Need pump advise. What pump will run a ro/di filter?

[Fish]

Hi guys and gals,

I'm sourceing everything I need to get back into the hobby, and was wondering if anyone has experience with rain barrel sump pumps. My plan is to save my ro/di waste water in a barrel and then use a pump inside the barrel to pass it through the filter one more time (just to reclaim a little more water for the tank - if possible).
At a bare minimum, it would be nice if I could thread a garden hose from the pump to a sprinkler on my lawn. This would let me use waste ro/di water and rainwater to water my grass instead of frinking water.
Hopefully, my return to reefing will be marked with a little less waste. ( :

What size/type of pump do I need for this job? 1/2 hp? 1 hp? Something that I can connect a garden hose to - I can easily get a garden-hose-to-fiter adapter for it.
Thanks for the help,

- Chad