So my set up is simple: 2 x 20l tubs of rain water to y splitter> in-line strainer> shurflo 100psi pump> 4.6 litre di vessel>hose reel It all works fine, the only problem is when I'm cleaning windows and the tub empties....the pressure out the pole drops which is understandable but when I go back to change tubs, the pump is running constantly and basically sucking up air and creating a huge airlock in the system. the best way I've found to lose the airlock is disconnect the hose between the di vessel and hose reel and run it for a few minutes while it coughs and splutters and finally the water starts flowing again. Obviously this isn't ideal as I have to wait a good 5 minutes every time this happens, does anybody have any suggestions on how to avoid this problem as it's really slowing me down. And no, a tank is not an option! Thanks in advance!