Reef Hydraulics & Fluid Mechanics

[Pat H.]

Thanks Matt for a great presentation! I found it very helpful and it got me thinking about my plumbing...again.

I have two drains in my system. One at each end of an 8' tank. First, the water flows through a toothed overflow (12"x5") then a Durso standpipe (1 1/2" dia). Then through 1 1/2" flexi tubing to my sump.
The difference between these drains is, one sides flexi tubing is about 2' long and the other 5' long.

What is happening is the longer side seems to be doing most of the work, by about 3 to 1. I'm running an Iwaki MD55RLT for my return(i'm guessing with 4' head, around 900 gph ??). The tank has been running like this for about 7 months without a problem, but i'm curious why this is happening.

I'm very interested in your reply.
Thanks again, Patrick

 

[NateHanson]

Could the tank be very slightly out of level Patrick? Over 8 feet that could make a significant difference in the height of the water over the comb.

 

[Pat H.]

Actually Nate, you may have something there! The tank is out of level about 3/32" from side to side. And the deeper end is the end that gets more flow. I do have 8 adjustable leveling feet under the stand, but i'm very hesitant to use them with the tank full (probably weighs close to 2 tons). I wonder if that small amount could be the difference?

 

[Matt L.]

I believe Nate is right, and yes, such a small difference in elevation would matter. Aside from leveling the stand or raising the lower of the two overflow weirs, there is nothing that can be done to make the flow between the two sides more equal. When having an overflow weir, it is always best to try and have the weir adjustable to deal with minor discrepancies in flow that arise,

Matt

 

[Jim Tansey]

If the overflowes are the finger type with much of it submerged I don't think 3/32 would make much of a difference.

Jim

 

[Pat H.]

Thanks everyone. It seems that is the answer. I must have made a 1/8" error when making my overflows (yes Jim, the finger type) making that side even lower . Almost 1/4" total (when added to the 3/32"). I wish I made them adjustable, but I was in a hurry...
Can't believe I never noticed before.

 

[NateHanson]

Should be easy to fix Patrick. Just stick a piece of acrylic to the inside of the overflow comb, blocking the bottom 7/32" of the comb on the low side.

 

[Pat H.]

Yeah Nate, I think i'll try that. I'll just clamp it with a couple of those plastic squeeze clamps to test it. If it works, I'll glue them in place. Thanks everyone! I thought I had a plumbing mystery to figure out. Sorry it was a dud

-Patrick

 

[~Flighty~]

Better late than never- I just now got around to reading this. Great presentation, I should have read it ealier. I think it answered my argument with Eliot about wether or not a really long ro/di output line adds a lot of back presure on the unit. It doesn't because the water is going too slowly for frictional losses to be signifigant even over 50 ft of line. right?

 

[marco67]

Cindy,
I'm even a step behind that...I just now found the thread and haven't had a chance to read the presentation yet. I sure wish I could have attended!
BTW thanks for bringing it to the surface !

 

[Scuba_Dave]

Almost lost me on slide 3
Nice to have this brought back up
Nice job Matt

 

[S Hunter]

Links are gone Dead thread!!!

 

[~Flighty~]

Good point. Can we get those up somewhere on our site, Matt?

 

[delta]

Please find below the recommended flow rates for each standard line size based on the true inner diameter of Schedule 40 pipe.

Use This Diameter:       Between These Flows:      And for no more than:
         0.5                 170 - 284                       398
         0.75                299 - 499                       698
         1                   485 - 808                       1131
         1.25                839 - 1398                      1958
         1.5                 1142 - 1904                     2665
         2                   1882 - 3137                     4392
         3                   4147 - 6912                     9677
         4                   7142 - 11903                    16664
         6                   16207 - 27012                   37817

Notes:
1. All flows are in gallons per hour (gph)
2. These recommended flow values are for closed channel flow only! These do not apply to your D'Urso standpipe or any other open channel return.

Matt

Found the Pipe sizing table

 

[S Hunter]

Thanks Greg

 

[delta]

I found the actual pipe tables Matt Posted
http://www.bostonreefers.org/forums/attachment.php?attachmentid=27604&d=1177805569

 

[mano1192]

How many tank changes per hour should you try to achieve? I have a 92g Im designing now, I will be using a open loop system w/ 2 pumps in the tank on emergency power. Im tryin to size the pipe and pump but need to know what my water turnover rate should be to properly size it up. As always thatnks for the help!

 

[Matt L.]

Hey guys. Sorry about the pipe tables.

The pipe tables were hosted on a University account that was cleared when I transitioned from student to faculty.

Can anyone host these files in a more permanent location?

Matt

 

[smithcreek]

Is the presentation document hosted anywhere? I can host them if not.
Dave

 

[Yaktop]

is this available anywhere ?