RO/DI Filter Purchase Help

I am going to buy myself an RO/DI Filter system... What should I be looking for? I have a small (30g) reef set up so gallons/day isn't my biggest concern. More curious about how much of a difference there is between 4 stage rigs and 7 stage rigs. Any models you guys recommend? Any advice would be appreciated or clues to things i might not be thinking about and will need to know...

 

I find that the lower the GPD the better the efficiency of the membrane.
4 stage is Sediment filter, Carbon Filter, RO Membrane, DI.
The first 2 are the pre-filters. Depending on the quality of your tap water and what chemicals are put in it will determine what and how many you need. The sediment primarily takes care of the Sand, Iron and other particulates in the water. The Carbon takes care of the chemicals in the water. Primarily the Chlorine and/or Chloramines.
These protect your membrane from building up with sediment or melting from chlorine.
Membrane does 98%+ of the work.
DI takes the water down to 0 TDS. More or Bigger DI stages are just for ease of maintenance. Cutting down how often you have to change them.

What stages you need really depends on the quality of your tap water. I have had a 50gpd 4 stage unit running for over 6 months. My Sediment filter is still as white as the day I got it. People 10 miles north of me have to change theirs every 3-4months because it turns orange from Iron. I will probably change it out for another carbon stage the next time I change filters to protect my membrane. I have little over 200TDS coming in. 180's going into the membrane and 2TDS coming out into the DI. I haven't changed my DI. Have an extra sitting here from when I changed my Pre-filters.

 

best answer, wait for AZdesertrat to answer. Dude knows his water bump for him

 

Some good advice given here..
A 4 stage unit would be sufficient, however if you have high TDS water then a 5th stage (second DI) would be good insurance to have in case there is any break-through from the first DI becoming exhausted.

Also look for a unit that has a pressure gauge and TDS meter(s). Which provides good info when troubleshooting water quality issues.


Shane
SpectraPure, Inc.

 

The lower the GPD the better the quality is not always the case. While you do want to steer clear of the Dow Filmtec 100 GPD membrane since it is not actually a RO membrane but is considered a nano filter rated at only 90% efficiency versus the 96-98% of their 75 GPD, membranes such as Spectrapures 90 GPD are an excellent choice.

Shane, has some good advice, you need to have an idea of your tap water quality beforehand to help you choose the correct arrangement. RO/DI is not a one size fits all when done properly.

You could go with Spectrapures refurbished system for $128 though and I am sure would be more than happy, many many others here have done just that.

I myself have the dual DI Spectrapure MaxCap system as water here in Phoenix is extremely high in TDS at over 500 but with the national average closer to 250 TDS most can get great service out of the single DI systems they offer.

 

Thanks for the input everyone! I will test my tap water tonight and post the results so maybe that can help give you guys a better idea of my situation. In the mean time ill check out the models listed so far..

 

I have the Spectrapure refurbished 90 gpd 4 stage unit. I live outside of Phoenix and my TDS levels are around 700 and it works great. If you have hard water it is a good idea to run your water through a water softener before the RODI. You might also want to invest in a booster pump if your water pressure is below 50 psi. My water pressure is only 35 psi. Increasing your water pressure will also make the RODI more efficient