# How to cut a pipe such that water comes out evenly across the length?

I am trying to build a wetland filter for a pond. Basically, you dig a big hole, fill it with rocks (large at bottom, small at the top), and pump water deep under these rocks, so the water slowly trickles upwards. My main problem is finding a way to make sure the water from the pond is pumped underneath the wetland filter, in an equally distributed amount. I can't have the water pouring underneath in one or two spots, it should be equally distributed.

                                                                   X
x |  X <-- flowers
()/
|~~~~~~~~~~~~~~~~~~~~~~||~~~~~~~~~~~~~~~~~|
|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| |................(wetland filter).........|
|                   (pond)                | |ooooooooooooooooooooooooooooooooooooooooo|
|                                         | |                                         |
|     <-|-|-|-<                           | |                                         |
|_________________________________________| |_________________________________________|


A big pump is dropped in the pond, and a pipe leads it underground under the wetland filter. Its basically a space with big rocks, with water in between.

  ___    water flow--->              hole
[   ]_________                       |
[   ]_________\                      V
[   ]         \\______o____o____o____o____o___o____o____o___o___o___
/     \         \____________________________________________________] <--cap on end
^                          ^
|                          |
pump                      2" diameter PVC pipe
`

I need to get the water dispersed evenly underneath the wetland filter area. Some other people recommended using PVC pipe, and simply drilling holes in it. The water should go out through the holes. But those suggesting had a 5 ft wide wetland filter, mine is 150 ft long, so I don't know if that solution scales.

My concern, because I have a larger-than-typical design, with the pipe being almost 150 feet long to reach all of the bog, how do I insure the water is evenly distributed to each of the holes?

Will the water pressure equalize and cause the same amount of water to go out of each hole? Does that require carefully making sure the total accumulated size of all of the holes equals the flow rate?

Do I need to make the holes incrementally get bigger towards the end of the pipe? If so, how do I scale the holes along the distance?

• +1 for the ASCII art. That must have taken a looong time. Feb 4, 2021 at 18:41
• Do you need to have equal pressure or equal flow? Do you have any idea about the diameter of the pipe and the pump characteristics (flow, head pressure)? Feb 4, 2021 at 18:45
• I don't understand the difference between equal pressure and equal flow. I want the water to come out at the end of the pipe the same as it comes out the start of the pipe. Feb 4, 2021 at 18:54
• The pump manufacturer recommends 2" pipe or larger. I can scale up to 4" for instance if that helps. Specs: 4,000 GPH, Max Head Height: 21". Note sure if there are other specs that are useful. Feb 4, 2021 at 18:55
• The difference in equal pressure or equal flow is the following, if you have the equal pressure you can have different flow rate if the diameter of the hole is different. And in general (e.g .for a level, straight pipe) you shouldn't get much pressure difference between the first and the last hole, especially given that you have more that 1Gallon per sec, going through a 2'' pipe, provided the exit holes are small enough. Feb 4, 2021 at 19:31