if you put 1 pipe between 2 pumps, you get 6000 liquid per second.
2 pipes between 2 pumps is 3000 liquid per second.
3 pipes = 2250 and so on, longer sections, lower liquid speed (flow rate or ''pressure'' for the factorio devs who do not understand what the word ''pressure'' means, they obviously don't understand how pipes work in real life either)

anyway, what is the speed for these pipes? it says it's 4 times faster... okay, so take my numbers and multiply by 4? This mod still suffers from the same flaw of longer pipes = slower liquid flow speed? What are the numbers? Your mod doesn't show it when hovering your mouse over a pipe, does it? So how am I supposed to know what the limit is? How will I know when I need to put a pump?

First of all we need to understand how work factorio fluid engine ("work" is a euphemism but let's do this):

Each entity have a fluidbox, and "ports" some connections. Each connection could be 3 type "input", "output" or both, we need this to understand that consumer like chemical plant and assembler are in input connections, pump are in output, and pipes and storage tanks are in input/output mode, so what's imply this?

Each fluidbox (that have more fluid of one neighbor) will share liquids to the output or input/output connections, but with what equation?
OFF = total fluid inside fluidbox sender
IFF = total fluid inside fluidbox that receive the input
Throughput = |OFF-IFF|/2 <-- the difference from the two fluidboxes

This means that throughput of something is related to the actual max that the OFF can store inside, and release it.
For get the best throughput from an entity must be "full" or his connections must have a "full throughput" for give the "max throughput", so if u provide two pipes with one duct, the duct must have a throughput in input equal to the max throughput of two pipes, otherwise u got a bottle neck.
For prove this theory try to fill a storage tank with a pump, in one case with a full storage tank connected to the pump, in the second case with a pipe that is before the full storage tank, and u will see that if the pump have a bigger fluidbox behind give a bigger throughput.

Potentially, ducts have the throughput of 4 pipes because have a max fluidbox 4 time bigger and the pump of ducts is 4 time powerful.

About the problem of length, factorio fluid engine force player to build a short fluid network, because if u will think a moment about that equation u will understand that more is the fluidboxes more is the time needed to share fluids, less is the difference between entity, minor is the throughput, and if we suppose a situation where consumer request > throughput, no accumulations or stable fluid quantity inside -> low throughput.
Ducts help alot when normal pipes haven't a good flow in situation like, many consumer, many pipes, for avoid spaghetti of pipes.

PS: place pump in a section of the network will give a "better" flow because the fluid can't go back, so returning to the equation, the nodes beyond the pump have more fluid because will not share it with other before and bla bla...

I think I understand the logic behind your mod then, and it says the flow of liquid is hard coded into factorio? I was hoping of a mod that would keep the flow speed of a pipe, no matter how long the pipe is (because normally longer pipe = slow liquid speed).

But you got around this by making these big sections, that are made up of double pipes, and the long length of underground pipes (and underground pipes ''teleport'' liquid, they don't move liquid) so in a straight line it's very effective.

I don't think the big liquid capacity on your mod makes a big difference (vanilla pipes have 100 liquid capacity, your ducts have about 1500)... capacity and speed are different things.

Btw, are you aware that you can use underground ducts as splitters in your mod? 1 splits into 2, then 2 into 3 etc., that's interesting. And also, small pipes can connect directly to 1 big duct

tl;dr I'm getting the same exact liquid flow speed with your mod pipes. Your mod pipes help only when using pipes over very very long distances

Thanks for the quick and long reply

As I said, in factorio capacity and flow is directect influenced, no mod can change this (because is hard coded into factorio base game, mods must adapt all fluid things on this), u are free to test and delete this mod if isn't ur promised savior.

Theoretically, u could not use the underground part as a splitter if u follow the "logic", if players want cheat, who cares, is their choice and I don't want say to other players how play, u could imagine as underground splitter if u want, I put constraint only on some things.

The mod is an tool, is the player that must do the rest.

ok thanks for the info.

But you can split pipes, it is possible, look: https://i.ibb.co/kmKJ6p0/3397.jpg

In fact I said "theoretically" not "practically", and too: "if players want cheat, who cares, is their choice and I don't want say to other players how play". If ur repetition is for say: "It's a bug because... must be fixed", for me is not a bug.

ah I get what you mean, sorry. Yeah you're right, it's cheating.