Silent and Failsafe Overflow System

[wonrib00]

I tried to use a standard CPVC plumbing fitting and had a heck of a time finding a tap bit that matched it. The threads/in on the tap bits did not match any of the fittings. I ended up having to buy a brass fitting that matched the threads of the CPVC fitting and tapping it by hand with a wrench. I couldn't find a "John Guest" fitting at the HWS maybe that was the issue. But anyways that is how I figured it out. It wasn't pretty, but it worked.

You may want to rethink that brass idea. Brass and saltwater don't mix well. You may get away with it if you seal it some how with some sort of sealant, but you may want to nix the brass and glue the fitting into the cap. It all depends on your comfort level. I for one would not be able to sleep.

 

[Floyd R Turbo]

I just tapped it using the brass fitting because the threads matched, then I took the fitting out and out the CPVC fitting in.

 

[BeanAnimal]

The threads on most standard plumbing fittings are NPT. Harbor Freight sell fairly cheap NPT taps, as do many ACE or TrueValue hardware stores. I rarely see them in the big box stores.

I have also used a brass or steel fitting as a tap for plastic. Not ideal, but it works in a pinch.

 

[Floyd R Turbo]

Well the BB store is where I was. I did notice a much larger selection at Ace when I was there the other day finding a 1/4-20 tap for tapping acrylic. Thanks for the heads up, I will definitely remember that!

 

[SouthBayPhoto]

Just some thoughts on a cheaper tap & die set at Harbor Freight

http://www.harborfreight.com/40-piece-sae-carbon-steel-tap-and-die-set-39391.html

http://www.harborfreight.com/40-piece-metric-carbon-steel-tap-and-die-set-39384.html

http://www.harborfreight.com/21-piece-carbon-steel-tap-and-die-set-96570.html

I'm sure one of those should work for you and they aren't that expensive at all. First one is SAE, second is Metric and the third a smaller SAE set. All you would have to do is take your fitting down and match it up with the ones they usually have on the wall (most big box stores have a wall where you can screw your fitting in to verify it's actual size) and then you know what size you actually need and then go get the set that contains it. I'm sure the 40 pc set has it for you though.

 

[SouthBayPhoto]

Since you just mentioned the size while I was posting, both the 40 pcs & 21 pcs SAE sets have 1/4"- 20 in the sets.

 

[yousmellsfishy]

Given the size of this thread, maybe this has been covered before, but I've read most of it and don't recall this being asked before. Isn't it true that everything up from the sanitary tee is so that the tubes can be easily cleaned? If I were to build my overflow box with the bulkheads on the bottom, couldn't I have 90 degree elbows on top of the tubes coming up from the bottom and connect the street elbows on to those, and just not glue the pipes into the bulkheads? The pipes coming into the overflow from the bulkheads could be pulled out for cleaning the pipes, and any trivial leaking due to not gluing would only leak water from the overflow into the drain tube and down into the sump. No harm, no foul.
? ? ? ? ? ? ? ? ?

I am aware that just about every suggested modification to the original design is a fail but I think this would be fine. The john guest fitting could be placed on the open circuit on top of the 90 elbow.

 

[uncleof6]

Given the size of this thread, maybe this has been covered before, but I've read most of it and don't recall this being asked before. Isn't it true that everything up from the sanitary tee is so that the tubes can be easily cleaned? If I were to build my overflow box with the bulkheads on the bottom, couldn't I have 90 degree elbows on top of the tubes coming up from the bottom and connect the street elbows on to those, and just not glue the pipes into the bulkheads? The pipes coming into the overflow from the bulkheads could be pulled out for cleaning the pipes, and any trivial leaking due to not gluing would only leak water from the overflow into the drain tube and down into the sump. No harm, no foul.
? ? ? ? ? ? ? ? ?

I am aware that just about every suggested modification to the original design is a fail but I think this would be fine. The john guest fitting could be placed on the open circuit on top of the 90 elbow.

Yeah that would work. But I would NOT leave anything unsealed in the system--just bad form. Get bulkheads with FIPT on the flange side. Use teflon paste to seal it--or not. It is far far easier, to use tees and screw on caps, than messing with the whole dang thing to clean it.

 

[radone]

Curious to know if this can be done on my setup
I have (3) 1 1/2" bulkheads in my overflow box, the overflow box is approx. 14" deep.
As of now I run durso's and have no problems but would like to quiet the system down, babbling water sound.

