Wet/Dry filter questions

[leather]

The hole in the silencer is so the air doesn't get trapped in the downward facing pipe, but doesn't allow too much air in to make a sucking noise. You wont have to worry about it because it goes along with a built in overflow which you currently don't have. If you decide to go the pvc overflow route, which I recommend, you have many options. I have played with a lot of styles some are better than others.

 

[Griller]

is the silencer hole the same hole used to prevent disaster if a power outage occurs or is the hole on the opposite side?

As leather said - the hole is just to prevent siphoning. The safety is determined by the height of the top of your overflow pipe and the capacity of your sump. When power stops the water in your tank will drain only to the top of your overflow pipe. Your sump must have enough leftover capacity to hold this water or it will overflow.

 

[leather]

Maybe you should start with the overflow, and work from there. Get a pump a bucket and build or get an overflow. If you can overflow into the bucket and pump back to the tank and the tank doesn't overflow, then you can worry about building your sump. Just make sure the bucket is about the same height as your sump will be. That way the head lift on the pump (the height the water has to be lifted to) is the same.