ball valves or not?

[SDguy]

I tip I use also...I give all my vlaves several full turns every so often, just to keep them free of debris.

 

[Fishbulb2]

<a href=showthread.php?s=&postid=8442227#post8442227 target=_blank>Originally posted</a> by sjm817
People have tried to do a "Herbie" overflow on a U Tube setup, and it doesn't work. You cant do the silent overflow thing. A good U Tube overflow is perfectly reliable when used in the normal unrestricted drain fashion.

I don't understand why a Herbie overflow would not work with a utube overflow set up. I was going to try it this weekend. I have two drains in my box and I can cut one shorter than the other. The u-tube will go lower than both of them so as not to break siphon during outages. Then I'll just need a gatevalve to adjust the water level in the rear box so that it is inbetween both drains. The taller drain will just act as a back up.
Why wouldn't it work? I just assume that with the limited space it's too difficult to fine tune with a ballvalve. A good gatevalve should do the trick though.

I also agree that U-tube overflows work well. I don't think the problems with them have much to do with poor design or physics, it's 100% user error. I let my U-tube clog with a huge mat of hair aglae once and that caused a small flood. This was completely my fault though and hasn't happend since.

FB

 

[sjm817]

A couple of people tried it and could not get it to work. A siphon overflow works by the pressure differential between the display level and the top of the drain level. The greater this distance, the better it will work. A high standpipe may not have enough differential to flow.

If you were to do it, starting with an overflow that has a good design with a good spread between the two. I would make the primary drain as low as possible. The secondary drain, no higher than it needs to be.