RO or RODI information please!

[Tabasco1]

Hello there,

I have been looking at an empty 45g cube in my living room for the past couple months as I got side tracked from setting it up with life. Anwyays, I am starting to return my attention to set up again. I kept a FOWLR tank about 9 years ago that did pretty well and am planning on setting this one up with coral. I have most of the vital pieces of equipment. Lighting will be a combo of PC and metal halide, I have an EV Aqua-C 120 protein skimmer and plan on running a refugium as well.

My question is about RO & RODI. I looked for a thread talking about this and couldn't find one that really fit. I also looked for a product reveiw area and couldn't find that either, don't know if there is one on the site, but it would be a great addition. I am an avid mountain biker and mtbr has a great review section for parts and bikes that can suck hours of time like magic.

There wasnt a huge emphasis on the whole RODI think back 10-15 years when I was keeping a tank so I have very little knowledge about this piece of equipment. From what I have read, it is very important to use something that conditions the tap water and that goes a LONG way to preventing alot of issues. I also know that as far as an environment impact that RO is very wasteful, that for about every 5gal of useful water there is 40-90 gallons of wastwater.

Does anybody use a DI system without the RO part? Can anybody make recommendations on a specific filter unit that is a good value and good performer?

Any advice is MUCH appreciated. thanks!

 

[Harry_Y]

"The Filter Guys" (a sponsor here) makes a water saving RO/DI unit

Water Saver RO/DI

That is about a 2 to 1 waste to good water unit, I have one
and have been using it for close to 2 years with great results.

You really do not want to go DI only as it will burn through the
DI material very fast (as in about only 25 gallons of water).

 

[Tabasco1]

I think I did see this answer before, but just to clarify, an RO system that you can have installed under your sink for your home would not suffienciently take down the TDS for acceptable reef parameters?

 

[Harry_Y]

I think I did see this answer before, but just to clarify, an RO system that you can have installed under your sink for your home would not suffienciently take down the TDS for acceptable reef parameters?

Correct, an RO/DI adds an DI stage that should take it to "0"

But, an RO only is better than nothing.

also many of the RO/DI systems can be tapped off after the RO stage
(and before the DI Stage) and sent to your faucet for drinking use.

 

[Tabasco1]

Thank you so much for your help with this. I was looking at the water saving RODI posted above. It was "noted" that a 65 PSI rating on your faucet was neccesary to produce enough pressure to realize water savings.

Do you think that would be the case with any RODI system? Or would the RODI system need to be rated to handle that type of pressure as well? I am not super concerned with having it for drinking water, although could be a plus. I also think that 150 gal/day would be WAY more than I needed to produce.

I apologize if the questions are a bit obvious or mis directed, hard to know what kind of questions are relevant when you don't really understand what you are asking about.

Would this type of system be plumbed in under your sink or connected to your kitchen faucet to produce water only when needed?

 

[Harry_Y]

Pretty much any RO system needs that pressure

it is due to the way the water id forced through the RO membrane

 

[cparka23]

I purchased a new RODI this past year and had to ask a few questions too. I'll be happy to share some of the answers I learned.

[...]I also know that as far as an environment impact that RO is very wasteful, that for about every 5gal of useful water there is 40-90 gallons of wastwater. [...]

It's not as bad as you believe. An RO unit can produce 4 gallons of wastewater per gallon of filtered water, and that's the ballpark figure for a unit. An 8:1 or 14:1 ratio of waste to filtrate isn't something that you'll find these days.

[...]It was "noted" that a 65 PSI rating on your faucet was neccesary to produce enough pressure to realize water savings.

Do you think that would be the case with any RODI system?

The PSI is more for the membrane than for a specific manufacturer of RO/DI unit. So, yes, it's true for any RO/DI system. But it's has to do with how the filters work and does not depend on the brand of RO/DI unit you get.

