I'm new here so I hope this in the right place can anyone help I've got a fluval 307 and it's leaking from the prime pump handle getting that stressed about I'm inches away from gluing it closed of course I'm not going to do that I'm just super Confused.
@Silentbadger6310 Same.............but I do have an older one too, i'll have a look at it and see if theres a seal that can be replaced, they sell all sorts of replacement parts for these filters, did you fit the big O ring (motor head seal) that was in packet with the hoses and inlet / outlet pipes to the lid of the main filter ?
EDIT: See picture below.....................
Replacement part:
Fluval 07 Primer Assembley for the 07 range of filters
I had the exact same issue and searched everywhere for a solution but couldnāt find one. The leak was caused by a broken 8mm O-ring inside the motor head (this is separate from the primer gasket and the large gasket on the lid). The only way to access it is by opening the motor head.
Hereās what I did to fix it:
Cut the primer handle ā The primer assembly cannot be removed without cutting the handle (a design flaw by Fluval, in my opinion). A wire cutter works well for this.
Opened the motor head ā I removed five screws: one indented screw near the aquastop and four at the corners.
Replaced the O-ring ā I took out the broken tiny O-ring, filled the slot with Tec7, and let it dry overnight.
Reassembled everything ā Once dry, I put everything back together, and I havenāt had any leaks since.
I found the video below helpful for this process. It also shows the exact location of the tiny O-ring.
I might buy a spare primer and O-ring in case I need them in the future. However, priming isnāt necessary as long as the inlet hose is full of waterāonce you open the aquastop valve, siphoning will start automatically.
Note: Gluing the top shut wonāt fix the issue. Water will still leak into the motor head and eventually flow out from the sides.
of course I'm not going to do that I'm just super Confused. 
