Sump pump size...

[sphelps]

Originally Posted by mark

From first hand experience have to disagree that a modified Herbie is a problem waiting to happen. Mine's been up since last October, water in the 2nd chamber can't be that bad as snails don't seem to find it a problem. As for sediment, what's in the overflow is what's left from when I pulled out the Durso. If it was a problem guess I could just siphon out when I did a water change.

Idea for the emergency being a Durso is interesting but since I'll need to worry about flooding at 2000gph if the primary became blocked, I'd be reluctant having the emergency standpipe anything other than a open pipe.

Drain size, here's a calculator for a guide, (towards bottom). 1.5" should be able to handle a Dart.

Well provided it was maintained it may not cause a problem, but why bother adding something that does little good and requires extra maintenance. Using a whole overflow box for emergency reasons only is a waste, 99.9% of the time does nothing but take up space. The reason Herbie overflows have the second drain is because the first is so fine tuned that very minor changes can cause the water to back up but the chances of the primary drain actually clogging 100% is very unlikely. Overflow boxes should always be screened to prevent large enough objects from clogging the drain. Most people don't run Herbies and many only run a single drain, I've personally never seen a or heard of a full clog before with a standard overflow setup.

In addition if you setup the Durso properly it will siphon at higher flow rates and extending the downspout to the bottom of the overflow box will actually add head pressure and will be capable of flowing more than a straight pipe that is typically used in a Herbie setup. Plus on top of that using the standpipe will allow more freedom in tuning, if your flow increases or decreases slightly you will not have to adjust the valve like you would on a typical setup. Lastly by sending some water to the second overflow you eliminate the questionable stagnant issue and you get the benefit of more surface skimming by actually using that second overflow for the purpose it was intended for. There really is no downside to this and I've always setup Herbies in this fashion.