Desperate plumbing/closed loop questions

[heedicus]

Hello all,
I am helping set up a 800 gallon sps tank. We are planning on using 2 main circulation pumps a sequence hammerhead and a dolphin pump rated at 7800 gph at the head pressure we are using it. When we fired up the main 7800 gph pump the slots in the overflow couldnt keep up! The tank started to overflow even though the waterlevel in the overflow was keeping up and was almost at the bottom. The tank is 4 feet wide and the slots go the entire width of the tank.
Does that sound right or should the slots be able to keep up wtih the pump?
My thought was to drill a 2 inch bulkhead and run the 7800 gph pump as a closed loop but the worry is that 2 inch pipe couldnt keep up with the pump (it has 1.5inch in and out). Could the 2 inch piping keep up?

Thanks,
tren

[Mr.Lloyd]

A single 2" drain screen would suck fish onto it like crazy.I use a single 2" on one of my closed loops with an Ampmaster 3000 and it pulls hard.Aquatic Eco Systems sells some bigger screens and bulkheads.I would think you would want at least 2 just so you could not clog it.An Oceans Motion 4 Way or two can give you great water flow.I run 2" in and 1 1/2" out.I actually have 4 loops on my 300 that has a 325 agricultural tank with extra rock.1 is a under the tank sump with assorted equipment that uses the overflows and returns via 3 ports through the bottom.2 is a closed loop with three Seaswirls run by another Ampmaster 3000.3 is a closed loop with OM 4 Way with Ampmaster 3000.4 is my loop to the big ag tank and back.I run 2 Blueline 40's going and coming with valves for flow adjustment.
Enough about what works for me.Use your overflow as you can for surface skimming and go with big multiple bulkhead sceens.You can plumb an OM 4 Way back through bulkheads if you want.

[heedicus]

yea I was just thinking the same thing,
I have a sequence hammerhead going through a 2 inch inlet it does have some suck so I would probably have to do at least 2 to minimize the suck i guess.
anyone else?
t

[john rochon]

I have 3! 1,1/2'' inlets for my hammerhead.

[ckaldahl]

Cut every other tooth out in the slotted overflow to increase its amount it can handle.

[chriscobb]

I would probably widen the teeth on the overflow to allow it to take more water or worse case you could put a ball valve on your pump to throttle it back!!!!

[clenahan]

Originally posted by heedicus
< snip >
Hello all,
I am helping set up a 800 gallon sps tank.
< snip >
The tank is 4 feet wide and the slots go the entire width of the tank.
< snip >

Did you mean 180? If you meant 800 , out of curiosity, what is the dimension of you tank?

[hotcereal]

Im gonna take a guess and say that the foot print is 4 ft wide?

[chask]

You ought to look at the flow velocity.

7800 gal/hr x 7.48 ft3/gal = 58,444 ft3/hr or 16.2 ft3/sec

Pushing 16.2 ft3/sec through a 2" diam pipe (.021816 ft2) => a flow velocity of 743 ft/sec. This is very fast - a little over 506 mph if my math is right (someone ought to check me here - sleeping problem lately and I am about half awake) .

Mr. Lloyd wrote:
A single 2" drain screen would suck fish onto it like crazy.

I think it is more likely that this would suck fish through the drain screen, perhaps without them slowing down very much either. Maybe get you too if you got too close. :eek1: I would use several outlets to the tank and bigger and/or many more inlets to the pump. Actually when I was thinking along the lines of several very large pumps I was going to build a couple of slotted returns with approx 1 to 2 ft2 flow area to the tank and cycle between them. You should get a lot more real wave action with this and thus better overall turbulence in the tank. From what I have read this is far more desirable than turnover.

heedicus wrote:
The tank started to overflow even though the waterlevel in the overflow was keeping up and was almost at the bottom.

I am not sure I understand this but without seeing the setup but if your overflow runs the length of the tank I would guess that your overflow box might benefit from a couple more drains to the sump or wherever the pump is.

I know you want a lot of flow but I think your flow velocity may be a wee bit on the high side. From what I have read few corals will withstand direct velocities 1-10 to 1/20 of what your 7800 gph pump will put out through a 2" diam pipe. This has got to be putting a little head on that pump.

You might want to calculate the area of your overflow. Measure the height of your overflow slots. Measure the width of an opening. Calculate the area of one then multiply by the number you have. This will probably not give an accurate flow area as the slots are so close together and at your flow velocity there will be turbulence that will affect their maximum flow capability. Cutting out every other one would deifinitely increase the flow area but only by 50% (though it might improve the turbulence problem) and I am not sure how that would affect your surface skimming. Someone smarter than me needs to answer that one.

