"I have a 200 gallon tank that I'd like to drain in one hour. Will this Mighty Pump really drain all that water in one hour?"
It depends on a number of factors. The manufacturer says up to 200 gallons per hour can be pumped with this pump. The most critical thing is water pressure and whether you are pumping uphill or downhill. It is best to use the shortest run possible. Also, you will want to take care that there is no debris in the water larger enough to cause blockage in the intake opening (approximately 3/8" opening). This pump must be submersed and it won't work well if you add a piece of hose to the intake.

"I see that you have a link see backflow preventers. Is there a chance that this pump could contaminate my drinking water?"
Yes, and that is why we are mentioning this potential contamination. Most plumbing and health codes do not allow drinking water and non-potable water to be in contact without backflow preventers, such as a Reduced Pressure Zone Back Flow Device. These codes and laws are mandated for your protection. There is a very small (slim) chance that should there be a back siphonage (caused by extremely rare water reversal) non-potable water could go back into the drinking water. We recommend that you use, at least, the above-mentioned vacuum breaker. But we are also stating, for the record, that most codes actually require even greater protection. We recommend that you call your local public plumbing and health code officials and ask what the local codes are with regards to drinking water and non-drinking water pipes/sources being in contact with each other. We in the U.S. take our drinking water for granted. Please be aware of the potential of cross contamination to make sure our drinking waters are always safe.

"Is this pump very efficient?"
This pump "wastes" a lot of water. The pump uses 1 gallon of water for each gallon that is pumped away (water usage ratio = 1:1). We do not recommend it for everyday pumping needs but for those once-in-awhile situations, such as when a pool cover needs to be drained, an aquarium or some other small area with standing water needs to be pumped etc. In these situations, this pump might be perfect for you. In wet areas where you are working and are concerned about using an electric pump with shock hazard potentials, this pump is a great choice/alternative. It is a low cost pump that nearly anyone can use. This innovative product is a great gift idea!