Ro/DI Units. Confused by the ratings

[Jukas]

I'm in the process of shopping for and assembling all the supplies I'll need to do a 60 - 75g Reef Tank and buying a RO/DI unit seems a lot better than paying the LFS $11 for 5gal of pre-mixed salt water, or spending $2 for 5gal of RO water at the local grocery.

I'm a little confused by the ratings however. I see units rated at 25/30/50/75/100 and 200 GPD but no Gallon per minute/hour rating. Taking for example a 50 GPD unit, does that mean designed to produce 50 gallons or less in any 24 hour period, or that it will take 24 hours to produce 50 gallons (1 gallon per 30 minutes roughly).

Aside from the initial fill ups, I don't see myself needing to produce more than 50 gallons at a single time, but the time to produce them is an issue.

[Varga]

ROunits are slow and very wasteful but thats just how it is.

lots of good units on ebay priced right. Filter Direct comes recommended.

also, their ratings are based on 80PSI water pressure, chances are your house has a water pressure of 48-52PSI

[BigAl07]

It's fairly simple. Take the gallon per day and divide by 24 hrs. 100 gpd = 4.1666 gph.

Keep in mind that this is under IDEAL conditions. In cold weather my 110gpd (roughly 4.5 gph) will put out more like 2-3 gph. This is with very high water pressure (we have MASSIVE pressure here in town) where as some people have to purchase a pump to increase water pressure.

My unit took a couple of days non-stop to fill up my 90g Display tank, 29g Sump, 12 Fuge system. Now I only do about 35 gallons for a water change. I start the container (36g) before I leave for work.. check it at lunch time... and turn it off when I get home in the evening or shortly there after.

Just figure it takes 24hrs to meet the advertised rating and you'll be good to do.

What I highly suggest is trying The Filter Guys (who ARE sponsors here) and let them help you get the RIGHT system for your set-up.

Good luck and HAPPY REEFING

[tbittner]

Very true, Al. Cold water REALLY affects the production rate. I got around this by taping both the cold AND the hot lines and mixing them through a John Guest T fitting. The cold is turned on full, then I slowly turned on the hot line until the water coming out of the DI line was around 75 degrees. I couldn't believe how much faster it produces.

I DON'T recommend running like this all of the time though. If something happened to your cold water feed and only hot water got sent through the unit, it would ruin your filters.

[Jukas]

Thanks guys. I was hoping that wasn't the answer but had a feeling it was. I think what bothers me more than the time it takes to make it is the waste. Most seem to have a 3:1 waste ratio and something about the ideal of wasting 300g to make 100g of RO water irks me.

Off to do more research, I appreciate the replies.

[BigAl07]

There are ZERO wastes systems (Can't remember the name) but they demand a higher initial price

[AQTCJAK]

FYI

Poly Bio-Marine Kold Ster-il Three Canister Water Filter

[tbittner]

Yeah Al, I remember reading about that. Someone on here, I believe, mentioned a system made by Culligan. He said you could hook a garden hose to it and the DI water came out with pressure and would fill a 120g tank in like 5 minutes.

It's a zero waste system too.

[Jukas]

Originally Posted by tbittner

Yeah Al, I remember reading about that. Someone on here, I believe, mentioned a system made by Culligan. He said you could hook a garden hose to it and the DI water came out with pressure and would fill a 120g tank in like 5 minutes.

It's a zero waste system too.

I haven't found any kind of system that would perform like that (assuming you weren't being sarcastic), I did however find a new RO unit put out by GE called the Merlin. Still a higher waste system that I'd like, but it's rated at 720GPD with a realistic .35gpm flow without adding a pump.

Price point for the unit is about $400 with the filters being rated for 5,000 gallons. Cost per gallon should be around $.12 for the first 5,000 gallons (paying for the inital unit cost) and $.02 - $.04 gallon after the inital cost (based on replacing filters every six months and replacing the membranes ever 2 years).

If I run the numbers conservatively factoring for only 50% actual useage I'm looking at $.24 per gallon during the inital equipment payoff and $.04 - $.10 beyond that. Not bad compared to $.40 per gallon if I go to a water store, plus gas @ todays median price of $3.75/gal.

The only thing keeping me from ordering that system today is the waste. I've been blissfully unaware of how much water is wasted in making RO water. I'm having a real moral problem being that wasteful especially with CA being in a drought for the last few years running.

If anyone knows of any systems that produce less than 50% waste I'd love to hear about them.

[rbursek]

STOP RIGHT NOW!!!!!!!!!
check out Thefilterguys.biz or buckeyefieldsupply.com and please call them and talk to them to get accurate knowledge and advice. Most of the units on FleeBay have juck membranes in them. Spectrapure I believe is the company that makes one with either 0 waster or 1-1 ratio. Units are rated with 70* water ant 60psi. The 100gpd units and larger have higher TDS out of the RO then the lesser gpd units, you will go thru DI resin faster with those units. It is a bad idea to run a mix of hot and cold water, membranes cook at 110*, someone flushes a toilet, turns on cold water, just cooked it. If you have a water softner get your supply for the unit on softened water. But please talk to the above mention people.

[rbursek]

It is the MaxCap UHE unit that has the 1-1 ratio.

[lcstorc]

Originally Posted by BigAl07

What I highly suggest is trying The Filter Guys (who ARE sponsors here) and let them help you get the RIGHT system for your set-up.

Good luck and HAPPY REEFING

Sorry Al but I believe they are not sponsors.
AquaFX is a sponsor and I am about to set up my new unit from them. I'll lt you know how it works.

Also we are going to be filling large barrels with the waste water to use for gardening etc. There is nothing really wrong with the waste water it is just not clean enough for our tanks.

[Jukas]

Originally Posted by rbursek

STOP RIGHT NOW!!!!!!!!!
check out Thefilterguys.biz or buckeyefieldsupply.com and please call them and talk to them to get accurate knowledge and advice. Most of the units on FleeBay have juck membranes in them.

Sorry if I gave the impression I was going to buy a unit off Ebay, I have no intention of doing so. The prices I quoted for the GE Merlin unit were from internet resellers.

I'll talk to the filter guys and see what they have to recommend, but I'm still leaning towards the new GE unit.

[BuckeyeFSupply]

If you folks are interested in the effects of temperature and pressure on production from an RO membrane, we have a calculator on our site that allows you to enter your conditions and calcualte what your membrane should be producing.

Russ