reverse osmosis (RO) system performance. Assumptions are generally made that their membranes have fouled, when in fact the temperature of the feed...

aquaticlife.com

 

[Jamie814]

I think heating the water to reduce waste likely costs far more than the otherwise waste....

This is true, my main reason was to prevent the condensation on the unit in the summer which over time rusts the metal screws and bracket of the unit and drips on the floor.

I'm not running hot water through the unit only mixing to get water in the 70-80F range.