Using a 150gpd system provides 6.25 gallons per hour. After MACNA 2012, I had a 300gpd system on hand and decided to use it as well. Running the two systems side by side speeds up water production significantly, at a rate approaching 19 gallons per hour. I ran it like this for about a year or so, then reverted back to a single 150gpd system. Eventually, I decided to change out the membrane for a 100gpd instead due to the better 98% rejection rating which helped waste less DI resin over time.
Over the years, it has become a bit of an octopus because I have it feeding water to a bladder tank under the kitchen sink to supply drinking water from a spigot, and cold water / ice cubes from the fridge. My blog explains how I set that up: http://www.reefaddicts.com/entry.php/27701-A-fancy-upgrade-to-my-RO-DI-setup
Another line runs through a line over the kitchen cabinets to the fishroom, feeding water to this 265 gallon poly tank and the 45g ATO reservoir. Both containers have float valves, designed to stop water from flowing into the vessel when full. As soon as it is filled to capacity, I close the ball valve at the container and also at the RO/DI system to avoid any accidental floods.
The ATO reservoir is refilled about once a week. The poly tank is filled up every 2-3 months, once all that water has been used up during water changes.
In the picture above, the container is being filled up with RO/DI water. Once it holds 250g of water, I'll add two cases of salt that is rated for 300g. That mixes up to 1.026 specific gravity.
When the poly tank looks dirty, I'll clean it thoroughly before it is filled up with fresh water. Muriatic acid works great for this task. Sloshing it back and forth within the poly tank when horizontal, the deposits and sediment break free and can be rinsed out with a jet nozzle on my garden hose. Tubing directs the water out of the house and down the driveway.
I'd recommend you watch this video to get some additional insight when it comes to making and storing water.