The left hand durso feeds my skimmer and returns unused flow to the sump
The right hand durso just returns to the sump and the middle I don't use yet.

Does it matter the location of the suction, open channel or emergency line as I really don't want to have to re-plumb this thing.

Any suggestions much appreciated

 

[radone]

Curious to know if this can be done on my setup
I have (3) 1 1/2" bulkheads in my overflow box, the overflow box is approx. 14" deep.
As of now I run durso's and have no problems but would like to quiet the system down, babbling water sound.

The left hand durso feeds my skimmer and returns unused flow to the sump
The right hand durso just returns to the sump and the middle I don't use yet.

Does it matter the location of the suction, open channel or emergency line as I really don't want to have to re-plumb this thing.

Any suggestions much appreciated

I run a dart for return pump too

 

[JTL]

I have never been able to get the full siphon to kick in without some intervention. I have had problems on two completely different tanks. I know it is something I am doing wrong. I have an internal overflow and the plumbing is all 1". The vertical drop from the overflow is about 2 1/2' and then the drain runs horizonal for 3'. Both the full siphon and the open channel are the same distance and size, the only difference is the full siphon has a gate valve. The problem is that the open channel rules, even when it is not in siphon mode. Only thing I can figure out is the gate valve is causing too much of a restriction. I don't think anything is stuck in the valve because when it does get into full siphon mode it has a lot of flow, even with the valve cranked down. One other thing, opening the gate valve all the way open does not help to get the siphon started. If any has some thoughts please let me know. My next step may be to remove the gate valve and see it something is wrong. Unfortunately I have to cut it out since I neglected to make it removable.

 

[BeanAnimal]

JTL,

In a nutshell, your setup significantly deviates from the original specification. You have used 1" plumbing AND added a horizontal run. The air trapped in the horizontal run is likely the problem, as is the fact that the open channel is not an open channel due to the horizontal run. I am not sure how to help, as the are far too many variables that I am not able to see.

 

[afgun]

How far under the water surface does your siphon extend? If it's more than one inch that is assuredly a contributing factor. When I had a flow restriction through my bubble trap (long story) the skimmer section of my sump had water several inches higher than normal and it would take several minutes for the air to clear from my siphon line and things to settle down.

 

[bbwebb]

Overflow help (or confirmation)

Overflow help (or confirmation)

First off, thanks to everyone who participates in this forum. The amount of information sharing is staggering and there is no way that I would be anywhere near close to making a purchase if I had to rely solely on books or magazines as I did back in the early 90's with the hobby.

I'm hoping to put my order in at Reef Savvy for my new tank sometime next week, but was hoping to get some feedback on my overflow layout first. This will be by far the largest SW/Reef tank that I have ever built and that has really opened up some options that I had not considered in the past.

I've spent weeks pouring over this thread and I think I understand the physics at work here, but I would love some feedback from the experts. Also, please ignore my modeling skills. This was my first attempt at using Google SketchUp and I still have a ton to learn. Fantastic app though, especially for the price (Free!).

Here are some pictures prior to my questions:

The weir is ~37" across and 1.25" below the top of the tank. Does the 1.25" seem appropriate? I struggled with trying to determine how close to the top of the tank I wanted my water level to be and still have a couple of MP40s in the tank creating small waves.

The overflow is 42" x 6" x 6". Any thoughts or concerns?

1" bulkheads are specified for the overflow. Is this sufficient for a 100G tank?

Finally, right now I have just one return bulkhead specified. What's the best practice in this regard? Should I add another on the opposite side? I've also spec'd 1" bulkheads for the return. Does that make sense?

Bill

 

[dirtefish]

Been searching for a bit, but havent found the recipe for overflow box sizing.
Plan on running 700-800gph through the box and was curious on the min length for the overflow box to keep the siphon channel fully submerged.

Everything is planned excluding my box, just waiting on some help on dimensions to allow proper flow.

Be an animal-
Your insight to the hobby is amazing. Thank you for being the animal you are!

 

[Floyd R Turbo]

The overflow is 42" x 6" x 6". Any thoughts or concerns?

1" bulkheads are specified for the overflow. Is this sufficient for a 100G tank?

Finally, right now I have just one return bulkhead specified. What's the best practice in this regard? Should I add another on the opposite side? I've also spec'd 1" bulkheads for the return. Does that make sense?

