How many stages of rodi do I need?

[reefermad619]

Hey everyone. I'm in the process of building my 80gln tank. I would like to run rodi, even though I've had good luck running treated tap water in the past, and I'm currently having good luck with tap water with my p10gln frag tank. I'm worried that once I set up the 80, that the T5s will cause an algea bloom with tap water. My tap water is ~500PPM. How many stages of rodi do I need to get a gauranteed 0 TDS? Every place I've contacted only recommends a unit, but won't gaurantee 0 TDS. I was hopping someone could share their personal experince with their before and after TDS readings with their rodi and how many stages it is. I was thinking to just buy a 6 stage unit, but why pay extra if I don't need it. Thanks.

[sjm817]

At a minimum,
1 prefilter
1 carbon
1 RO
1 DI

Total 4 stages. If the first two are high quality prefilters, 4 is fine. Most systems are set up with 2 carbon which makes 5.

[RokleM]

Scott's right on. I have two carbon blocks on mine to ensure chlorine is removed. You're right on the too many stages comment as well. Not only is there an up front cost of buying those additional stages that are likely not required, but you also have to pay for the media/filters long term that they hold. That's one of the reasons the crap ebay units are such a joke. Not only are the filters poor, terrible designs, horizontal DI, and other problems... but you have to pay like crazy in the future to swap filters constantly.

It's kind of odd that places won't guarantee 0 TDS. This is actually a relatively simple thing to do on any quality system. What they can't guarantee is how long it will be 0 TDS because every municipality has different TDS, chlorine requirements, etc.

BulkReefSupply, BuckeyeFieldSupply, and an number of other RC sponsors have quality 4 stage units that should do the trick.