Originally Posted by DeviCy
I loved mine at first it self primed very well and after 2 uses it stopped working that way and I have to suck on it, also mine stopped being as powerful and won't suck anything up anymore and I can't for the life of me figure out why. It takes an hour to drain 20% if the tank its that slow it used to take me 20 minutes tops.
You have something stuck inside the bulb or the flapper valve is stuck partially shut. This would prevent you from creating the vacuum to suck the water out. Also if it is partially closed then water flow would be slower.
There are a few methods you can try using to start a siphon that does not have a built in pump.
1. Fill the vacuum with water and lift it up out of the water so that the water starts to flow into the hose. Before the water in the tube is completely drained dump it back in the water keep the opening facing up so that air does not get sucked in. Once the tube is fully submerged and water is flowing you can point the opening down and begin vacuuming.
2. Pour water into the hose while putting your thumb on the output side of the hose. Once the hose and vacuum are full with water go to your aquarium and quickly put the vacuum into the water and lower the hose into the bucket at the same time. Remove your thumb from the hose and the water will begin to flow. Start vacuuming the gravel.
3. If you have a long enough hose that can reach a faucet have one person hold the vacuum in the tank and fill the hose up with the faucet. Depending on how long your hose is you can probably get away with filling the hose halfway with water then stop filling. Allow the water that is in the hose to drain and it should begin to suck the remaining air out and start pulling water.
Remember the higher the tank is off the ground the faster the siphon will work. It is basically gravity fed. If your bucket is the same height as the tank you will not get it to siphon.