RO/DI Units

[HomerJ]

Hi all:

I'm fairly new to the SW world, and am slowly doing my research before I start buying my gear. 

We have fairly decent water at home (I'm in Gatineau) but it seems like an RO/DI unit is a good idea in this hobby, plus we can use it to stop buying bottled water and treat our daily drinking water.

There seems to be quite a range of prices for what (to me) appears to be fairly similar units.  One Canadian seller on Ebay has a 5 stage kit, 75GPD for less than 150$   Buying the same kit from big box stores would be close to double from what I have seen so far.  What units do people use?  Is there a big difference in quality between the cheaper "eBay" version and the big box store version?

Are there any particular things I should watch for while shopping for such a unit?

Thanks in advance!

[redbelly]

Yes there is a huge difference in the quality of certain units. There used to be a sticky on RC about this but I cant seem to find it at the moment....

Lets look at the diff stages in a nut shell:
1) prefilter - no difference at all here
2) Carbon - First there are several types of carbon. Cheap carbon is made from coconut husk and does not last as long which means you will get pinholes in your RO membrane sooner if you do not replace them much more often.
We have Chloramines in our water in Ottawa so a high quality carbon is an absolute must!
3) RO Membranes - The first thing your membrane will let through is phosphates and silicates. The exact things that you dont want in your tank!
Cheap chinese RO membranes are well know for allowing these through.
4) DI - the biggest diff is actually how it is mounted. Horizontal units allow channeling, vertical units do not. (technically your RO should also be vertically mounted but we are not in a lab here...)

In a nut shell thats it. You can get an entry level RO unit locally for around $200 and a really good unit for $240. Any of the units priced above $240 generally have added features (such as an auto shut off) or added toys (such as inline TDS meters).

IMO you get what you pay for on an RO unit and you dont need to pay very much more than what you initially expected.