RO/DI - Are all equal?

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siggy

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Do you run the unit about 50 gallons at a time, or in short cycles like maybe on a float switch?
Hey there are a lot of good suggestions above, I chose this because it has all that and then some.
This unit has the triple tds, automatic backflush of the membrane, pressure pump, pressure switches and Gage.
I have this going to my freshwater holding tank and I am using a simple float sw so when the level drops the pressure drops on the feed and the rodi pump kicks in, LOVE IT! ....Did I mention it has a CPU that does all this. LOVE IT!
In two years it will pay for itself in resin....one more time?
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Montiman

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Keep in mind RO parts are commodity items the actual filters are doing the work. With two vertical DI Cartridges a pressure gauge and TDS meters you will have one nice system it will be far cheaper to upgrade your current system than replace it completely.
 

ReefGeezer

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...simple float sw so when the level drops the pressure drops on the feed and the rodi pump kicks in...
Every time water is introduced to the RO membrane, a small amount of unfiltered water is passed through it and into the DI media. If your float switch allows this to happen over and over, it will cause the DI media to be expended quickly. It is much much more efficient to fill your fresh water reservoir all at once.
 

siggy

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Every time water is introduced to the RO membrane, a small amount of unfiltered water is passed through it and into the DI media. If your float switch allows this to happen over and over, it will cause the DI media to be expended quickly. It is much much more efficient to fill your fresh water reservoir all at once.
This unit does a small back flush before it supplies any water, it does another large flush periodically, There is a video on the operation somewhere.
FWIW I only do large draws when making SW although was thinking of splitting of the supply to top off the tank. thanks for the tip.

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ReefGeezer

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This unit does a small back flush before it supplies any water, it does another large flush periodically,
I would make sure. I don't have your system so I can't tell you how your's works. Backflushing for me is done manually to clean the build-up from the membrane. It doesn't have any impact on the bypass effect common to all RO membranes.

If the water that is being filtered through the membrane and supplied to the DI Resin is not diverted for a minute or two after pressure is applied, you may be burning DI resin unnecessarily. No amount of filter/membrane changes or possibly backflushes will change that.
 

Water Dog

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If the water that is being filtered through the membrane and supplied to the DI Resin is not diverted for a minute or two after pressure is applied, you may be burning DI resin unnecessarily. No amount of filter/membrane changes or possibly backflushes will change that.
Exactly. That is what I meant by DI bypass and why I linked to that BRS 3 way valve. When a system sits idle, there is something called TDS creep. Apparently, it’s high TDS water seeking equilibrium on both sides of the membrane as the system sits idle. Upon startup, there is a minute or two of high TDS creep water, that if it’s not diverted, goes right into the DI resin, drastically reducing resin life. The three way valve let’s you divert that high TDS water away from the membrane into the drain. You can verify this through properly placed TDS probes. When I start my system up, post RO TDS reads in the 50s, I flip the 3 way valve and Let that water go into the drain for about two minutes. By then the post RO membrane TDS sensor goes back to 1 TDS, I redirect flow back into my DI cartridges and start making water. Using a DI bypass valve will have an incredible impact on DI resin efficiency.
 
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jda

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Are you using 99% rejection membrane? Most come with 90%, or so, and unless you are 100% sure that you paid extra for a 99%, then you probably do not have one. These can really help.

Most of the plastic is of no consequence to me and you can get the same filters in anybody's setup. I just choose to upgrade to 99%, and I will use any unit.
 

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I love my Vertex Puratek Deluxe. Been using it for years and it still rocks!
 
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Otrips

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Can you take another picture of the left side of the membrane (left) so we can verify everything is routed right.

I also have a fountainhead 6 stage system but with the other style (add on) refillable Di cartridges.
When I first receive the unit I noticed a problem, they had installed the lines backwards. The right side was stamped out & had the red (in) line attached & the left was stamped in & connected the the white (out) tube.
This would have caused the water to flow the wrong direction through the cartridges, in center then outside out, vs outside pushed through center & out. I noticed this prior to installing and called Fountainhead the woman was clearly upset they assembled it wrong and sent me 3 replacement filters for informing her of this. She said she was going straight into the assembly room and having a nice long talk with them about this to make sure it didn't happen again. So please check... They are also very helpful with any questions you may have.

So please check to make sure the lines are correct in is in & out is out.
Out then going to the in (cap side) side of of the RO membrane.
On the other side, the short side goes to waste and the long side going to the IN side of the DI resin.
I am not sure the flow direction on your style DI canisters.

Any of that being backwards will cause issues.

You TDS meter should be set up:
1, line going into the unit from your water supply.
2, line out of membrane going into DI cartridge.
3, line out of DI cartridges.

In the correct order to diagnose problems.
Line 1 will be the highest and can vary widely depending on your source water. An unusual spike lets you know there is a problem with your tap water. A problem with your well or contaminates in the municipal system after a water main break or whatnot that you don't want to be forcing through your system.
Line 2 should be much lower and a very low number. This shows how well your pre filters & RO membrane is working.
Line 3 should always show 0. Anything higher means it's time to consider changing out your DI resin.

If line 2 is consistently high check to insure your RO membrane is properly installed & seated inside the housing. After verifying, if it remains high and waste water increases it's time to replace.

Low water pressure will result in lower flow through the system and more waste if there is not enough to push through the RO membrane & other cartridges but it will not effect the purity of the end product or cause excess DI consumption. Rarely is pressure ever naturally to high.

