15 replies to this topic

[sumthinfishys]

Gravity and pipe size???

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How gallons per hour through a 3 inch drain? (pipe)
How many through a 4 inch drain? (pipe)

Mike C

[dcny]

Gravity and pipe size???

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How gallons per hour through a 3 inch drain? (pipe)
How many through a 4 inch drain? (pipe)

Mike C

with a 1" drop you get a little over 3000gph thru 4" and a little over 1500gph thru a 3"...
with a 2" drop you get a little over 6000gph thru 4" and a little over 3000gph thru a 3"...
etc...

[sumthinfishys]

with a 1" drop you get a little over 3000gph thru 4" and a little over 1500gph thru a 3"...
with a 2" drop you get a little over 6000gph thru 4" and a little over 3000gph thru a 3"...
etc...

What do you mean by a 1 and 2 inch drop? The distance in the bottom drain? The drains I will be using are 10 inches deep?

Mike C

[dcny]

What do you mean by a 1 and 2 inch drop? The distance in the bottom drain? The drains I will be using are 10 inches deep?

Mike C

the drop refers to the level of one container to the next.

so if you have a settlement chamber connected to your mechanical filter chamber via a 4" pipe then you will flow about 3000gph if the height difference is 1", i.e. the mechanical filter chamber will be 1" lower than the settlement chamber.

settlement and mechanical chambers were just an example. it can just as easily be your pond and settlement or any two containers connected by a pipe.

Attached Files

•  drawdown.jpg   18.95K   27 downloads

[MCA]

like Dan is pointing out...the "engine" for moving the water is gravity. It drives water to seek its own level. So the more water difference between two contains the greater the pressure to equal those levels. The rate of flow will therefore be driven by

difference is water level
resistance to flow (mostly pipe size)

small flow:
minimum difference in water levels and
small connecting pipe

medium flow:
large difference in water levels but with small connecting pipe or,
small difference in water levels but with large connecting pipe

big flow:
large difference in water levels and
large connecting pipe

[bubba]

is this a correct interpretation ?

if all the pipe i the diagrame is 4 inch and i hooked a 3000 gph pump on that system i could expect a 1 inch "drawdown " in the first tank[closest to the pond] 2 inches in midddle tank and 3 inches in the last tank closest to the pump

with a 6000GPH pump 2 4 and 6 inch drawdowns ?

what about a 12000 GPH pump ?


is it proper to think of the inches of drop you refer to as inches of head ?


just thinking of this summers retrofit

[MCA]

remember the pipe is not the only resistance source. much of the resistance is the media....type and qualtity. That is what is nice about fluid beds....the moving media will offer less resistance that a stack of beads or slab of matting.

[dcny]

is this a correct interpretation ?

if all the pipe i the diagrame is 4 inch and i hooked a 3000 gph pump on that system i could expect a 1 inch "drawdown " in the first tank[closest to the pond] 2 inches in midddle tank and 3 inches in the last tank closest to the pump

with a 6000GPH pump 2 4 and 6 inch drawdowns ?

what about a 12000 GPH pump ?
is it proper to think of the inches of drop you refer to as inches of head ?
just thinking of this summers retrofit

Yup, that's pretty much it. As you probably guessed 12,000gph will 4", 8" and 12" drawdowns. Clearly, you wouldn't want that large of a drawdown. That's why you have to be careful about having too many chambers in series.

I'm not sure of the answer to the drawdown vs head question. We need someone more knowledgeable to tell us. I would guess that they are similar. Both are related to friction loss created by the pipe, bends, etc. Drawdown is normally used in gravity flow situations. Head is normally used in pump fed situations.

[sumthinfishys]

I was hoping to run 3 inch pipe to each nexus due to 4 inch ball valves costing $253 each and three inch ball valves only costing $143 each. If I run 4 inch pipe than reduce it before the valves will it give me the 3200 gal that nexus can take? Or should I just pony up the cash and get 4 inch ball valves? 2 of them for $500 (ouch)

Mike C

Edited by sumthinfishys, 08 February 2007 - 12:07 PM.

[dcny]

I was hoping to run 3 inch pipe to each nexus due to 4 inch ball valves costing $253 each and three inch ball valves only costing $143 each. If I run 4 inch pipe than reduce it before the valves will it give me the 3200 gal that nexus can take? Or should I just pony up the cash and get 4 inch ball valves? 2 of them for $500 (ouch)

Mike C

To save some money use a knife valve. For that application, you just care about on/off so a knife valve should work. Ball valves are more critical if you need to throttle the flow.

A 4" knife valve only costs $57.95 from Fancy Koi Outlet. http://www.fancykoio...y/gatevalve.htm.

plus they're one of our sponsors

[sumthinfishys]

Knife valves always fail, I need sumthin that won't leak. Ball valves are the way to go.

Mike C

[MCA]

I always use knife valves on BDs to filters and on skimmer feed to pump. Never had leaks or needed to replace seals. guess I am lucky

I did have to take a knife apart....someone put a floating duck in the skimmer ended up trapped inside a 3" knife valve. Easy to undo the 4 bolts, remove and dispose of that damn duck, and put the valve back together.

[schildkoi]

Mike,
Use 4" pipe and 4" ball valves.

Steve

[slackjeep]

I have a hard time with plumbing issues so forgive my stupid question. In using 4" pipe at some point you need to go down to 2" on the pump. How does this affect flow and draw down or does it?

Example: 4" to chamber 1, 4" from chamber 1 to chamber 2, what size out chamber 2 to 2" pump intake?

[schildkoi]

I have a hard time with plumbing issues so forgive my stupid question. In using 4" pipe at some point you need to go down to 2" on the pump. How does this affect flow and draw down or does it?

Example: 4" to chamber 1, 4" from chamber 1 to chamber 2, what size out chamber 2 to 2" pump intake?

I like to run the 4" out of the last chamber to just before the pump. I put a 3-way valve before and after the pump. The other 2" on the pump intake side goes back to the 4 inch line before the 4" ball valve. this allows for the pond to be pumped dry if ever necessary (direct draw). the 3-way on the dischrge side goes directly to waste.(and of course the opther back to the pond.

Attached Files

•  Nexus_plumbing.JPG   22.23K   4 downloads
•  7.bmp   1.29MB   58 downloads

[slackjeep]

just found this again. Thanks Steve. That really helps a lot!