4 inch flow rate [Archive]

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steveandlou

can anyone tell me the max gravity flow rate of a 4 inch pipe
the pipe will be 20 ft long and have a fall of 24 inches

oh and im in england so english gallons would be great

thanks for your help on this

steve

boggen

gallons US per hour is min suggested
as far as MAX gallons US per hour. that all depends. on the acceptable "draw down level"

what are you trying to do? (what connects to what) diagram?

below link can help ya convert between flow rates.
http://www.onlineconversion.com/flow_rate_volume.htm

steveandlou

this is for my new filter that i had built there is a post on it below somewhere showing filter

GloriaL

Ryan I think that he is asking what is the most water that WILL go through a four inch pipe of twenty feet in length with a twenty four inch drop in elevation from one end to the other.
This is information I have also had a hard time finding . It seems people want to come up with a single number for a certain diameter pipe w/o taking into account the elevation change. It is pretty obvious that the flow will be much faster through a 100 foot four inch pipe that is oriented vertically than through a 100 foot length of four inch pipe that only has one inch of elevation change from one end to the other. Then you have to add in the head generated by your fittings, etc.

mtsklar

For 20 feet of pipe and 24 inches of drop a 4" pipe will flow 14,000 GPH with a water velocity of 6 feet per sec.

mtsklar

Ryan,
What is your source on the min. suggested flow rate?



gallons US per hour is min suggested
as far as MAX gallons US per hour. that all depends. on the acceptable "draw down level"

what are you trying to do? (what connects to what) diagram?

below link can help ya convert between flow rates.
http://www.onlineconversion.com/flow_rate_volume.htm

APOLONASGR36

For 20 feet of pipe and 24 inches of drop a 4" pipe will flow 14,000 GPH with a water velocity of 6 feet per sec.

At least that. And you have another 20''-24 '' extra drop inside your container. As I said to you in your other thread you will not be able to overflow your container with an open 4'' inch pipe as gravity return back to your pond.

APOLONASGR36

Ryan,
What is your source on the min. suggested flow rate?

Matt he is talking 4'' bottom drain minimum flow for appropriate water velocity so you do not accumulate settlement of debris.

steveandlou

thanks for the replies guys

its just some think itll overflow before it empties im sure itll be fine

i found this sitye which explained it a bit for me

http://flexpvc.com/WaterFlowBasedOnPipeSize.shtml

boggen

Ryan,
What is your source on the min. suggested flow rate?

min flow for a 4" pipe is based on velocity of 1 fps.

http://www.worldwidekoiclub.org/index.php?option=com_content&task=view&id=88&Itemid=60
or
www.worldwidekoiclub.org -> pond building info -> calcs -> advance pipe sizing calc -> just click ""calc"" button

the calc only denotes velocity, and as a quick aid shows P or G for pressurized or gravity flow of water.

ok well actual calc denotes 1.06 Feet per second velocity = gph in a 4" pipe. but close enough. as min gph.

longer pipe runs, use of sharp 90's and extra fittings in the pipe line between bottom drain and first filter the pipe run goes to. can cause extra clogging. and / or may require a higher min velocity above 1 feet per second.

mtsklar

Ryan,
Well this is off topic a little however for any one that is reading your post or may in the future use the information.
At 1 foot per sec in a 4 inch pipe there will be settling slit in the pipe. Flow rate in a 4 inch pipe needs to be 3 feet per second to prevent accumulating slit in the pipe.

3 feet per second requires about gph which is about double what most people run. To overcome the slit build up it is a good idea to flush the bottom drain lines as a part of regular filter cleaning.

What flow rate do you run on your pond? How does that work for you?


min flow for a 4" pipe is based on velocity of 1 fps.

http://www.worldwidekoiclub.org/index.php?option=com_content&task=view&id=88&Itemid=60
or
www.worldwidekoiclub.org -> pond building info -> calcs -> advance pipe sizing calc -> just click ""calc"" button

the calc only denotes velocity, and as a quick aid shows P or G for pressurized or gravity flow of water.

ok well actual calc denotes 1.06 Feet per second velocity = gph in a 4" pipe. but close enough. as min gph.

longer pipe runs, use of sharp 90's and extra fittings in the pipe line between bottom drain and first filter the pipe run goes to. can cause extra clogging. and / or may require a higher min velocity above 1 feet per second.

GloriaL

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Does anybody know where I can find a chart that depicts STRICTLY gravity flow through 100 feet of pvc pipe by size of pipe AND per foot of elevation drop? Then maybe one for max pumped flow per 100 feet.
I get confused by different people stating that you can expect to get "x"flow thru a 4" bottom drain. I have no idea where that number comes from. Is it the restriction thru the bottom drain itself? If so are there charts for each brand bottom drain by the amount the drain is open? The implication with most of these statements is that the restriction is the size of the pipe. But maybe I have misunderstood all this time and the main determinent of flow through the bottom drain is the bottom drain itself?:confused::confused:

icu2

Here's one I use all the time... it's been pretty accurate. Came from this site too, but now
I can't remember where! But RyanS should get credit for it. :wtg:

As far as I can tell, it assumes zero head from fittings... but just how much is possible. And
it shows how the height difference affects potential flow rates.

