Bulkhead Flow Rate

[griss]

Anyone know the flow rate on one of these?

Slip Bulkhead Kit (with Slip Screen And 90 Insert) 1/2' | Premium Aquatics

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[kharmaguru]

Seems like a question for @BeanAnimal

 

[griss]

@BeanAnimal any ideas on this?

 

[reefing102]

I found this on Nano-Reef -
Flow rate chart for overflow bulkhead sizes?

Excluding the argument that occurs in the post there’s a couple charts there that may help?

 

[griss]

Hmmm, that’s a bit interesting. The first chart shows 420 gph for 1/2”. My DIY overflow is 1/2” but the fuge overflows with a 110 gph pump supplying water from the sump????

 

[BeanAnimal]

My math (Bernoulli formula and/or open channel flow calcs) is a bit rusty and I took my calculator down years ago...

Are you trying to run this as a full siphon or with air/water mixed?

Full siphon guessing with all parts (strainer, etc) 300-400gph max to a typical sump 2-3' below the tank.
Quite "drain" with air and water mixed... maybe 75-200 gph before it starting to want to gurgle and siphon. Big range, because it is hard to tell how air enters and where it gets trapped in pipe.

I guess I should put the siphon flow calculator back up at some point in the near future.

 

[Vinny Kreyling]

It would probably help a lot of people Bean.
Me included when someone asks.

 

[BeanAnimal]

It was built in Flash... I just never got around to rebuilding it in JS and HTML5
I will try to get to it this week.

 

[griss]

Thanks @BeanAnimal I was trying to run the DIY overflow as air water to keep it silent, but the flow in is just too much. I found an old fountain pump in my aquarium storage that has adjustable flow so I have that going now but it’s just a trickle.

I was asking about the Lifegard as I can pick one up for under $10. So, if I could replace the DIY with the Lifegard and increase the flow I would do that.

 

[Vinny Kreyling]

Can't go wrong with Lifereef!
I even increased the flow by opening the bulkhead hole larger & used 2 siphons.

 

[wvned]

420 GPH is probably as a full siphon drain.

Your results agree with this in the text.

These results demonstrate that with typical overflow plumbing (that is a straight shot to the sump, no strainers) a:

2 inch bulkhead will flow approximately 1350 GPH

1 ½ inch bulkhead will flow approximately 975 GPH

1 inch bulkhead will flow approximately 350 GPH

¾ inch bulkhead will flow approximately 165 GPH
a 1/2 inch isn't listed though.


I have never used a 1/2 inch. 3/4 is the smallest I install.

 

[BeanAnimal]

Yeah -there are so many variables.

Quickly:
Reynolds number (turbulence) is a huge factor and moreso with smaller pipes. Wall friction creates turbulence (drag that causes non laminar flow where the center of the water is moving faster than the edges). In an open channel, this causes the water to tumble, creating slugs/lenses of water that create partial siphons/suction and gurgle. In a siphon it just slows overall flow by creating more fiction.

Height - the higher the head height on the siphon, the faster it flows. In an open channel, higher head heights just create more turbulence as the water bounces and pulls in more air.

So actual calculations can be quite hard. Often the bulkhead "calculators" are based on the same equation that you would use if you poked a hole in a bucket of a given size and head height... (in other words, most are useless even for a rough estimate).