Thinking of adding a sump, need help!

I was thinking of adding a 15 gallon sump to my 25 gallon gallon aquarium to hold the majority of the live rock, heater, and HOB filter. I was looking at doing my own syphon overflow sort of thing with pvc pipe... maybe like 1/2 inch or 3/4 inch. Im worried that my return pump won't match the syphons flow rate. Also what if the syphon for what ever reason stops...The return pump in the sump will over flow the tank. This is going to be a DYI project for me.. not looking to spend alot of money. Any suggestions to get around this? I was looking to get a flow control and just attached it to the return hose but my concern is that if I decrease the flow rate this way that it might damage the return pump? Also would it be suitable to use a 15 gallon plastic "tub" as my sump "aquarium"?. I was thinking of using a tub since I already have one with a lid. Its thick and seems like a very reliable option.