Reverse Osmosis & Deionization

[AquaFX]

DI Resin

Ken,

You can use any type of filter that will provide the water full contact with the resin.

For instance; in a tradtional filter housing the in and the out are at the top. This way all the water has to travel the entire length of the resin column to exit.

If you like the idea of a distrubution tube, I suggest feeding the water at the bottom of the DI coulmn and letting it rise to the top. Use gravity to your advantage.

Let me know if this helps. Color changing DI resin is also a nice feature, providing you a "heads up" to the exhaustion rate.

Marianne
www.aquafx.net

 

[AquaFX]

Wow, great thread!!!

In the past, when I would start up my RO/DI unit, I would waste the water for the first 5 minutes or so before putting the output in my trashcan. It is my understanding that when you first start up your unit, that water will be dirty.

Is this a good idea or is it wasteful?

You are correct

TDS creep is natural. When you stop "reversing" osmosis (or applying pressure to the feed water side of the membrane) OSMOSIS happens. Even when you are applying pressure, osmosis is still present, the higher the TDS the higher natural osmonic pressure is. That is why you need approx 600 PSI to purify sea water. This is the nature of membranes.

A permeate pump helps stop this.

I use the example of turning off the engines in an airplane. When we stop over coming gravity, the natural forces take back over. The larger the mass the larger the force acting on it.

Marianne
www.aquafx.net

 

[AquaFX]

Someone else asked about letting the unit sit for a while NOT being used. Mine sits soemtimes for 2 weeks without any use. Does that have any effect on the filters or membrane. Lastly what is the approx lifespan of the membrane itself (sorry if I missed that somewhere) and do the membrane flush kits really help prolong the life of the membrane??

Thanks Scott

Scott,

As soon as the water passes through the carbon, there is no more residual disinfection. This means there is a potential for undesirable baterial growth. Now the water is purified, and the membrane can deal with A LOT. Again the TFC membranes are bacteria resistant (just not chlorine resistant)

The biggest danger is in the membrane drying out, this will kill a membrane. I recommend putting the unit in a plastic bag, like a contractor bag. This way no light can get to it and it will be kept moist.

periodic disinfection of the entire unit is also recommend. If you ever smell a foul odor DISINFECT right away.

Truth be told, there a very few problems. DO keep the unit wet!

Marianne
www.aquafx.net

 

[Slickdonkey]

Is anyone familiar with these units? I was thinking about getting one. Currently I only have an RO unit but am thinking of moving to fancier corals one of these days.

 

[AquaFX]

3 things affecting efficiency of an RO

Got crazy busy sorry it took me so long to get back

The 3 things that will dictate how well your system operates are pressure. temperature and water quality.

1. Pressure; Most membranes can handle hundreds of pounds of pressure, and the more pressure, the more efficiently the membranes operate. The limitations are on the other components of your systems, which will NOT handle hundreds of pounds of pressure. Most systems should not have anything over 80 PSIG. Osmosis is a natural process (like gravity) for our purposes it must be overcome. It is generally accepted the 35 PSI is the minimum amount of pressure needed to produce a permeate stream through a membrane. If you get a chance to vary the pressure of your system, I believe, you will be amazed at the output variations. With higher pressure the water quality will improve and you will see the waste stream volume will decrease. This is the easiest of the 3 to safely control.

2. Temperature; tricky (in a word) 80 degrees F is the optimum temp to operate your RO membrane. The problem is, much higher and your membrane is toast . So if you want to increase the water temp, BE CAREFUL!

3. Water Quality; The incoming TDS is normally made up of calcium salts. If you have access to soft water USE IT! Almost every commercial RO system in the World is feed with softened water, Calcium scales, Salt (NaCl)dissolves. Your membrane will thank you! Not only will it extend the life of your membranes, but your permeate TDS will be lower. It is much easier for a membrane to reject salt than it is for it to reject calcium.


Therefore, use a booster pump under 35 PSI (or if you can afford a booster pump add one for any pressure under 55 psi, you WILL SEE AN immediate benefit) Warm you water EVER SO SLIGHTLY and use a water softener.

I know, tall orders. But if you are having trouble, you maybe able to correct the one area that is giving you problems.

Marianne
www.aquafx.net

 

[AquaFX]

Meters and Gauges

This is a good next topic, because it ties in with the one before it.

You NEED a pressure gauge, now the word need is subjective, but I believe you NEED to gauge the pressure of your system.

First it lets you know your system pressure when all the prefilters are new (optimum operating pressure for your location) and as your gauge pressure drops you know the sediment filter is clogging. {this is assuming your gauge is after your pre filter set} If it is not, add one or move the one you have. A sediment filter is cheap, and because pressure is SO important to the RO process, change it as soon as you see the pressure dropping.

The first question I ask, if someone is having trouble, is "what is your pressure?" If you can not answer that question.................... I am just guessing on how to help.

You do see gauges on most of the better systems.


I also believe a TDS meter is needed. I already talked about membranes, but they too are made by humans. Some are not as good as others and some membranes fail. You will not know if your membrane is any good without testing it. People ask, how do I know when to change my membrane, and a TDS measurement is the ONLY way to know. Now you can tell if you start burning through DI filters, that something is wrong, But that will cost you more than a meter.

Marianne
www.aquafx.net

 

[AquaFX]

Feed Back Please!

