Hi,

I am having a gunite pool installed soon. The pool is 30'x24' but if you look at the picture you'll see that it's actually a much smaller pool than those numbers make it look like. It also has a beach entry for the first step which is rather large. Total surface area is around 470 sq ft. Depth will vary from 3.5ft to 6ft. My designer estimated the pool to be 22,000 gallons but I just can't come up with that number any way I try. Actually it seems like he used an ellipse approximation of 30x24ft and used an average depth of 4.75ft ((3.5+6)/2). With this calculation I get 20,000 gallons but the ellipse area would end up being 565 sq ft and I already know that the pool is nowhere near that.

Long story short, based on my calculations I am estimating between 13,000 and 17,000 gallons (I am thinking it'll be a lot closer to 13,000 than 17,000 though).

The designer added a 1.5hp pump to my contract but I think it is an overkill for my application. They are installing 2" drain, skimmer (2 skimmers) and return lines (the return line get reduced to 4 1.5" returns). My equipment will be probably about 50ft away from the pool. I don't know what my total dynamic head is going to be but I can't see it being excessive. I'm going to have a salt water system (so the salt generator will add some dynamic head) and I will have a Jandy DE 60 sq ft filter which is capable of 120GPM flow if needed.

OK, so the question is: why would I want a 1.5hp pump? In worst case scenario my pool is 17,000 gallons and if I want to turn the water around in 6 hours I would need 47gpm flow rate. it seems like a 0.75hp pump would do just fine for my application as long as my THD is under 65ft.

What do you think?

Here is a picture of my pool design:
http://gregtakacs.com/dpr/pool2.jpg