RO/DI System

Most home RO drinking water systems like found at hardware, Costco or Sams and department stores are only 15 to 25 GPD which is sufficient for a 3.3 gallon pressure tank but struggles when filling a reef system or ATO reservoir. Add to that they use much lower end, less efficient sediment and carbon filters, many still use granular carbon good for as little as 300 total gallons (ONLY 60 treated and 240 waste since all water passes through the sediment and carbon filters) and you never want to use a pressure tank to feed a DI filter or store DI water in a pressure tank due to its agressive nature.

The short answer is its probably not a good idea since you will exhasut DI resin quickly if you don't make major, expensive modifications. The cost to upgrade a drinking water type system always exceeds the cost of buying a reef grade RO/DI and adding a drinking water kit. In your case you already have the drinking water kit so you could purchase a new reef quality RO/DI for $120, add a tee, check valve and a few feet of tubing for around $12-$15 to tie in your existing drinking water pressure tank , autoshutoff valve and faucet to the new system and have the best of both worlds.
On the flip side a new 90 GPD membrane and flow restrictor is $40-$45, reef quality sediment and carbon block filters is $25, tee, check valve, ball valve and tubing is around $25, inline pressure gauge is $15 and an add on DI filter including cartridge, canister and fittings is around $50-$60 which would make your existing system more like a reef quality system.

 

I thought so here in FL. Not quite. Found .25 phos after a 3 stage filter. It started at 2.0. It seems phos are quite the bane to a reef and tough to get out of a system.

 

Great thread. Answered a lot of my own questions.

 

Even though I think you already made your decision, I still must say +1 to Spectrapure. I had originally bought an Air Water Ice 5-stage system, with filters included. The filters and membrane were exhausted in I believe 6 months (due to #1 the quality of the filters, and #2 not doing my research). After I realized how much money I would waste by buying replacement Air Water Ice filters. So I bought the filters, membrane, DI cartridges, and accessories to essentially create a Spectrapure system in an Air Water Ice's body lol. I do not regret my decision so far, and I plan on replacing them with new Spectrapure filters when they are exhausted. IMO the MaxCap and Silica-Buster DI cartridges, they will save you money in the long run. Do your research!

Things to keep in mind (my major mistakes):
- 0 TDS does not mean your filters do not need to be replaced
- Sediment and carbon filters should be replaced every 6 months on average, a pressure gauge can tell tell you when. These pre-filters will protect your more expensive RO membrane.
- Keep track of your RO membrane's rejection rate (basically how much TDS the RO membrane is removing). This membrane is protecting your easily exhausted, and just as expensive DI cartridge(s).
- NO HOT WATER (I didn't make this mistake, just a warning), the colder the better.
- When system is not in use, keep tubes ABOVE your system. If you don't water will syphon out and your filters will dry out and be useless (I don't think I made this mistake either).

Hope that helps, good luck!