Looking for great pond vacuum, purchased Pond Vac 4 could keep it primed when cleaning my 2k gallon koi pond. Maybe I should I read some of the forums first before sending it back. Maybe raising a couple of feet will solve the problem. That said what is the best pond back in the market. My pond is at its deepest point 3 1/2 feet.
There are a few things you should check prior to sending it back, as the "replacements" that you're likely to find will have their own drawbacks (Pond Monsta is a pump on a stick and unwieldy, Matala is twice the price).
The Oase PondVac 4 has a couple of flaws in it, the easiest to detect being the discharge flapper located inside the outlet port. For suction, the flapper needs to be in the upright position until such time that the weight of the water sucked into the canister pushes the flapper down for the water to drain. When the water has drained, the suction draws the flapper back into the upright position.
On the inlet side of things, there is another flapper that is prone to clogging (ie. small stone, twig, etc.). If suction is lost, remove the blue collar from the unit and check that the flapper in the inlet port assembly is clear of obstructions.
Occasionally, a stone or snail shell may become lodged in the handle portion of the suction wand.
Lastly, when you pull the power head from the canister, there are two caged "pistons" or floats (hidden from view behind the removable filter pads). Check to see that these two "pistons", when the unit is held upright, are in the "down" position. Invert the unit a couple of times to ensure that these "pistons" are able to move freely within their cages.
If one or the other is not free-moving, then the cage will need to be removed as there is a cut, one-piece plastic "piston" ring that may have become dislodged from the piston itself. Simply repositioning it back into its intended groove will solve the problem.
