Flow rate being restricted by hose size

[dinm]

I'd received a 2000gph pump a day ago, when I tested it with a 19mm hose the flow was really bad. Now initially I was stunned and thought it might be a leak or something, but it would appear that the 19mm size is restricting the flow a lot. Now my question is how much flow can really be blocked by using a small hose? I assume it must be a lot because I have currently a 660gph pump and this 2000gph, and for the life of me I cannot see the difference with my eyes between them, both use the same hose.

It came to my attention then that I am using the smallest possible size on this new pump, and then I read that I should use the biggest size possible and that using smaller sizes can make the pump work harder than it would normally. I am now gonna upgrade to 32-38mm size, but I am wondering, how much flow can actually be lost this way? It seems a lot can be lost because I don't see the difference between 660 and 2000 this way.

 

[JRS]

You are correct, can make a big difference. You are going to have more back pressure/resistance the smaller the pipe.

Sometimes very similar pumps can have differences in the impellers or wattage that can matter, everything else being the same. Note the different flows under the Specifications tab for the same outlet sizes:

Pondmaster Pond-Mag Magnetic Drive Water Pumps

PONDMASTER POND-MAG® 250 to 3600 SERIES PUMPS have been designed to handle virtually any application where water has to be moved. They've been fulfilling the needs of professionals and consumers for decades with quiet, efficient and reliable 24/7 performance. They feature a magnet impeller...

dannermfg.com

Pipe size, type and configuration (elbows and bends) and also be a factor.

For example, on the yellow chart below with the same pressure for all your pipe sizes flow rate changes a lot: 19mm(.75inch) 8.9 gallons per minute; 32mm(1.25inch) 38 gpm and 38mm(1.5") goes to 66 gpm.

From this site: https://wcponline.com/2013/02/03/hydrodynamic-design-part-2-flows-pipe/

 

[dinm]

You are correct, can make a big difference. You are going to have more back pressure/resistance the smaller the pipe.

Sometimes very similar pumps can have differences in the impellers or wattage that can matter, everything else being the same. Note the different flows under the Specifications tab for the same outlet sizes:

Pondmaster Pond-Mag Magnetic Drive Water Pumps

PONDMASTER POND-MAG® 250 to 3600 SERIES PUMPS have been designed to handle virtually any application where water has to be moved. They've been fulfilling the needs of professionals and consumers for decades with quiet, efficient and reliable 24/7 performance. They feature a magnet impeller...

dannermfg.com

Pipe size, type and configuration (elbows and bends) and also be a factor.

For example, on the yellow chart below with the same pressure for all your pipe sizes flow rate changes a lot: 19mm(.75inch) 8.9 gallons per minute; 32mm(1.25inch) 38 gpm and 38mm(1.5") goes to 66 gpm.

From this site: https://wcponline.com/2013/02/03/hydrodynamic-design-part-2-flows-pipe/

That seems like a lot of difference. No wonder I cant notice the difference between 660gph and 2000gph. Tomorrow I receive the 32mm so I shall see how much difference it makes in person.