Fluval #06 External Filter Why Can't You Refill Before Connecting

[KirkyArcher]

Instruction manual says don't refill canister with water after cleaning/media changing, Connect to Aquastop valve open valve and prime to fill, Has anyone got any explanation as to why filling with water prior to connecting to aquastop valve is a bad idea or has anyone just filled up completely ignoring the advice in the manual and was there any repercussions from doing so? 

 

[levahe]

I have a 306 and I found if I fill it up before connecting it back to the tank, it has trouble expelling air and is noisy and gets airlocked sometimes. Just generally troublesome.

When I connect it back up to the pipes and open the valve it fills itself with a syphon effect and then is very easy to start with minimal air in the system and no problems.

 

[MBOU]

I always fill them most of the way up, connect the pipes, prime it a bit, turn it all on and prime if I need to. I always give canister filters a shake to one side and then the other to get rid of the inevitable bubbles.

 

[KirkyArcher]

The bit that's confusing me is that you can disconnect the aquastop valve remove it from the filter, and then replace it straight away and turn the filter back on and I had no issue (did this when I was about to clean filter then realised I had somewhere important I should have been about an hour previously)