waterdrop
Enthusiastic "Re-Beginner"
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What was you other question... well yes, it's the output hose/assembly where the priming suction needs to occur and it's most easily done by disconnecting the spraybar (the spraybar should have suction cups to still hold it in place independently, just slide it sideways in those clips a bit and the output pipe will be handy. I always leave it disconnected from the spraybar while I'm getting the last of the air bubbles out of the system, since it might need a re-prime during this process on rare occasions.
~~waterdrop~~
ps. Raptor, WoW, an extra step! Filtering some old tank water through floss. What do you use as your "filter funnel?" This process would certainly carry the advantage of giving your bacteria safe water in case you got distracted during the period between the cleaning and the filter refill (if left till back at the tank.)