Redtibby;683131; said:
I am assuming we are talking about your 55g, right? 3/4" will work for the pump return and can be considered an over kill. The pump you will likely end up with will probably have a 1/2" or less return on it. That dictates the required pipe size going back to your tank. Larger is fine and 3/4 will do nicely. However, it is way too small to go to your sump or wet/dry. Since that pipe is gravity fed, as a rule of thumb it should flow four times what the return pipe flows. By doubling the diameter of a pipe, you get four times the flow. In other words, if your pump output is half inch, then you would want a minimum of one inch leading to the sump. If you have excessive fittings or horizontal runs, you will need to increase this size.
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