der_wille_zur_macht
Team RC
Which is what bred my suggestion above. Perstaltic is pretty much going to be the only option worthwhile, since any centrifugal pump capable of that head will probably be expensive and pretty high flow.
If you don't want to go straight to the sump with your RO line, do you have enough room up by the sump for a small reservoir?
Though I understand the potential dangers of running the RO line straight to the sump, I also feel that it is pretty easy to safeguard the line from flooding. The best way to do this would be to use multiple methods to turn the line on and off, i.e. a float valve as the main control - plus a float switch and solenoid higher up on the sump to shut the whole RO unit off if things got out of hand. I've been in situations pretty much identical to yours and run tanks this way for years without problems, as have plenty of other reefers. It might not be 100% ideal, but it definitely works with a large degree of safety if you're careful.
