If water in to your rear chamber doesn’t match water out.. then this will happen.
So, either you don’t have enough water going in (weir comb not big enough) Or your pump is pushing out more than what goes in.
For example:
If you have a weir comb of 4.5cm long (all gaps added up) at 2cm of water height.
you would get, roughly -
4.5 x 2 = total gpm (x60 to get gph) it works out at approx. 240gph.
Check this link out for a good calculator.
My guess is your pump is pushing out more water than your weir is letting in.
I’m assuming you have tried with no media/floss in and had the same result? If not you may have too much media restricting flow.
So, either you don’t have enough water going in (weir comb not big enough) Or your pump is pushing out more than what goes in.
For example:
If you have a weir comb of 4.5cm long (all gaps added up) at 2cm of water height.
you would get, roughly -
4.5 x 2 = total gpm (x60 to get gph) it works out at approx. 240gph.
Check this link out for a good calculator.
My guess is your pump is pushing out more water than your weir is letting in.
I’m assuming you have tried with no media/floss in and had the same result? If not you may have too much media restricting flow.