Yeah I was wondering about using multiple D5 pumps when I was first setting this up as well...I really did want an iwaki but they didn't have any availible locally
That said, two D5s won't perform anywhere close to as good as a single iwaki...as Nubius mentioned, it isn't 12ft + 12ft since there are certain factors you have to put into consideration
Basic physics, if you put two D5s directly beside each other in a series they're going to bottleneck each other in a sense...the second D5 isn't really speeding up the water any faster than the current flow rate as it can't pump water any faster than the first D5 in the first place, so all it's doing is basically "amplifying" the flow back up to what it was when the water first comes out of the first D5
The other method I came up with was using a Y splitter and having the two D5s in parallel beside each other, and then reconnect using another Y splitter...from what I gathered at XS the pumps actually end up not having enough water to draw from to benefit this setup, and furthermore, when the water comes back through the Y splitter the water from each tube is going to collide and create some more resistance
So basically the best way to benefit from two pumps is to run seperate loops, but it's better to just have one really powerful pump...I'm no expert and have little experience with water so I'm very much a noob on this subject but I know maxxxracer and several others have tested numerous configurations so they would be your best bet for finding answers
That said, two D5s won't perform anywhere close to as good as a single iwaki...as Nubius mentioned, it isn't 12ft + 12ft since there are certain factors you have to put into consideration
Basic physics, if you put two D5s directly beside each other in a series they're going to bottleneck each other in a sense...the second D5 isn't really speeding up the water any faster than the current flow rate as it can't pump water any faster than the first D5 in the first place, so all it's doing is basically "amplifying" the flow back up to what it was when the water first comes out of the first D5
The other method I came up with was using a Y splitter and having the two D5s in parallel beside each other, and then reconnect using another Y splitter...from what I gathered at XS the pumps actually end up not having enough water to draw from to benefit this setup, and furthermore, when the water comes back through the Y splitter the water from each tube is going to collide and create some more resistance
So basically the best way to benefit from two pumps is to run seperate loops, but it's better to just have one really powerful pump...I'm no expert and have little experience with water so I'm very much a noob on this subject but I know maxxxracer and several others have tested numerous configurations so they would be your best bet for finding answers