Additional plumbing questions

[castiron]

Long time reader, first time poster.
I have a few more questions for Squidd and others after studying silentshaw's thread.
1. I'm setting up a predrilled 150 that has two overflows with 1.75" holes for overflow bulkheads. Bulkhead: 1.75-OD 1.125 ID threaded. Once I add a fitting I figure the ID will be around 1" or less. Is this what you refer to as a 1" overflow at a 500GPH max? I was hoping to shoot for 10x turnover (1500 GPH).
2. In answering the questions on how far down the tank will drain, no one ever took the return line into account. It appears that not many of you pros use check valves. Without one, wouldn't the tank drain down to the return line due to the siphon effect once the power went out?
3. If that is so, are standpipes even needed on built-in overflows? My over flow is 4.5x8x28 high. That would seems like a lot of dead water volume to me.
4. Did I read once that the rubber of the bulkhead should be away from the water?
I know that's a lot of questions, but I NEED to know.

 

[squidd]

First ...Welcome to the SWF Board Cast Iron...:yes:
'Bout "time" you posted...
1. The 1 3/4" "hole" will give you a 1" ID drain line...which should "easily" give you 600 gph and depending on standpipe choice can be "pushed" to 700 gph...(I have gotten a "measured" 740 pgh through a 1" drain...but it was "balancing" on a razors edge to overflow... )
Figure your two 1" drains will give you 1200gph safely...If you want more turn over than that...start looking at Closed Loop or powerhead supplementation...
2. No "check Valve"...:nope: ..they'll stick..."Return line" can be "safed" with an Anti Siphon hole drilled in tank near water level...No power out back siphon there...
3. Stand pipe minimizes the "dead water" issue from "inside" the overflow box...and sets the water level higher..also helps with "surface skimming" the DOCs from the tank...
4. Now that you mention it, I may have "misquoted" that...I'll have to go back and change it if I did...
"Officially" now..the washer goes "inside" the tank..with lock ring outside...sorry if I caused any confusion...:nervous:

 

[castiron]

Squidd, Thanks for the reply!
You say that Standpipe choice can effect flow. I assume that a wider and taller pipe would give more flow? I dusted off the ol noodle and calculated that a 24" standpipe of large enough area should be able to feed 1664 gal/hr through a 1"dia hole. I guess that's wrong. I'll shoot for 1200-1300 GPH total then. It's going to be FOWLR but I wanted the future capacity for going to a reef.
What are DOC's? The deadspace I was referring to is the 2.5 gallons in the overflow below the standpipe. Just seems like an aweful waste to me.
Help me out with this anti siphon. This is a hole drilled just below water line that would take in air to prevent further siphoning correct? You would lose some return water flow through this then? My predrill is about 1" below the overflow teeth so I'd have to come through with a bulkhead then have a T or something that would go up versus just an outlet straight out horizontally? Any ideas on doing this without looking like crap?

 

[squidd]

Standpipe "Choice"...refers to a straight "drain" (open top) or a looped "Durso style" pipe or a cupped "Stockman" style...
(do a search for those "name" brand styles)...
"Flow" is based on smallest ID (bulkhead, pipe, drainline,etc..) 1" will give you 600-700gph in "gravity drain"...more if "pumped" under pressure but that's a different application...
You will need TWO 1" drains for 1200-1300 gph drain (I think you said you had that)
DOCs are Disolved Organic Compounds often found "floating" on the surface..hence the surface skimming effect of a stand pipe aids filtration...
The whole "area" inside an overflow "chamber" is basicly "deadspace"... no "usefull" purpose other than adding to total tank volume...I use "chamberless" standpipes on my 210...
Antisiphon hole "sucks" air and breaks siphon as you said...small hole, not much "pressure" or flow loss or problems (compared to say a "stuck" check valve...)
My predrill is about 1" below the overflow teeth so I'd have to come through with a bulkhead then have a T or something that would go up versus just an outlet straight out horizontally? Any ideas on doing this without looking like crap?
Are you saying your "return" bulkhead is high on the side, just below water level...? "Inside" the overflow chamber...??
Some how you will need to get the return flow "outside" the chamber anyway...so when you go up and over...drill the A/S hole in the "upper loop"...:yes:
Could be as simple as --^--- with the hole in the ^ ...:thinking:

 

[castiron]

Each overflow chamber has 3 drilled holes in it. 2 at the bottom (drain and return) and the third is 1" diameter with the centerline about an inch below the teeth. My assumption is that this is for the return water. If I run my return water through here, there will be no over the top siphon to drill a hole on. Hmmm......
I suppose I could run the pipe up higher and back down to the 1" predrilled return hole suing 3 elbows. The loop and antisiphon would then be in the overflow box. Has anyone out there dealt with this issue?

 

[squidd]

I "see" what your saying now..the third hole is in the side of the overfow chamber to get return line up from bottom and "out" to tank...:yes:
If you sump can handle the volume you can use that hole, but your tank will drain to that level...
If you want to stop the siphon with less "back wash" you will have to go higher than tank level to break siphon...

 

[squidd]

Just a thought but you could use "both" those holes for standpipes to get quite a bit more flow through the tank and sump...
And then run the "return line" over the top/back and then down to the "side hole"...Put your antisiphon hole in that loop ..:thinking:

 

[squidd]

Nevermind...you already have two overflows and two drain lines...