Flow rate discrepancy

[kkutac001]

The flow calculator at RC shows I'd need 11 inches of linear overflow with a 1 inch drain pipe in order to drain 700 gph. I just read a thread on WWM where Steven Pro said each 1" bulkhead can "comfortably handle" 300 gph.

That is quite a discrepancy for such a critical calculation. Anyone here got the straight skinny on what the truth of the matter is?

[Ram_Puppy]

I believe WWM, I have a 1" and a 1.5" bulkhead on my cube and I can open the valves wide open and let the reeflo dart go to town...

while I am sure the dart is not pushing it's full 3200 GPH, I am sure it is over 2500 GPH... I know it's a subjective analysis... sorry.

[kkutac001]

Sorry, I'm confused Ram_Puppy. If your flow is over 2500 gph, then neither the (low) WWM figure nor the (higher) RC calc figure can be correct. (The RC calc shows you'd need 2" and 38" of linear overflow)

[witecap4u]

one of my drains clogged on my 100gal. the other one was able to pickup the slack though. Drains are 1" and pump is probably pushing 800-1000gph.

[Ram_Puppy]

I am confused too. :)

[kkutac001]

heh. Confusion can be the precusor to understanding. Or so I hope. -- whitecap4u : thanks for your info. I was planning to drill two 1-inch holes, and to pump something like 700 gph (give or take). I thought having two distinct 1" drains would make it plenty safe, as well as allowing some future increase in turnover, should I wish to do so. (700 gph would be about 8x turnover) After hearing from you, I think I can feel good about my planned drilling activites.

[Magneto]

I always heard 900 gph is what a 1 inch hole could take. Could you provide a link to the thread so we could get a little context on what Steven Pro said. He also has a forum on marinedepot forums and has always seemed pretty knowledgable. You could ask him to clarify there easily.
We could all be right. As in 900 is the max and 300 is a comfortable amount inside the range of 0 - 900. Could be he meant that at 300 GPH there would be little back pressure thru a 1 inch bulkhead.

[duc]

I have 2 1" holes and "had" a 1200gph pump hooked up which (even with head pressure) I had to throttle back. I would guess with 90's and depending on drain hose length 450 per is a max and 300 is a realistic, if you go 450 and one gets blocked you are in for a world of wet.
Clif

[kkutac001]

For Magneto: Here is the link, and I found where Calfo gave the same figure (300 gph) on this same page. I'll nip out the text for convenience.
http://www.wetwebmedia.com/pbmarfaq2.htm
Calfo : "...generally...a 1" overflow can handle up to 300 gallons per hour comfortably without creating a noisy siphon"
Pro : "Each 1" bulkhead can comfortably handle about 300 gph. I have and would recommend drilling 3 holes in a 75."
From reading the two, it looks like "comfortably" means having no noisy siphon noise, so you're not 'driving it' too hard. But I thought a Durso arrangement would take care of that. And I still can't reconcile duc's statement with, say, witecap4u's. These two didn't have all that much difference in gph, had the same two 1" holes: duc said that was a problem; witecap4u says one clogged and the other picked up the slack. I have read/heard that some pumps do not handle back pressure well. Maybe something like that (i.e. a variable we're not seeing clearly) is making a difference in how people have experienced their 1" holes.

[Ram_Puppy]

I wonder if calfo is talking about a more traditional arrangement. A durso, and designs similar to the durso, make significant headway towards quieting a tank...

now, I personally think there is a bit to much flow going through my sump, but I can't see that I have much choice in the matter now, I made a design judgement in the beginnig that was flawed. I went with the bigger standpipe because I wanted a low energy pump (the dart) that was quiet, and I never thought of just dialing back the pump.

Anyhow, the flow in the main system is awesome so I guess I can't complain... hope it stops re-adjusting the sand bed once I get more rock in it! ;)