The base of the tank is full of liquid. The fitting that is screwed into the tank has a suction tube extending to near bottom of the tank. There is no issue priming at these small height differences, as long as there are no breaks or leaks in the line/fittings going to the pump breaking the suction.

The theory behind the design is good, but this tank does suffer from surging issues when below half full. A simple solution to mitigate a good deal of this is to mount the tank at a slight angle(not level). This will keep the fluid from rolling away from the siphon tube too much. I have one customer that used a "whip", frequently seen in the karting world, that has a brass pick-up at the end of a flexible line and this brass unit moved with the fluid staying submerged and preventing the pickup of air. The best advice I can give with this tank is to try to keep it over half full if at all possible and mount it at an angle slightly towards the pickup. I'm not trying to talk you out of the tank, I just want to be honest about our experiences with it.

Pleas note we bought a batch of these long ago just offer as another tank option for our customers. Therefore we have not had any input into the design or overall presentation of the product. I can't say it's always the best tank for the job, but does fill a niche and fit well for certain applications. When the few that we have left are gone we will not carry them any longer as we expect to have our own product design ready to offer in the next 6-12 months.