When the manufacturer tests the membrane rejection rate and claims that it filters 90-something percent of TDS, that measurement is true for the pressure at which the testing was performed. It's a rating, not a design spec that holds true under all conditions. Good water pressure allows the membrane to perform efficiently. If you have low water pressure, you'll have more waste.

 

[Tabasco1]

Hmmm, makes sense. Of course then comes the question of how much psi is generated from my faucet. Any idea on what is standard? Or how to even test for that?

If you don't mind me asking cparka23, which unit did you end up going with? And what was the deciding factor?

 

[Tabasco1]

Oh, and I am curious... sure it is on the instructions, but just to get my head around the logistics of the RODI, is this something that will hook up to your faucet with a hose to run when you need it? Or is it something that you plumb under your sink. I am thinking the latter is only the case with models specifically for household use.

Is the water fairly well contained or is this something of a messy procedure. I live in a condo and have hardwood floors throughout, even in the kitchen. Tile in the bathroom so that could be a possibility.

 

[gilmour01]

Oh, and I am curious... sure it is on the instructions, but just to get my head around the logistics of the RODI, is this something that will hook up to your faucet with a hose to run when you need it? Or is it something that you plumb under your sink. I am thinking the latter is only the case with models specifically for household use.

Is the water fairly well contained or is this something of a messy procedure. I live in a condo and have hardwood floors throughout, even in the kitchen. Tile in the bathroom so that could be a possibility.

you can do either/or when it comes to plumbing it inline or running a hose from your faucet to your filter unit. they also sell booster pumps should you find your water pressure is a little low. i personally have my ro/di tapped into the incoming water line on my hot water heater...then to my booster pump...then to the ro/di unit. My waste water drains into my sump pump and is pumped back out into my yard.

 

[AZDesertRat]

Many vendors who have been around for 25 years or more tried this years ago and gave up on it as membranes need to be flushed or they fail prematurely. FG has not been in existence long enough to figure this out but it will bite them one day.
You need a minimum of 40 psi to operate a RO or RO/DI system and more is better up to around 90-100 psi, membranes are actualy rated up to 150 psi working pressure but the housings and fittings are the weak link.
There are many good reef quality RO/DI systems in the $150-$250 range which include things like low mircon prefilters and carbon blocks, 75 GPD Dow Filmtec RO membranes, 20 oz vertical refillable DI filters, TDS meters either inline or handheld, inline pressure gauges, adjustable flow restrictors so you can set it at the necessary 4:1 waste ratio for best membrane life and performance, and much more.

A few suggestions you might look at are www.spectrapure.com, www.buckeyefieldsupply.com , FL Aquarium Water Filters Reverse Osmosis Booster Pump GFO Nitrate DI Carbon , www.melevsreef.com , www.airwaterice.com and even www.bulkreef.com .

I use only Spectrapure myself after owning 5 different systems over the last 15 years or so. I have mine hooked up with a garden hose adapter wye on my washing machine cold water line and its mounted above the laundry sink in the garage.

 

[Tabasco1]

Perfect. Thank you so much to everyone who chimed in. Helps a great deal. And my future aquatic animals thank you.

 

[Harry_Y]

In referance to "The Filter Guys" water saving RO/DI unit

Water Saver RO/DI

I have that exact unit for nearly 2 years now and it has worked flawlessly in all that time,
I actually get 0-1 TGS out of the RO Stage. I have a 180 + large sump and Frag tank
so you can imagine how much water I go through weekly.

I just changed my DI cartridge for the very first time a couple of weeks ago since I was
changing the other ones (carbon and sediment) I probably could fave gone longer on
the DI but figured I'd just do it (it was still reading 0 on the output).

So since I can speak from true firsthand experience I would have to say it is a good unit.

Mine actually auto flushes every 30 minutes since I added the auto flush kit. It came with
a manual one, but when you make as much water as I do it made it simpler for me.

I originally was going to reconfigure it to Not be a water saver since in NY we have
so much water that it is not an issue, figuring it would make the membranes last longer.
But since it has preformed so well I figured why waste the water un-necessarily.

