The DI step is not the wasteful step, it is the RO membrane where the waste occurs (if you're talking about wasteful in terms of water being wasted).
I have the unit sold on MelevsReef.com. I've been using it for almost 2 years now and it's worked exactly as it should. It was a bit cheaper 2 years ago when I bought it, but it's still a nice unit.
This unit is also popular with some of the reefkeepers in our area:
$160.00 - OCEAN WAVE+ FIVE STAGE 75 GPD RO/DI
http://www.thefilterguys.biz/ro_di_systems.htm
Personally, I wouldn't advise buying a RO or RO/DI unit with a rating of < 75 gpd. Production rates are based on ideal operating conditions (water pressure and temperature), which many of us do not consistantly meet within our homes. Even if those conditions are met, it still takes roughly an hour to make 3 gallons of product water with a 75 gpd unit. This time of year, even living in the south, actual production is about half of the 100 gpd rating on our RO/DI unit. It's only during the warmer months that we're able to get close to actually making 100 gpd.
I have the unit sold on MelevsReef.com. I've been using it for almost 2 years now and it's worked exactly as it should. It was a bit cheaper 2 years ago when I bought it, but it's still a nice unit.
This unit is also popular with some of the reefkeepers in our area:
$160.00 - OCEAN WAVE+ FIVE STAGE 75 GPD RO/DI
http://www.thefilterguys.biz/ro_di_systems.htm
Personally, I wouldn't advise buying a RO or RO/DI unit with a rating of < 75 gpd. Production rates are based on ideal operating conditions (water pressure and temperature), which many of us do not consistantly meet within our homes. Even if those conditions are met, it still takes roughly an hour to make 3 gallons of product water with a 75 gpd unit. This time of year, even living in the south, actual production is about half of the 100 gpd rating on our RO/DI unit. It's only during the warmer months that we're able to get close to actually making 100 gpd.