How much can a 1" bulkhead flow?

[Neuticle]

Just wondering if anyone knows the maximum flow through a single 1" bulkhead in gph?

I'm looking to upgrade my return and I'd like to go for the maximum.

Thanks

[OneDummHikk]

600 gph gravity fed

[OneDummHikk]

http://www.reefcentral.com/calc/drain.php

[Hop]

Depends on the set up and if you are talking about a drain or a pressurized pump. I'll assume you are talking about a drain. In and of itself about 300-350 gph. If you have weight above it such as a 1.25 or 1.5" durso, up to 600 gph and some people have reported upto 800gph through a herbie style overflow.

1" bulkheads higher up in the tank are a dissapointment as far as drains go.

[Neuticle]

I've got a Mag 5, so at a 5' head I'm probably pushing about 340gph (est.). I was wanting to get a GenX 4100, that would be about 750-800gph @ 5'.

My style of drain is a 2' pipe with diagonal slits all the way up. Currently I have about 3" of water in the overflow chamber.

[OneDummHikk]

With a 1" bulkhead in the tank, you are going to be limited to right at 600gph unless you add a second one. And, adding a larger pipe above the bulkhead gives you a little more waterflow by pressure but its typically not enough to make any real difference. The biggest thing a larger pipe does above the bulkhead is noise issues.

Any chance of adding a second drain?

[Hop]

I still argue that a one-inch bulkhead in and of itself is limited to 300-350 max. It needs oversized plumbing above it. This is why the stockman and durso pipes should be upsized. Here is a link that discusses the shortfall on one-inch bulkheads (http://www.dursostandpipes.com/make-your-own-diy)

It is very common for people to use one-inch bulkheads high in the tank and try to use a c2c overflow or a simple 90 on the bulk head and get terrible performance (less than 300 gph per bulkhead).

And people running the herbie style overflow are reporting higher than 600 gph flows through the bulkhead due to the siphon effect.

[OneDummHikk]

My 90 had a 1" bulkhead inside a 4" square overflow box. No other holes. The standpipe in it was also 1" pvc pipe (no upsize on it). I had to use 1" because the physical size of the overflow box wouldn't let me get a 1.25" or 1.5" durso style drain in the overflow box because of the size of the fittings. It could handle the mag9 at about 3/4 throttle. The mag12 I had to dial it back to a little more than about 1/2 throttle. When I put the mag18 on it, it was at 1/4 throttle but that wasn't max flow, it was where I had it set for the particular skimmer in the sump. Thats my only personal experience with a single drain other than my 20 which has a 1" drain up high and I have not messed with it since it was set up (Its at a friends house). I never ran any kind of test to see how much flow it was pushing but I know it was more than 300gph. Whether it was a full 600gph (which is what the RC calculator says a 1" can handle), I am not sure.

Now, under suction, thats a different story. So far, all my numbers have been for a drain system that drains under gravity. When you add the suction to it, it does increase the flow rate.

I think we can agree, without issue, that a 1" bulkhead is not going to handle 800gph under gravity draining and probably not under suction.

[VWD]

The size of the return pump don't paint an accurate picture here, You have to take into account head pressure. and not only the head pressure of height the water is traveling but all the fiction of bends and fittings.
the only true way to know what a bulkhead will flow is by doing a flow test.

now I think for the most part the tank manufactures pretty much do claim 600 gph. I know that was the info given to us when I was selling tanks

[Neuticle]

Originally Posted by OneDummHikk

Any chance of adding a second drain?

No, I'm not hardcore enough to tear everything down, plus, that tank is retarded heavy. I know dual overflows would really be nice, maybe I'll get a new tank someday...

if my wife dies, lol.

I may see if I can score a Mag 7 or 9.5, just to see how it does.

[VWD]

what size is the tank?

[Neuticle]

It's a 4' 100gal

[Hop]

Originally Posted by OneDummHikk

My 90 had a 1" bulkhead inside a 4" square overflow box. No other holes. The standpipe in it was also 1" pvc pipe (no upsize on it). I had to use 1" because the physical size of the overflow box wouldn't let me get a 1.25" or 1.5" durso style drain in the overflow box because of the size of the fittings. It could handle the mag9 at about 3/4 throttle. The mag12 I had to dial it back to a little more than about 1/2 throttle. When I put the mag18 on it, it was at 1/4 throttle but that wasn't max flow, it was where I had it set for the particular skimmer in the sump. Thats my only personal experience with a single drain other than my 20 which has a 1" drain up high and I have not messed with it since it was set up (Its at a friends house). I never ran any kind of test to see how much flow it was pushing but I know it was more than 300gph. Whether it was a full 600gph (which is what the RC calculator says a 1" can handle), I am not sure.

Now, under suction, thats a different story. So far, all my numbers have been for a drain system that drains under gravity. When you add the suction to it, it does increase the flow rate.

I think we can agree, without issue, that a 1" bulkhead is not going to handle 800gph under gravity draining and probably not under suction.

I suppose there is definitely room for some error on both sides of the arguement. My one inch bulkhead on my fuge would only permit about 300 gph max. I wound up changing it out for a one and a half inch bulkhead and was able to push it up near a thousand gph. This combined with several trouble shooting threads here and elsewhere is where I got my info. Is it steadfast? probably not, but I think it is a valid arguement. Certainly not trying to say that it is the end-all be-all answer. Sorry if it came across that way. Just trying (but poorly worded I suppose) to get the info out there that there may be issues with a single one inch bulkhead achieving the 600gph claim Hope that makes sense.

[VWD]

I would go with the mag 9 over the 7, I always do my plumbing with a tee and valve back to the sump, then you can use a larger return pump and return some back to to the sump if need be.

[Neuticle]

Maximum flow, as derived from the fluid energy equation, for 1" slotted stand-pipe in 25" deep tank. Assuming no friction loss for smooth plastic pipes, and a flow coefficient of 1 for rough flow. Assuming datum at tank base.

25"[(water height above lowest possible entry into overflow)] = -10" [(verticle length of plastic pipe below bulkhead)] + V^2/(2G) [(avg. velocity squared divided by twice gravity)]


V=13.7 ft/s

Q=VA (Flow is Area by avg. Velocity)

Sched. 40 PVC 1" nominal ID = 1.049"

Q= (13.7 ft/s)(Pi x D^2)/4

Q= .0822 cubic feet per second

Q= 296 cubic feet per hour

= 2200 GALLONS per hour maximum under perfect conditions.

Even factoring in a big friction loss, it still comes out substantially larger than I anticipated.

So I figured gravitational flow as laminar instead of turbid

=1100 Gallons per hour max under perfect conditions

that's more like it