RO/DI unit

[H20Sidhe]

I sometimes don't know how to evaulate a good value/dollar spent in this hobby. Does anyone have any constructive/instructive information about this:

http://www.purelyh2o.com/product.php?productid=16210&cat=249&page=1

It SEEMS to be a good value. How are RO/DI units evaluated?

I know I won't be using anything like 75 g a day. So I don't think I need to pay more for a higher gpd production. I estimate my average use to be about 25 - 30 g per week. Of course with a ready source of RO/DI water, I might use more . . . I would like to find something that will produce pure H2O and last a lifetime.

Opinions please.

 

[MrMikeB]

Rating RO/Di units

Rating RO/Di units

RO/DI units should be evaluated (IMHO) based on what you are looking to do with it. For a reef setup, the RO/DI unit is to purify the water from all the nonsense that is there already and/or we add to it (fluoride, phosphates, etc.) - much different than if you are simply looking to drink good water.

When making my purchase of a RO/DI unit for reef setups I looked at:
1) TDS - Total Dissolved Solvents. Without getting into the science, it basically tells you how much 'stuff' is left in the water (phosphates, silicates, etc.) after the filtering process is completed (based on measuring conductivity of the water). The closer to zero this number is, the purer the water (measured in PPM).

2) GPD - This number is widely subjective as what most people don't tell you is that is dependent on your water pressure. Some ratings for GPD are based on an unrealistic pressure coming from your faucet (like 65psi +, but most faucets are low 40s). You can buy a pump to add pressure, but they are not cheap. Many of the 100+GPD models will not even come close to 100+GPD unless you add a pump.

3) Stages - There are many different options, but 'typically' more stages you pass the water through, the more chances you have to filter out the bad stuff. The micron rating on what is being filtered should progressively decrease before getting to the RO membrane (e.g. 1st stage - 20 microns, 2nd stage - 5 microns, etc.). The lower the filter micron rating, the higher the cost of replacing it - so saving them from filtering larger sediment by going through multiple stages prolongs their life and your wallet.

4) RO membrane - This is really the heart of the unit. What is important is the rejection rate (measured in %). This also relates to the TDS, but the more effective a RO membrane is, the higher the rejection % rate, the better the water. Anything below 95% probably should be avoided.

5) Maintenance - How long does the filters last? How often are you replacing it? How much do they cost? Are they proprietary or can you buy them anywhere? Does the unit have a back-flush to get even more life out of the RO membrane?

Hope this helps!

 

[H20Sidhe]

Mike,

Thanks for the excellent info. It fits pretty much with my understanding (except I believe TDS is total dissolved solids, not solvents).

The question comes down to (what I was trying to ask) how does one evaluate the claims made by a manufacturer/vendor about whether a unit is a good value? Is it as simple as word of mouth - someone who has years of experience with brand X, and can say that it performs well, and oh by the way, brand Y is manufactured in the same factory to the same quality control standards as brand X?

 

[distallassazn]

ive actually bought a unit from this place.....
i have no problems with the RO/DI unit. It produced 0 TDS when i first go it.

 

[Brian Prestwood]

Hey Sheri

IMO - an RO/DI filter is like a life preserver. The best one that works is only a little better than the worst one that works. And the worst one that works is infinately better than none. Oh, and the cost difference between the best one and a good one often approaches infiniti.

I'd buy an RO unit that is designed to produce human consumable RO water (like at CostCo). RO units for producing human consumable water have high quality control standards.

Phosphates are a good bell weather. If your tap water phosphates are above 0.3 PPM you'll need a post DI filter to get the make up water below the 0.01 PPM make up water target.

FWIW - I bought a CostCo under sink model ($200), a DIY post DI filter ($50) and a pressure pump ($100). I get great drinking water and great make up water.

A good conductivity monitor (not inline) is a must. I buy bulk DI resin rated for treating human consumable water.

 

[TNTREEF]

Go to Air Water Ice web site.
I believe you can get the 5 stg typhoon for around $139 or so. I've had mine for 3 years now and it works great. It has a 10 mic pre filter then a 5 mic carbon then a 1 mic carbon then the 75 gpd membrane and finally the DI. You will have to also purchase a flush kit and a press gauge. Anything over 50 psi and you don't need a pump.

 

[jlfnjlf]

<a href=showthread.php?s=&postid=8760241#post8760241 target=_blank>Originally posted</a> by Brian Prestwood

A good conductivity monitor (not inline) is a must. I buy bulk DI resin rated for treating human consumable water.

Brian,

Where do you get the DI resin? I need to change ming out soon.

John

 

[MrMikeB]

Sheri,

You might be able to send the seller a request for a spec sheet so that you can see some test results to compare them with others. Unless the tests are shady, you will at least have a little objectivity in your purchase. They should have them readily available I would imagine.

Personally I just purchased a 6 stage unit RO/DIx2 by Water General off of eB** (not sure if that is a bad word here). The tests look promising and are in the upper 99% avg rejection rate and 0 TDS. The cost plus shipping was $125 in Cali, so for the price I am sure its not top of the line, but I can tell you how it works out when I get it next week.

 

[jlfnjlf]

I have the same unit as MrMikeB, and I have no complaints.

 

[MrMikeB]

John,

That same guy (filterdirect) sells the DI resin on the auction site for $18 which is supposed to fill the tubes three times if you cannot find it local.

 

[Brian Prestwood]

John

I bought it at ResinDepot.com. I bought GAC there too. The club or I will will be buying a cubic foot of each next month.