I've read about trying that with PVC Pipe for return lines in display tanks (I think they call them spray lines), and there seems to be a common problem: you won't get the flow of water to be even thru all the holes in the pipe. You will get a lot more flow thru the initial holes and little to no flow thru some of the remaining holes -- this will depend upon the water pressure going thru the pipe of course. Some articles I've read suggest a trial run in a bathtub and start with really small holes and then adjust the hole size along the pipe so that you will end up with an even flow of water coming out of all the holes in the pipe. If I understand what you are doing, you plan to put those 1" pvc pipes beneath a 6" sand bed. How do you plan to keep the sand from entering and plugging those holes when the water flow is cut off?
On using the sand bed to remove the larger particles from the water, it seems to me that a sock is a whole lot easier! Plus, those larger particles will be removed from the system when the sock is removed instead of having them build up in the sandbed.
I assume your QT tank will not be plumbed to/from any other tanks?