gph overflow calculations

[TaylorPilot]

There’s no way a 6” weir is moving 3000gph. According to this a 20” weir, at 2400 gph , will raise water level by 3/4 “

http://irrigation.wsu.edu/Content/Calculators/Water-Measurements/Rectangular-Contracted-Weir.php

And that is without teeth. I have been testing many different designs lately, and I can say with confidence that if a company is selling a 16" overflow and saying it will do much more than 1000-1200 GPH and the teeth aren't 2.5" long, they haven't actually tested the flow with a real flow meter. The weir is almost always 100% the bottle neck on these systems. I am just talking pure water processing ability, this doesn't even get into the facts of trying to keep it quiet enough to have it in your home. A few people are talking about the size of the pass thru bulkheads being the issue, but that hasn't been my experience. In fact, when you get into the larger flow numbers, the smaller passthru bulkheads (1.5" instead of 2") are actually a little quieter. Reason being that there is more of a water height differential between the front and rear box, so I can run the rear box lower for added safety, but the internal box's water level will be higher, and close to the weir, so the water doesn't have as far too fall. There was actually a point in some of the designs where the overflow would be quiet and as you added more flow, it would get louder, then as you increased the flow more, the water level differential would change and the box would get quiet again. Although this wasn't with a normal toothed overflow, it was with our slotted design. I am about to start testing a toothed design to see what kind of numbers I can get out of them. I have tested other brands (not going to say who) that say they will do over 2000 GPH on a 16" overflow with 1.5" drains, and I cannot get them to be quiet at more than around 400-500 GPH without doing some goofy "double siphon" thing, bringing the water level WAY too high in the rear box. But if you are going to do that, there is no point in having 3 drains, and they are not safe to operate. The flow numbers on almost all the boxes I have seen and tested are usually atleast 2-3 times what they will actually flow safely or quietly.

 

[JoshH]

The weir is almost always 100% the bottle neck on these systems

AHHHHHHH, Thank you!

 

[outhouse]

i could be wrong

Oh you are, your dead wrong, but its not in thinking a single drain pipe is limiting you, it can.

You are dead wring for pushing flow beyond its limits. You dont need or want that much flow. 200-400 gph is plenty for a sump on 75, or even much larger.

Do you want a quiet tank? low flow

I ran a 100 with a 1" a made myself, but was smart enough to keep flow low enough for quiet, and function of skimmer.,

 

[outhouse]

, but not so much for skimmers anymore. i could be wrong though.

Well your wrong because your not looking at it right, a corner overflow still getting surface water at 200gph is a lot of danged water in an hour, you dont need insta clean, its not how skimmers work. they dont pull out everything instantly, and many people dont like to over skim. Me I love it, and I have 200-400 gph going to my huge skimmer with 300 G volume tank. More flow only makes problems worse not better