I'm not really sure how long the RO membranes are supposed to last but at this
rate they should last for years and years.

I don't work for "The Filter Guys" I'm just a Very Happy customer. They delivered when
others could not and have treated me extremely well every time I have dealt with them.

 

[AZDesertRat]

You are fortunate in NY to have extremely low TDS, not many people can say that. This is one reason the unit suits your particular needs but would not work well in many other locations. Again, try contacting one of the other vendors and ask about their testing of low waste systems over the years, they just don't pan out in the majority of cases.

Think about it for a minute. many many vendors have been doing RO/DI systems for years and years. If it were that easy to build a low waste system don't you think they would all offer one? Its not that simple.

 

[Harry_Y]

From my looking at the manuals it appears that Spectrapure's Dual
RO/DI is hooked up the exact same way (as far as the membranes).
Well almost they don't have as many Pre-stages whice make me more
concerned that chlorine could leak past and damage the membranes.

That actually concerns me a lot more since that means id that carbon block fails
(or is not installed corectly) you can kiss goodbye to $100 worth of membranes.

With the Filter Guys setup it would take a major oops
(as in both carbon filters installed wrong or both failing at the same time)
to present the same problem, I'll take the extra stage where it counts.

I can also simply add a second DI stage, but as it is they last forever.

I did a lot of homework (well more actually after the fact) so I am
quite confidant in stating that the Filter guys unit is a good one.

 

[AZDesertRat]

Most of the major RO/DI vendors build a similar system but none promotes it as a water saving device. Membranes must be flushed, there is no getting around it. If you are fortunate enough to have both low tap water TDS and 60+ psi water pressure the dual membrane systems will work but will still have a shorter lifespan than a properly flushed system. I used to run a dual membrane system myself and it worked great as long as i kept my waste ratio at 4:1. Once you start reducing it past that point the dissolved solids in the brine go up significantly and that is what surrounds the second membrane causing it to foul quicker. Its teh nature of the beast.
I'm glad it is working out for you but again your water conditions are not the norm nationwide where TDS levels are increasing all the time due to things like groundwater recharge and treated effluent reuse.

 

[cparka23]

Hmmm, makes sense. Of course then comes the question of how much psi is generated from my faucet. Any idea on what is standard? Or how to even test for that?

In my area, Lowes has a meter that connects to a 1/4" water line for $8, and Home Depot carries 1/2" versions. You'll have to use an adapter to get it to work with one of these meters. I'd be interested in knowing if there's another way, though. Seems excessive just to get a 1-time measurement.

If you don't mind me asking cparka23, which unit did you end up going with? And what was the deciding factor?

I ended up getting a Spectrapure CSPDI-90 over the summer when they had a huge sale going on. They might have another sale before the holidays.

Honestly, it was difficult to tell brands apart. The one thing I liked about the Spectrapure unit is that the sediment and carbon filters are both rated at 0.5 microns. Some vendors have sediment filters that only filter larger sized particulates, leaving the carbon block to do the rest. I think that's just asking for the carbon filter to get clogged more quickly, which means it can't remove chlorine before the membrane and DI.

Also, I didn't have a TDS meter before, so the inline TDS meter was a plus. Now, I consider it indispensable. It can read from the RO and the DI output with a flip of a switch. Wish I had it on my old unit.

A couple more things I learned:
- I used to be concerned about the chloramines that are used by my city's municipal water supply, but there was an old article by Randy Holmes-Farley that put me at ease. You might want to read it, since a lot of vendors have models catered directly at chloramine removal. The last two sections and the conclusion are where you'll find the practical advice.

- There's a phenomenon called "TDS creep" that occurs everytime when an RO or RODI unit has water flow started. On my unit, the first 15 seconds of filtered RO water has a significant amount of TDS. It's unavoidable, so it's a good idea to not have your unit starting and stopping a lot. An under-sink storage tank will lead to the unit turning on and off whenever the tank isn't filled to the max, so it's not good for the lifespan of your filters and membrane.