When first using (turning on) always open the bypass/flush valve and flush the system for a couple min. Until line 2 drop to a very low number. It will nearly always spike first before dropping. Doing this will dramatically extend the life of the RO membrane & DI Resin. This is why you want to make larger batches of water at a time & not a few gallons here & there. or connecting directly to a tank's ATO causing it to turn on and off constantly.
another reason not to connect a ro/di system directly to an tanks ATO w/o using a reservoir is if that ATO ever failed (& it will) and stuck on, you would have an endless supply of NSW dumping directly into your tank.


On my system I installed a Y after the RO membrane, before the DI cartridge. w/ shutoffs. This way I can completely shut off the DI cartridge (don't forget as you never want to back flush, drain or let the DI resin dry out) & open the other other valve allowing me to use RO water for various things where I only want RO (filtered) water and not DI water. Such as drinking, filling our Keurig, my other half's soda stream, etc... You would be amazed how much better coffee tastes with RO water. Just don't want to use DI water for that as it's too pure.
 
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Water Dog

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It’s important to understand difference between an auto/manual flush valve on the RO membrane flow restrictor versus a DI bypass valve between the RO membrane and the DI stages.

The flush valve, be it manual or auto, on the flow restrictor of the RO membrane only flushes the waste water side of the membrane. It does nothing on the permeate (product water) side of the membrane.

When an RODI unit sits idle between making water, there is a phenomena called TDS creep. TDS creep resides on the permeate (product water) side of the RO membrane So no amount of flushing with the auto or manual flush valve on the RO membrane’s flow restrictor will get rid of this TDS creep.

TDS creep occurs because when a system is shut down, you have dirty, high TDS water on the waste water side of the membrane and very low TDS water on the permeate (product water) side of the membrane. As a unit sits idle, the low TDS product water on the permeate side of the membrane will aggressively seek to reach equilibrium with the dirty waste water side of the membrane. So as it sits, TDS is drawn from the dirty side of the membrane, through osmosis, until it reaches equilibrium with the clean permeate side of the membrane.

Enter the DI bypass valve. Upon startup of a system, you use the DI bypass valve to flush out the TDS creep water that has accumulated on the permeate side of the RO membrane. This drastically improves DI resin life by not allowing this high TDS creep water to go through your resin. Upon startup, I usually let the bypass run for a minute or two. I make sure to position my TDS sensor between the membrane and the bypass valve so I can see the permeate side go from a high TDS creep number to it normal RO product water number (in my case, it’s 1). After all the TDS creep water has been diverted out of the system, only then will I allow the low TDS RO water go through my DI resin.
 
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Buckeye Hydro

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Needing to change the DI resin after 200G of RO water is definitely not normal.
RO/DI system are pretty straightforward. The brand of the canisters doesn't really matter and everything is in the filters.
I'll respectfully disagree with you on this one, and this case is a perfect example. Regardless of the quality of the filters in that system, I'd never recommend it. Here's why:
1. The configuration is fundamentally flawed. DI filter should never be horizontal, and I'd have little faith in the technical knowledge of a vendor that sells a unit configured like that. Check out their systems on Amazon an you can see a plethera of other configuration errors and less than ideal designs.
2. I believe those clear housings have male threads on the sumps - they are low cost to the vendor, but are notorious for cracking. Not all housings are of equal quality.
3. The system lacks a pressure gauge
4. The system lacks a TDS meter.

Russ
 
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attilak

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Guys, I really appreciate all of this good info - this site is awesome and a wealth of knowledge. The one thing I wanted to say is that I am somewhat new to saltwater aquarium and reefs. I have done fresh water for over 20 years, but just changed to salt water/reef a little over 2 years. The reason why I wanted to say this as at the time I did not know what to look for in a RO/DI system. I went on amazon and just got one with reasonable reviews. So, if this is something I should be looking at replacing I welcome suggestions - I see that there are options to change out my DI canisters to vertical ones and also purchase a better DI membrane. But to be honest I have made mistakes when I try go cheap on equipment and then eventually replace. I feel that I don't want to invest in expensive corals, all my expensive lighting, equipment, etc. and then find out the source (RODI water) is not optimal or waste money on media!

I did take some more pics of the setup and someone on here said they had a fountain head and had issues the way it was originally configured. I do hope that is not the case as I have been running this unit as-is for 2 years now. I just felt that no way I should be replacing the DI resin as much as I do ... and really glad to have posted on here.

Thanks!

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Otrips

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One thing I noticed is your waste drain flows up. It should always flow downwards.
Not sure if you can move the unit up or relocate it to the pipe below.

Cannot tell if pre-filter flow is correct. Mine flows from left to right. The markings are on the top of the canisters right at the end. However it looks like the mount on yours may be covering it. You could take the screws out that hold the unit to the mount and check. The other way would be to pop that sediment filter off let a tiny bit of water flow out to verify the water enters from the outside and out through the center to the next canister & fix that leak while your at it.

Install that other probe between the RO membrane and the DI canister! This is important to know how long to flush the system prior to each use. If you do not flush before EACH use you will burn through DI resin.
 

JoshH

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I hope it ain’t me. :) I’ve tried to explain it the way AZDesertRat explained it to me many years ago. Any additional insight?
Pretty sure it wasn't you lol it's also a pretty simple concept so I'm not sure why SO many people get them confused...
 
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