Ratsima wrote: ↑Wed May 18, 2022 7:10 am
That effect is negligible, hence I think that the likely cause of the problem is hose kinking, as suggested by Scout earlier.
I was looking into the hydraulic aspects (unusual/interesting case!), besides that you obviously thought about changing the hose as the simplest/cheapest possible solution. It's difficult to see how would a few mm diameter reduction ruin the flow rate. I used vague assumptions with the only data being the hose size, so the figures certainly can be off & wrong.
Just knowing two flow (=pump discharge) rates, for 'clean' and 'dirty' conditions would help understanding the situation. Can you do a bit of engineering, please? The measurement is simple & easy: mark say 10, 15, or 20 L water volume on some bucket/container, then measure the time (seconds) to fill that volume by the 'fountain' outlet jet.
With those data much would be revealed already, though also would be useful to know the:
- length of the hose
- static lift (elevation difference between the water surface level in the pond and the end of the hose (discharge point)
- immersion depth of the pump
I guess the Chinese don't provide the Q-H (performance) curves for their pumps but for such type of pumps those all look very similar/simple.
Such data (or estimates) are important because changing the hose diameter also changes the pump working point (pump fdischarge and head).
The ultimate cause of the problem is evidently biofilm growth but discussing the reasons and management options IMO can wait for the hydraulics results. It suffices to say that there's no algae problem -> using any algacide would be a mistreatment.