Build your own formula to calculate what you are doing or use mine but I would hope someone will check my math. Just make sure the units are correct and that you are not combining feet with inches or something like that.

gal/hr * 7.48 ft3/gal *1 hr/3600 sec * 1/(area of inlet or outler in ft2). For those uncomfortable with math: notice how gal/gal cancel and ft3/ft2 => ft and the resulting units are ft/sec.

Gonna be a heck of a "storm" in that tank if it's a 180. :eek:

Charles

[heedicus]

Thanks for all the replies,
I will try to reply to all posts here,


Did you mean 180? If you meant 800 , out of curiosity, what is the dimension of you tank?

It is 4 feet wide, 10 feet long, and three feet tall.

The overflow runs the width of the tank (4 feet), the slots cut in the overflow couldn't keep up with amount of water going into the tank. So the tank started to overflow, even though in the overflow there was more room for water.


The returns are not just a 2 inch pipe, It actually is a two inch pipe that splits into 2 two inch pipes then each of the two inch pipes has 5 outlets dumping into the tank so direct flow shouldnt be a problem, I was worried about on the intake side of the pump. I think I am going to go for 2 2 inch bulkheads that will come together and then feed the pump.
Thanks,
Tren

[pmrogers]

If your teeth are standard 1/4" wide by 1.5" tall you should be able to push about 80gph per linear inch of overflow, or ~3800gph.

For our 120x48x32 I went with 2" tall teeth to get closer to 100gph per linear inch of overflow.

[john rochon]

sounds like your overflow teeth are not cut deep enough to keep up with your pump. dremel them out a bit.

[Shoestring Reefer]

So, is this a used tank, or new?

I agree that bigger teeth would get you more flow; but based on what Paul (pmrogers) posted, you might need gigantic openings to get the flow you need.

7800 gph is 130 gpm. According to Crane 410, 125 gpm through a 2" pipe (schedule 40, assuming steel pipe IDs are the same as PVC) gets you 11.97 feet/second. So 130 gpm will be 12.45 ft/sec. If you went with 1 1/2" pipe, you would be at over 20 ft/sec. IMO that would be fast.

Keeping it down to 10 ft/sec is nice when you're doing stuff like building power plants, but IMO the 2" pipe will be OK. Keep in mind, the closed loop will have little head loss (just some frictional head from the pipe and fittings) so you will have more flow as a closed loop than you did as a return.

chask- it's 7.48 gal/ft3, not 7.48 ft3/gal (which is why a 5-gallon bucket is a bit less than 1 cubic foot). Otherwise the math is probably good. Dividing your answer by (7.48 X 2) equals 13.28 feet/sec. Pretty close to my answer, but Crane 410 uses actual pipe IDs for steel pipe (2" sch 40 pipe = 2.067" ID; again, assuming PVC IDs are the same as steel) :)

[heedicus]

it is a new tank, I am kind of suprised by the lack of flow allowed through the overflows.
but that answers all of my questions thanks for helping out all!
tren

[chask]

Shoestring Reefer wrote:
chask- it's 7.48 gal/ft3, not 7.48 ft3/gal (which is why a 5-gallon bucket is a bit less than 1 cubic foot). Otherwise the math is probably good. Dividing your answer by (7.48 X 2) equals 13.28 feet/sec. Pretty close to my answer, but Crane 410 uses actual pipe IDs for steel pipe (2" sch 40 pipe = 2.067" ID; again, assuming PVC IDs are the same as steel)

Thanks Shoestring Reefer. Sorry about that all. :o In my haze I thought it did not sound right but like I said I was half awake. Been going through a lot of medical tests and just found out this PM it is very likely that I will not die any sooner that I hoped to. Wonderful feeling - maybe that will help with the rest. Of course they use to bleed you and give you mercury so what do they really know? :D

Anyway, with the correction in ft3/gallon the numbers do sound a little better and match yours. 13.28 ft/sec does not sound all that bad. By the time you consider diffusion of the flow after leaving the pipe it would probably be a nice current a short distance away. Delbeek and Spring (I think) had a chart showing typical flow velocities from the outer reef on in to the shore area. I think that this was a fairly moderate to high flow rate but in the range required by some corals to feed. I seem to recall mention of a couple fo species that would not be able to feed much below this. Will check if anyone's interested.

Charles

[Shoestring Reefer]

Originally posted by chask
it did not sound right but like I said I was half awake. Been going through a lot of medical tests and just found out this PM it is very likely that I will not die any sooner that I hoped to. Wow, that's good to hear.