A few questions on RO DI units

[EFSleeper]

Ok so until now I've been getting water from a buddy of mine, but now the time has come to buy my own RO DI Unit. So My question is I'm between 2. I only use 20-30 gallons a week. So any help would be grateful. The 2 I'm between are both BRS units BRS 4 Stage Value RO/DI System - 75GPD - Bulk Reef Supply BRS 3 Stage Space Saver RO System - 75GPD - Bulk Reef Supply. What is the difference in the 2? Also which would be better for the money and the amount of water I use?

 

[redfishbluefish]

An RO/DI is one of the most important pieces of equipment you are going to buy....so I say, do it right. As a minimum I like the "five stage." I like to have a sediment filter and two carbon blocks before the membrane....and then DI. So I say spend a few more bucks, and as a minimum get THIS ONE.

 

[EFSleeper]

I was looking at that one. We tested my tap water and tds meter was only showing 2 entering. That is why I was leaning more towards a 3-4 stage unit

 

[AZDesertRat]

Two carbon blocks are a waste of money. Its not the number of "stages" that is important but what each stage contains.
Take a look at the $130 4 stage system from Spectrapure for $130. It has a 1 micron sediment filter versus a 5 micron for BRS. The sole purpose of the sediment filter is to protect the billions of tiny microscopic pores in the carbon block where the chlorine is adsorbed. Did you know you can see 40 microns with the unaided human eye? Which filter do you think will do a better job of protecting the carbon, 1 micon or 5 microns?
If the carbon is protected by a filter of the same mocron range or smaller it allows it to do its job of protecting the RO membrane from chlorine damage. This also allows the carbon to last its entire 12,000 gallon useful life since it will not be fouled or plugged an does not require an additional filter to act as a second sacrificial filter to catch what the sediment and carbon should have done to begin with.

The Spectrapure also has a specially treated and batch tested high rejection rate RO membrane versus adry off the shelf untreated and untesed membrane that usually is a few % less efficient. For every 2% increase in membrane efficiency you double the life of your DI resin so the cost of ownership goes down significantly.

Then they custom blend every ounce of DI resin they sell and the SilicaBuster resin is the best you can buy anywhere and developed after years of research and both lab and real world testing so it is the freshest longest lasting you can buy for reef use. Then they use only capillary tube flow restrictors so the end user can set their waste ratio exactly as it should be versus the hit and miss fixed type BRS and most others use.

There really is no comparison.

As to your original question, the first is RO only so only gets you 90 to 98% of where you need to be. RO acts as pretreatment for DI which does the final polishing. Youreally need both for reef use. I highly suspect your tapTDS reading of 2, I heve never heard of anything even close to that in my 39 years in the water treatment industry.