Can someone help estimate my Total Resistance to Flow (Feet of Head)

[mas985]

The filter has a recommended flow rate of 20 GPM. There is no true maximum but there can be a point where it damages the filter. However, sand filters are fairly robust and it is difficult to damage them but it does happen once in a while. Also, with pipe, there is no maximum either. There is only increasing head loss with flow rate. It doesn't really make it unsafe but it does make in inefficient. The limits that you read about are actually recommendations to minimize head loss and water hammer but there are no fundamental limits.

As for the methods that I use to determine head loss, it is a little complicated but it is a two step process. The filter pressure gives you the head loss from that point out of the returns:

Return dynamic head loss = 13 PSI * 2.31 + 9.5 = 39.53' of head

9.5' is the height of the filter gauge above the water level.

The suction side is a little more difficult because you don't have a suction measurement so for that, I calculate the equivalent plumbing curve based upon the description of the plumbing you gave me. I then use the pump's head curve to find the operating point.

I have a spreadsheet that does the calculations in my signature under "Energy Efficient Swimming Pools".