# Help with overflow plumbing and internal box building



## chiroken (Sep 25, 2007)

This is a pic of my 90/reducer bushing/BH:

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This is my design, tried to get it close to scale, sorry I don't know the fancy programs. The 90 is not bang on scale. Hopefully it is completely labelled to answer my questions. Any problems you see????

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OK, I really need to start drilling holes!!! I have several questions and appreciate answers.

Set-up: 55g 48" tank, I've made a 17g sump. Bean Animal system, 1" bulkheads into 1 1/2" plumbing, only modification I see is to only use 1 gate valve, on the full siphon. Planning on ~ 18" wide internal glass box, to the point of the centre brace edge.

1) Do I need both primer and cement to glue this all together? I thought only glue, or is that with ABS? And this same cement will glue white PVC to my black bulkheads? Guy sold me Uni-weld clear primer and Weld-on 705 PVC cement and Ipex 04 general purpose PVC cement (both clear). I won't mix cements, the smaller cans were on a huge sale so got 2 smaller ones rather than 1 larger one)

2) Space required between front edge of 90's and the front of box (the weir)? 1/4", 1/2"?

3) Unclear about my upturned 90 emergency pipe. What height is it supposed to be at? Will my current design it will be quite close to the top of the tank so I would cut it back. Does it need to be somewhere w.r.t. the top of the weir or just below the tank overflow part?

4) I am using regular 1 1/4 90's with a reducer bushing to connect to the 1" bulkheads. Can I cut back the "slip" part of the 90's to get the 90 closer to the rear wall of the tank, thus making my box smaller front to back? I would also cut back the same distance with the reducer. How much depth is required for glue to prevent air entering the system? (I am comfortable with power tools and understand risks in cutting fittings)

5) Can I cut back the bottom of the 90 in the box to make the box less tall or does that increase likelihood of sucking water and creating noise?

6) Can I cut back the dry end of the bulkhead to save space behind the tank? My BH's have nubs 1/2 down them to stop the pipes from either side going too far (BH's are slipxslip). The dry end is 1 1/8" deep. How much needed to properly glue to prevent leaks and/or air entering?

Thanks tons, I'm excited to get this going, and I appreciate your time in answering.


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## lilscoots (Mar 13, 2012)

1)you do not need the primer, it just helps the glue bond quicker and removes residue that may be on the pvc

2)If you're siliconing the weir in after you've put the bulkheads in, it can be as close as you want to the 90's knowing that you'll never get them out without removing the weir if the need ever arises. I would build a little more height into the weir. I'm not saying this is true, but it seems to me that you'll have quite the time dialing in the full siphon so that it doesn't suck a bunch of air bubbles created from the water rolling over the weir.

3)in my experience, for a 3/4" pipe, the water will rise about an inch above the pipe before it really starts sucking water in. It may be lower for a 1.25" pipe, but I'd still give it some room. I understand you want to minimize the tank space lost.

4) you can, just make sure you get a good glue joint, solid seam all the way around.

5)here's where the height of the box and fine tuning of the full siphon line come into play, with not sucking a bunch of air bubbles.

6)you can again, these lines aren't under pressure so just make sure you've got a good glue seam.

Most of these modifications you're planning will make these bulkheads a permanent part of the tank unless you cut them apart (make useless) to remove them.


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## chiroken (Sep 25, 2007)

Thanks lilscoots.

I bought the primer so might as well use it I guess? The store has gone under so no returns.

I think I will determine the internal box floor once I dry fit the plumbing and can rotate the internal 90.

Hopefully the weir will be wide enough at the flow rate to not create bubbles. It shouldn't make any sound so it shouldn't be creating bubbles, rather, just running over and down the inside weir wall. We'll see!

Will be detailed on the glue joints, to anal to not be 

All joints will be glued as it is required to prevent ANY air into the system or else it won't be fully silent and the full syphon may not self regulate. To remove the bulkhead I will have to cut something external to the tank to be able to remove due to gluing, yes. Must be glued though or air can find its way into the system.


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## lilscoots (Mar 13, 2012)

I run a bean animal as well, my joints aren't glued. some air does get in but the noise from the air isn't louder than the hum of the pump. I have gate valves on the siphon lines and dialing them in to just the right height to be silent even with gate valves takes a bit. In my case, my emergency pipe is too long (I need to cut it an inch or so), so I need to purge my siphon line when I restart after a water change by fully opening the gate valve. Then I need to reset the level after every water change.....you'd think all this trouble would get me to pull the emergency pipe and cut it


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## Narwhal72 (Sep 26, 2006)

I would drill a 1/4" hole in the top of the elbow. That way the siphon will vent and prevent surging within the weir and make it run quieter.


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## lilscoots (Mar 13, 2012)

The gate valve prevents surging, the point is to not introduce air into the siphon line.


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