Originally Posted by
Handbanana
http:///forum/post/3281602
Didnt see in there Beasle,
I'm not sure I understand the first part.
I don't understand the unreliable part either. Right now my overflow will only drain what my pump returns. why wouldn't this be the same way for my fuge?
Would it be more reliable in a piggy back situation if I uses two of the exact same u tubes, same in, same out?
Noone ever said I was all the clear on anything.
Ok lets consider both designs. With these parameters:
2 overflows each one capable of handling the total overflow from all pumps and both set to stop draining at essentially the same tank level.
a 30g refuge maintained at 25g level pump runs dry at 3gallons.
a 10g sump maintained at 5g level pump runs dry a 1 gallon.
Now consder both pumps' intakes are in the sump section with the refuge draining to the sump.
Case one drain fails (breaks siphon, plugs).
analysis: water continues to flow down the other drain and the levels in the tank, sump, and refugium all remain the same.
Case two both drains fail:
Refug level remain the same. Sump level goes down to 1g so 4 gallons are pumped to the display. with proper adjustment the sump runs dry before the display floods.
So basically the two drains just provides redundancy to the design.
Now consider the same setup but with one drain to the refug and the other to the sump and pumps in the refug and sump.
Case: the refug drain fails.
Analysis: the refug pump continues to pump down to the 3 gallon level. so 25-3=22gallons of water is pumped to the display.
the sump overflow can handle that so 22 gallons are drained to the sump.
the sump holds 10g and is running at 5 so starts flooding after 5 gallons are drained. With 22 gallons draining the the sump 22-5=17 gallons overflow the sump and you have a 17 gallon flood around the sump.
So in order to prevent that, you would have to fail the overflow to each container and adjust the pump intake height in that container to prevent floods in the other containers. In this case set the refugium pump intake is high enough so it runs dry after only pumping 4 gallons or so.
So in order to prevent floods with overflow failures you not only have to insure the display does not flood but you also have to insure all the other containers do not as well.
Much easier to have the two drains to the refuge and have it drain into the sump.
Or at least having all the pump intakes at the sump. the drains could go to both with less flow to the refug.