[cottonwool]

I fill it up about half way. If you fill it up with too much water will come out the hand pump. Usually a tiny bit of water will spray out the handpump if you see the water going through the tubing. So I lean back a little and hold the hand pump up higher than the domes so the water will go back down (you also have to hit the air release button a little bit so the water will go back into the dome). Then you can pump and no water will spray out.