Bill

I would opt to make the external box deeper. The tank I run the BA on has the overflow on the end, and maybe that's part of it, but the weir dumps about 1" down into the box (16" wide 3000 GPH) and I needed something inserted into the box to 'break the fall' to prevent air from getting sucked into the siphon. Maybe 8" deep.

Also is this an acrylic tank? off topic, but cutting the back of the tank like that and disconnecting it from the euro (which is way, way to narrow) mean your external box is structural and needs to be pretty thick.

And for what it's worth, I would go to Miracles before Reef Saavy any day.

 

[Floyd R Turbo]

Been searching for a bit, but havent found the recipe for overflow box sizing.
Plan on running 700-800gph through the box and was curious on the min length for the overflow box to keep the siphon channel fully submerged.

Everything is planned excluding my box, just waiting on some help on dimensions to allow proper flow.

Be an animal-
Your insight to the hobby is amazing. Thank you for being the animal you are!

The formula you are looking for is a fluid dynamics equation for flow rate over a weir. It looks like this:

Q - flow in GPH
C - discharge coefficient
L - length of weir (either slotted or not, total water flow distance)
H - height of water above weir (or bottom of slots)

Q = 288 * C * L * H^(3/2) <--square root of H cubed

If you are running a weir, then C = 1.00. If you are running 1/4" width slots, then C = 0.55.

So if you have a slotted overflow with 10 1/4" wide slots and the water is 0.75" above the bottom of the slot (like 1" teeth running with the water 1/4" from the top) then

Q = 288 * 0.55 * (0.25 * 10) * (0.75)^(3/2) = 257 GPH

At 1" Q = 396

a 1/2" (h=0.5) weir (C=1) of width L=2.5" (same effective width as 10 slots) is 720 GPH

HTH

PS I just read what you were asking again. Not sure this helps, but your question is regarding how long the weir has to be to keep the overflow box full enough to keep the siphon submerged. I hope this equation answers your question, if it does not, let me know

 

[JTL]

JTL,

In a nutshell, your setup significantly deviates from the original specification. You have used 1" plumbing AND added a horizontal run. The air trapped in the horizontal run is likely the problem, as is the fact that the open channel is not an open channel due to the horizontal run. I am not sure how to help, as the are far too many variables that I am not able to see.

Why would the 1" plumbing make a difference? As far as trapping air goes I can remove part of the pipe above the water line and it still doesn't siphon and the open channel has a lot of flow even though the pipe is below the water line in the sump.

 

[Floyd R Turbo]

pics would help tell the story a bit more. I can't envision everything you described so advice you're being given may be wrong.

 

[uncleof6]

Been searching for a bit, but havent found the recipe for overflow box sizing.
Plan on running 700-800gph through the box and was curious on the min length for the overflow box to keep the siphon channel fully submerged.

Everything is planned excluding my box, just waiting on some help on dimensions to allow proper flow.

Be an animal-
Your insight to the hobby is amazing. Thank you for being the animal you are!

It is really far simpler, the little calculator on the home page of RC? It is close enough, if you figure no teeth, double the length if you use teeth. 12" minimum for the overflow length for 800 gph. See below.

Keeping the siphon submerged is a relatively uncomplicated thing. It does not take weir calcs, or any fluid dynamics really. This system is adjusted by a valve in the siphon line. By closing the valve, the water level in the overflow rises. The system is adjusted to the point that water just flows in the open channel. So regardless of the flow rate, and weir length, the siphon will remain submerged.

The length of the weir comes into the mix when we consider surface skimming, and the water level as it goes over the weir. Too short, and the water piles up. Teeth cause the same condition.

The higher the water level as it goes over the weir (1/2" above compared to 3/8" or 1/8",) the less surface skimming there will be. This is because the velocity of the flow is higher the closer you get to the weir itself. (*Still waters run deep*) Although the surface water will go over the weir, more subsurface water is flowing, and less surface water--increasing the time it takes for the surface water to be removed (this is where the organics are.) So the thinner the waterfall the better the surface skimming, and the longer the weir, the thinner the waterfall, at a given flow rate.

Ultimately, for any given tank size, and any given flow rate, the ideal system will have a full length weir--end to end, or Coast to Coast as it is called. With the possible exception of a zero edge aquarium......