Just RO not DI - still ok?

[simmlink]

I'm looking for any help I can get on a RO system - so I appreciate any info anyone can provide. I'm looking at a nice RO system, but it's not DI - it's primarly gonna be for drinking water, etc. How important is DI? Is RO without DI still adequate for saltwater?

thanks!
simmlink

[reefsahoy]

with a properly working ro unit you can expect approx 13 ppm tds without the di filter. with the di filter you'll get zero. that's the readings i get with my ro unit before and after the di filter. in florida the maximum requirement is 250ppm tds (i believe). i measured 200ppm

[AZDesertRat]

reefsahoy how did you arrive at a number of 13????
You cannot accurately predict what a properly working system will do without first knowing what their tap water TDS is! Also there is no safe maximum TDS anywhere in the US, its not an enforceable limit set by the EPA or any public entity that I am aware of. 250 is actually the national average for TDS with lots of places exceeding 1000 and very few under 100 and some as low as 50 like Atlanta, you can't put a number to what someone can expect from RO. If you are getting 13 down from 200 thats only marginal at best , it should be only 4. 13 is a 93.5% rejection rate when it should be 98%.
Simmlink, what you can expect is a 96 to 98% reduction in you tap water TDS whatever it may be. In my case the tap TDS is 782 and my RO only is 5.8, much less than 13. RO only does most of the work and is excellent for drinking water but you really need a final polishing with DI for reef quality water. In most cases its only another $30 or so to get an RO/DI over an RO only, of if you do end up buying an RO only places like www.thefilterguys.biz have add on DI kits for less than $40 complete.
My advice to you is avoid e-bay RO or especially RO/DI units as well as most hardware or big box store varieties, they just don't produce the same quality of water and in some cases the components are not worth what you will pay for the unit.
Look at vendors here on RC for some great systems starting at about $149 for a very good RO/DI that will produce reef quality water and its not that much more to add a drinking water kit. I would get the Reef RO/DI and add the drinking kit instead of the drinking water kit and add the DI as the filters are usually better quality in a reef system and will make your DI resin last much longer.

[tgunn]

You may want to check with the local water department to see what the water parameters are before you decide whether or not to use DI.

The city adds PHOSPHATE to the water here to help prevent lead from old water pipes from leaching into the water. Tap water reads 2.0 ppm of phosphate, which is MUCHOS high..

Phosphate isn't removed by the RO filter, you need DI for that.

Just something else to consider...

Tyler

[reefsahoy]

yes, i stand corrected. i should have said i get around 10 to 13 tds comming from 200 to 250 depending on the day, then i get 0 after the di filter. you are also correct that it depends on the input of the ro unit. this will also determine the length of time that the membrane will be effective. the physical unit doesn't determine how good the water will be comming out of the unit just the number of membrane and associated filters connected to the system. i only have a 3 stage ro connected to a di filter and that's probably why i get 10 to 13 tds but the fact is it's zero after the di, it's doing an good job.

[AZDesertRat]

Mine is also only 3 stages before the DI, just a sediment, carbon and RO membrane. The number of stages doesn't mean a hill of beans actually. It all comes down to the quality of what is in the stages and nothing else. I could eliminate the prefilter all together and get the same quality water and probably the same longevity from the RO membrane since I use a 0.5 micron Chlorine Guzzler carbon block. Don't get fooled by the "number of stages" debate, it means nothing. Cheaper units add a post carbon normally only used for drinking water and count that as a "stage" for their supposed reef systems when in fact it is detrimental.

Another thing ,don't believe 0 TDS is 0 TDS, there is a difference! Read the explaination on Spectrapures Sponsors Forum.