GloriaL

Does anybody have any info on flow rate through various brands of bottom drains?

koiman

Does anybody have any info on flow rate through various brands of bottom drains?

Gloria

This could be based on the amount of vertical spacing provided between the floor of the pond and the "dome". This has a lot to do with not only the "skimming" action of the drain's velocity, but also the flow rate available. Most all drains outlet ports are horizontally located and are full size of 3" or 4" so that doesn't really restrict the flow and the above chart is useable. Personally, when installing the domes on the drains on a pond, we like to use 5/8" or better, 3/4" from pond floor to the bottom of the dome lip.

Mike

GloriaL

Gloria

This could be based on the amount of vertical spacing provided between the floor of the pond and the "dome". This has a lot to do with not only the "skimming" action of the drain's velocity, but also the flow rate available. Most all drains outlet ports are horizontally located and are full size of 3" or 4" so that doesn't really restrict the flow and the above chart is useable. Personally, when installing the domes on the drains on a pond, we like to use 5/8" or better, 3/4" from pond floor to the bottom of the dome lip.

Mike

Thanks, but I guess that is bye-bye to the baby fishes!! Seriously at what gap does the bottom drain become the limiting factor?

Pond James_Pond

When the area of the opening of the bottom drain dome is less than the area of the bottom drain pipe.

GloriaL

When the area of the opening of the bottom drain dome is less than the area of the bottom drain pipe.

R I I I GHT! Which will depend on the diameter/circumference of the lid and the gap... So anybody know what that is for various commercial BD's?

Zac Penn

I just want to clear something up here to make sure everyone is still on the same page. When we are talking about elevation change of the pipe vs head height I can get confused as to what people are saying and what they are intending to say.

If SteveandLou (sp?) is actually just talking about the elevation change from one end of the return pipe compared to the other end, then there is a major variable being left out here...............Does the 4" pipe ever go below water level during the 20' length of pipe, and 20" elevation change? If it does, then you CAN NOT account for any of the elevation change that occurs below water level. The only thing that matters is the water height inside your filter container, compared to the water height inside the pond.

I know it doesn't sound right, but if you have a single container with two exit ports, two identical sized pipes with the same number and style of fittings, same length of pipe, and returning to the same body of water...............Then both of those pipe will flow the same amount of water even if one is 2" below the pond surface and the other is 20' below the pond surface. The back pressure exerted on the return pipe will be the same!

Zac

Zac Penn

When the area of the opening of the bottom drain dome is less than the area of the bottom drain pipe.

This is true to an extent, but you need to throw in something like a 10% friction loss caused by the extra surface area of the bottom drain cover and pond bottom. The water trying to go under the BD dome cover will have a restriction to flow....So lets consider this situation....

4" BD suction pipe has ID of 4" so 3.14 x 2^2 = 12.56 sq in

hypothetical BD dome cover has a 16" diameter so it has a circumference of 16 x 3.14 = 50.24"

To get the same open area as a 4" pipe you would use this equation... 12.56/50.24 = .25" (gap between the bottom drain dome cover and pond floor)

Just because with a 1/4" gap between the BD and pond floor gives you the same open area as the 4" pipe the friction between the dome and pond floor will reduce the amount of water flowing through it, so this is where the 10% friction loss (made up percentage by me (Could be closer to 5%)) would come into play.

So if our calculations say a .25" gap is required with a 10% friction loss you should actually make your gap... .25" x 1.1 = .275"..... .275" x 50.24 = 13.82" open area!

Zac

Pond James_Pond

Nice. I stated the fact, but I was waiting for a math wiz to chime in and draw out the formula.

Well done, Zac.

This should be in the FAQ!!

steve

Zac Penn

I wish I could really know what the friction loss percentage would be in these kinds of situations, but for now I just use 10% on my designs.

Pond James_Pond

What do the friction loss charts say for the smallest pipe diameter? Is that what you're basing your educated guess on? If there was a chart for a 1/4" pipe, that's the number to use for our velocity range.

steve

wputnam

Nice work on the dome gap Zac, but the pond bottom surface on most ponds varies around the bottom drain and often creates a smaller gap which then increase the water velocity and friction passing through the gap...
It has happened to customers that have a 1/2" gap in the dome to have the DOME get sucked flat... So we usually recommend having a gap of 3/4" to 1" ....

A note on the pipe flow and elevation change... ONE factor that increases the flow is any build up of water higher then the entry to the 4" pipe... Atmospheric pressure for every inch of water above dramatically increases that flow rate... Just my 2 cents...

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