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

[1PoolNoob]

Can someone please help estimate my Total Resistance to Flow (Feet of Head), I'm having a hard time with this.

Pool specs:
In-ground 30,000 Liters / 7800 Gallons
Piping diameter: 1.5 inch
Distance from skimmer to pump location: 45 feet Horizontal and 6.5 feet Vertical
Has 1-skimmer and 2-returns in the pool
Sand filter: 17-inch

Any more info needed?

[mas985]

I can help but I have to ask what is your objective and why do you need to know the head loss?


As for additional information:

Pump make/model

Filter make/model

Backwash valve size

Current filter pressure

Picture of the pad might be helpful too

[1PoolNoob]

I can help but I have to ask what is your objective and why do you need to know the head loss?


As for additional information:

Pump make/model

Filter make/model

Backwash valve size

Current filter pressure

Picture of the pad might be helpful too

Awesome thanks a lot. My current pump is all but dead (leaking etc.) and I am looking at replacing it with a Hayward Super Pump 3/4 hp (Model: SP2605X7A).

The issue is that the old pump is about 30 years old and pumps these days put out a lot more GPM for the same HP than they used to and I am concerned that the new pump may be too powerful for my setup. I was unable to find any specs for the current pump due to it's age for comparison purposes (I called Pentair, which purchased Pac-Fab, to see if they had any data on it, but their records did no go back that far).

I figure if I can get a reasonable estimation of what the Total Feet of Head is, I can look at the performance curve and see what the pump's resulting flow rate will be and whether that will be too much, or acceptable for my system. The last thing I want is to install a new pump, only to have something else break because it's too powerful.

I remeasured/calculated the pool size and it is closer to 8400 Gallons (not a whole lot different than before)

Setup:


Current Pump model:


Specs on motor of pump:


Sandfilter Specs (it is a 17-inch I believe, and old as well): (note I am in Canada If things are slightly different)


Current Filter pressure is around 13 psi after a backwash and 15 psi when its getting full.

Performance Curve for the new Hayward Super Pump:

[mas985]

Best I can tell, the current pump is producing around 52 GPM @ 54' of head and a new 3/4 HP Superpump would produce around 32 GPM @ 21' of head (note head loss is not a constant and depends upon flow rate). The lower flow rate is because the current pump is a full rated pump and the Superpump is an up rated pump.

Also, sand filter are much more robust than most filters so although your current pump is exceeding the recommendations, it is probably not enough to really damage the filter. However, the filter is very small and you might want to up size that at some point.

[mas985]

Sorry correction, the new Superpump would have an operating point around 44 GPM @ 39' of head. I used the wrong pump above.

[1PoolNoob]

Best I can tell, the current pump is producing around 52 GPM @ 54' of head and a new 3/4 HP Superpump would produce around 32 GPM @ 21' of head (note head loss is not a constant and depends upon flow rate). The lower flow rate is because the current pump is a full rated pump and the Superpump is an up rated pump.

Also, sand filter are much more robust than most filters so although your current pump is exceeding the recommendations, it is probably not enough to really damage the filter. However, the filter is very small and you might want to up size that at some point.

Sorry correction, the new Superpump would have an operating point around 44 GPM @ 39' of head. I used the wrong pump above.

Would you mind explaining a bit how you came up with those numbers, more specifically the GPM for the current pump and the feet of head for both...

As far as I can tell, the sand filter has a max flow rate of 20 GPM, if it was currently at 52 GPM wouldn't that be kind of through the roof? And also can't 1.5" piping only safely handle around 47 GPM?

Thanks again for your help.