[banditpowdercoat]

But back to the basic question. Does head pressure change at the pump, when using larger diameter pipes for tank return.

NO, it remains the same. The pressure the pump see's is equivalent to the weight of water equaling the volume of a pipe the same diameter as the pump outlet, times the head height.

Now as far as friction losses, they are regardless of head height. Friction losses will happen on horizontal runs as well as vertical. If said pump was loosing flow (GPH) due to frictional losses, then yes, upping pipe size can gain back some lost GPH.

Heres a chart comparing firehose sizes and friction losses per 100' of hose. Distance and flow determine friction losses, not head height



Losses in PSI of firehose per GPM flow @ 100 PSI pump pressure

1.5" diameter
GPM/ PSI Loss

50 6.3
100 25
150 56.3

2" diameter

50 1.7
100 6.6
150 14.8
200 26.3
250 41.1
300 59.2

2.5" diameter

150 4.9
200 8.7
250 13.5
300 19.5

And for elevation, add 0.5 PSI for each foot