1/2? 3/8? 5/8??? fittings barbs??

[QuietIce]

Hydor L30, max flow: 1200 l/h, max head: 6.5'
MCP-655, max flow: 1200 l/h, max head: 10'

The MCP-655 (NOT the 'B') might be enough to power your loop but I seriously doubt the Hydor will be able to do it. You've got a lot of (total) restriction you're dealing with there and I just don't see 6.5' of head pressure being enough to keep up a good flow rate for that loop.

Also, I don't know what the MTBF (Mean Time Between Failure) is for the Hydor but the MTBF for the MCP-655 is 50,000 hours (almost 6 years). My oldest MCP-655s have been running 46 months non-stop and I expect them to last 7+ years because I don't run them at 100% ...

 

[Weeman]

I agree 100 percent (ish) with QuietIce, thanks for clearing that up. One thing I'm not sure about... if their's air in your resevoir is it still a closed loop system? after all, air compresses and expands extreemly easily, wouldn't that kind of throw off your pressure results?