Let me know what else you would like, or I promise you, I will just keep ranting :lol: :shock: :doubt: :eek2:

Marianne
www.aquafx.net

 

[NaH2O]

Marianne - I'm not sure if I asked this yet, but when you see a unit for sale and it says 60 gpd or 100 gpd, is that assuming ideal conditions like pressure, temperature, TDS?

On inline TDS meters, I've seen this asked before, is there ever a need to calibrate them?

Does something like the RO Water Buddy help with the temperature issue?

 

[AquaFX]

Gpd

That is true with most membranes. I believe everyone but DOW rates @ 60 PSI. DOW rates theirs @ 40PSI.

TDS is around 120ppm, (again with DOW) Not sure with others.

I do know that DOW is very conservative and you Normally get the projected flow rates.


NOT A PLUG but you get what you pay for (when your lucky:eek2: )

TDS meter (most of them) have a calibration screw somewhere, but very seldom need calibration. I say "if you drop it off the roof, calibrate it". Trick=brand new DI, trickle water through it, calibrate to zero. PLEASE USE ONLY QUALITY DI resin, discount resin can not be used for this (or any uses we have) purpose

Water buddy looks good! I have not used it, the idea is right:exclaim: !

Marianne
www.aquafx.net

 

[nasher8860]

Nice thread.. I must of overlooked this one. Great info, and lots of Help!!!

 

[Astro's Reef]

I recently purchased a top off system from spectrapure. The output from my ro/di unit will basically be turned on and off by a pressure switch that is activated when the water level drops 1". My question is will this setup effect my ro/di unit negatively? Constant water in the filters, only flowing when the switch kicks on. Or is this a good thing?
Thanks for all the info here, great thread.

 

[AquaFX]

Level controllers

A top off system is commonly used, the best advice is to keep the unit from cycling alot. Meaning keep the time that the unit kicks on long as possible. Natural osmosis occurs when the unit is not under pressure and the will TDS will actually increase through the membrane make your first slug of water higher than the tap water, (this is eveidenced with an inline TDS meter) so the longer/(less frequently) the unit runs, the better the water quality.

As far as the prefilters, no harm, there is no water running through them so they are not used up.

Let me know if you need more info;

Marianne
www.aquafx.net

 

[Slickdonkey]

What exactly are the implications of not feeding my unit water that is around 80 degrees? Do I just get a lower GPD output or does it cause the membranes to deteriorate more quickly?

I'd rather not have to use hot water as that will run my gas bill up as well (already high).

 

[bc_slc]

Wow, this is a great thread. I have a few questions.

You mentioned that TDS is the only way to know when the membrane needs to be changed. My membrane is probably 2-2.5 years old and has not been changed. About half this time it was used sparingly as my tank was quite small (55gal) and now my tank is bigger (170gal) so my water usage is high. However, I have had the luxury of living in areas with low incoming TDS (usually 50 depending on the rain). I do not run a back flush, and do not have a pressure guage nor a booster pump. I change the sediment and both carbon filters whenever the water output drops off - very scientific, I know....but my output TDS is usually 0ppm and rarely creeps up to 2ppm.

After reading the thread, I think I probably need a guage and a pump (depending on my pressure of course) since a more efficient system would be good. Can you recommend or point me in the right direction for both of these? Money, of course, is an issue.

I was wondering if you could define how you know it is time to change the membrane? Do you change it when you replace the sediment and carbon filters and your TDS stays elevated?

Also, you haven't really talked about the DI portion yet. Can you give some guide as to when to know to change this portion as well?

Thanks for your time,
Mat

 

[AquaFX]

No Problem

Cold Water is just going to slow the production rate down, the colder the slower
Thats all,

Marianne
www.aquafx.net

 

[disbjohn]

does adding a permeatic pump help with TDS creep?

 

[AquaFX]

TDS Creep

The permeate pump manufacturer claims the pump eliminates TDS creep; I have not personally verified it. It does stand to reason; the pump works by changing differential pressure across the membrane. I believe the feed water is feed in “spurts” so there is not a continues steam. so there would be no water avalible. That is my understanding, so if anyone has something to add, please do.

When we reverse osmosis, and then cut the incoming water pressure (usually 38 PSI or greater) osmosis takes back over, in other words the Dissolved Solids pass though the semi-permeable membrane to the side with less Dissolved Solids to equalize or come to a state of rest.

Marianne
www.AquaFX.net

 

[disbjohn]

Are the coconut carbon block filters better than the GAC filters? In my setup, I recently replaced my filters and have a 5 micron sediment filter, GAC filter, then coconut carbon block filter before it goes to the membrane. My TDS after RO/DI is at 10ppm. My Tap is at 360ppm.

Before I had 2 coconut carbon blocks and I was getting about 12ppm before I changed out the filters (9 months). When they were new I was getting 0.

Could part of the reason why I'm getting higher than normal TDS is because I keep my RO filter in the garage in this Texas summer heat?

 

[piercho]

When is a permeate pump most useful? Is it only meant for applications where there are frequent small loads on the membrane, or does it actually improve the performance of the membrane during extended loads? Thanks for your time in preparing this workshop and answering questions.

 

[disbjohn]

from my understanding a permeate pump is good if you have a water storage tank hooked up.