The video on adding a sump? Yeah..., I give them credit for starting to head in the right direction, however, a few things amiss:
It does not matter in the least which direction bulkheads are installed in the tank; the only requirement is that the gasket be on the flange side of the bulkhead.
For the very reasons they state, "raising the water level," you don't want teeth on your overflow. By raising the water level behind the weir, more subsurface water flows into the overflow, and less surface water (the organic laden layer.) You want as thin of a water layer possible going over the weir. Teeth do not keep critters out of your overflow. Teeth channel the flow, which creates noise.
A small overflow is a disadvantage in terms of the overall system. The move is to very long (full width) overflows that make for far superior surface skimming/surface renewal, which is the whole point of an overflow. One of the biggest issues with RR tanks is the small corner overflows, with teeth.
Never use a check valve, and although the check valve in the video is one of the better designs, the failure rate is still 100%. Flood prevention is done using empty volume in the sump, and a return system that cannot be "bumped" below 1" under the water surface. E.G. loc-line is a hobby toy, and does nothing but restrict your return flow.
Siphon systems are silent. Siphon systems are silent because there is no air allowed into the main drain (otherwise it would be a durso.) However, Herbie's modification is not the only siphon system, there are two: Herbie and BA. Herbie may be ultra silent, (or whatever branding they were trying to place on it,) but it is not stable; (they did not claim it was the quietest.) The "Herbie" as been subjected to forumization, which has resulted in "self adjustment" taken from Bean's design, however this completely short-circuits the safety backup, rendering the system unsafe. BA is also ultra quiet, but it is also ultra stable, and safer. Herbie is/was intended as a modification to allow the installation of a siphon system in a bottom drilled corner overflow. That is the extent of it. The system itself was in use long before Herbie popularized his modification.
The current wisdom is moving to long overflows (C2C,) back drilled tanks, and performance siphon systems, moving past the limitations of RR tanks and dursos, that have been the standard for so many years. If building a custom overflow/drain system, there is no "excuse" to step down to two holes for a "Herbie" when the "better system" uses three, the "better system" is more stable, the "better system" is safer. You have to punch two holes through the back anyway, a third for the return, if you think it is wise to run the return through a bulkhead (more RR thinking.) There is really no point in not drilling the fourth. There also is not really a point to using a small inefficient overflow either.
That said, with a siphon system, 1" bulkheads and pipe will net you 1200gph+, 1" bulkhead with 1.5" pipe will net you ~1500gph, considerably more the closer the drop gets to 36" and beyond. 3/4" is too small, and too easily plugged; the friction losses in 3/4" pipe are excessive. What sizes BRS used is rather irrelevant actually, as copying the design is selling yourself short. There is enough information in Bean's thread, and several other threads for you to absorb and build a custom system that is far more efficient.
The 40 breeder is a borderline tank size. If you are going to push it to 400gph and higher, there would be a good advantage to using a siphon system. On the other hand, if doing what is "common" you will be flowing under 350gph, which a single 1.5" durso will handle quietly, and the siphon system is really overkill. As far as the overflow itself, you are well advised to make it as long as possible, regardless of the type of drain system used.
thank you excellent post have been following site for over a year and my BA has not let me down
The durso works as well but noise is unimportant in the basement. succinct post covers most points..
Agreed a small overflow is a disadvantage in terms of the overall system. The move is to very long (full width) overflows that make for far superior surface skimming/surface renewal, which is the whole point of an overflow.