View Full Version : Heresy: A two vessel sump?

salmon alley
09/27/2017, 11:53 AM
Yes, I'm considering this, and let me explain why...then you can tear apart my argument :lmao:

I'm finally getting around to setting up my corner tank. The "legs" of the pie wedge are each 24" and the height is 30". With those dimensions, the footprint is fairly small...large enough to fit only about 10-15 gallon tank underneath the stand. This is too small of a sump for my tastes. I want to have enough room in the sump for a skimmer, heaters, probes, return pump and maybe some chaeto if I so desire.

Since the tank sits in a corner, I could drill through the wall and run the overflows to a sump on the other side of the wall, BUT that would put a bend in the pipe and (possibly) affect the siphon (I plan on running a Herbie overflow).

So..what if I was to run the overflow straight down into the 10 gal tank under the stand, then drill both the 10 gal tank and the larger sump on the other side of the wall and plumb them together with 2" pvc? That should be plenty large to accommodate flow (my return line is only 3/4"), and since water finds its own level, the water height in the 10 gal should be equivalent to the water height in the larger sump.

Yes, I'd have two additional bulkheads which are potential leak/failure points, but are there any other downsides to this crazy idea? Anyone else tried this?

Thanks all!

09/27/2017, 11:59 AM
A bend in the pipe will not affect the siphon as long as no part of it angles upward. In other words as long as all if the pipe has a downward slope you are fine. Your suggestion about linking two vessels is fine, but it adds unnecessary complexity in my view.

09/27/2017, 01:22 PM
^^ what "Simon says" ;) (fun game BTW)

09/30/2017, 07:49 AM
Yes, I would agree with Simon Says, for the most part. It's a little more gray than that IME though. A poorly designed horizontal run, combined with a way too big plumbing diameter, can sometimes result in air accumulation and/or startup issues - the siphon may not be strong enough to suck the air though and you'll have a super hard time keeping the siphon tuned, even if it technically "works" in the sense that the water all makes it to the sump.

That said, it sounds like you're talking about a short horizontal section and you have the opportunity to design it carefully. Try using 45's and making most (or all) of it diagonal. Keep the gate valve near the sump end of the drain. Don't oversize the siphon plumbing - ideally, the plumbing should be JUST bigger than you need, so the gate valve is mostly open.

To put it a different way - a mostly open gate valve on smaller plumbing that is purely vertical will be more reliable and easier to tune than a mostly closed valve on larger plumbing with some diagonal or horizontal sections.