bro Zappy Kiwi,
i have tried to DIY a overflow pipe previous but failed terribly thats why i resorted to the " 2 pump system". for my previous DIY, the flow of the water is very very very slow, juz a small stream of water, i am still a student so i cant afford DIYing until it works.
for those who are worried about my tank overflowing i have drawn the layout of how my pumps are placed. i have already tested and its full proof. i cant afford either tanks to overflow as my CPU and sound system is on the floor next to the tank. below is the layout.
if the return pump fails the sump tank will be 4/5 filled, i have drill a hole in the return pipe 2 cm below the water sruface to break the siphon if the return pump fails *touch wood*. if the pump in the main tank fails, there is no holes drilled to break the siphon in the pipe bringing water down to the sump, so water wil continue to flow at a slower rate and the MAX water level at the main tank will be 1 - 2 cm from the edge of the tank.. with lots of mirco bubbles. *touch wood* will be diying a hood to reduce the salt spray.
the worst case senerio will be my 2 pumps burning out thats all ... not floods. juz to need to get a small wave maker incase those 2 pumps does burn out. *touch wood*
btw both my main and sump tanks are 3 X 1.5 X 1.5
cheers
thanks for all the concern