[Myka]

You do know that RO/DI water isn't suitable for drinking, right? You have to unhook the DI part to just get RO for drinking, and buy the drinking water add-on. You can buy a pressure tank so you get RO water on demand, then just hook up the DI part when you want to make water for your reef. Or you can just use the 20 litre jugs (which are actually 5g, not 6).

Since you're in Surrey, your tap water won't be too bad, so you should look for a 4 stage. One each (in order); sediment, carbon, RO, DI. Imo brands really don't matter much, but the better brands are less breakable as they use better components for their fittings and housings. The cartridges should all be a standard size, so you don't have to worry about the brand of cartridges too much. I wouldn't buy anything less than 50 gpd otherwise it takes a long time to fill up a 5g jug. There will be a flow restrictor in the lines somewhere and it's rating needs to match the RO cartridge's rating. If you decide you want to upgrade to faster you just replace the flow restrictor (cheap), and get a matching RO cartridge when you do your first filter changes. 100 gpd units are less efficient and you will end up burning up your DI quicker. You can buy an optional flush kit (about $15-20) that will flush your RO membrane which is supposed to lengthen the life of the RO membrane. Some people think they work, others don't. I figure for $15, might as well try. The longer and more often you flush the better (like say flush for 2-3 mins after every use).

Bulk Reef Supply has some great RO/DI units that start at $189 I think and they use good fittings and housings. I have an AquaFX Barracuda 4-stage and I am very happy with it...the price has gone up lots in the last couple years though I think they are like $230 now when I only paid $189 for mine a year and a half ago. Generally, if you spend $200 on a 4-stage you will be getting a good quality product. Much less than that and you're buying an econo brand.