Purchasing a new AG Pool. Need advice...

[BigDave]

??
radius squared x pi x depth x gal/cft
15.5*15.5*3.14*4*7.48=22,571

I'm so sorry to contradict, but I must respectfully point out that half of 33 is 16.5 and that (33/2)^2*Pi*4*7.48=25590.534.
15.5 is the gallons in a half-barrel. Is it the weekend yet?

[Serapium]

Thanks for the input! I know that a 1HP pump is capable of circulating enough water to filter the volume of the pool... I guess what I'm actually wondering is if the filtered H2O coming out the return to the pool comes out with enough force to circulate water evenly throughout the entire pool. In other words, with a 1HP pump turning over 30K gallons a day, are you really filtering 30K gallons, or are you filtering 10K gallons three times?

[PoolDoc]

@ Janet, Dave: my bad! sorry! (thanks for the correction!)

@ Serapium: what actually happens when you circulate water is mind-numbingly complex, but roughly you can think of it like this:

UP: unfiltered water in pool
CP: clean filtered water in pool
UF: unfiltered water in pipes
CF: clean filtered water in pipes

1. Initially, the system pulls UP into the pipes, pushes UF through the filter and discharges CF into the pool.

2. But, now the pool contains UP + a small amount of CP. There's a lag in mixing -- how much lag depends on the way the pool returns and drains are arranged. But anyhow for the next few minutes, the system continues to pull ONLY UP from the pool, and return only CF to the pool.

3. But, then, the system begins to pull a mix of UP and CP into the system, so the filter NOW is filtering water that is mostly UP, but contains a little CP. CP has ALREADY been filtered, so that's pretty much wasted effort.

4. As time goes on, the system pulls an ever decreasing amount of UP into the pipes and more and more CP, wasting more and more of the filtration by filtering a mix of UF and CF.

So, even though a 100GPM system can filter a volume of water EQUIVALENT to the volume in the pool, in only 1.7 hours, it will take MUCH longer than -- probably at least 10 cycles before 99% of the water in the pool has been filtered 1 time.

For a typical pool with side inlets, a main drain, and skimmers and an 8 hour turnover rate, it will take around 3 days to filter 99% of the water. Commercial pools, with laminar flow floor inlets and primary circulation through skim gutters can accomplish the same task in just one day. And, I've actually worked with one pool with this design: it was MUCH faster to clean up, then pools with more typical piping systems.

[Serapium]

Thanks, Ben! So, I've then come full circle back to one of my original questions at the beginning of this post

"... is a single 1 HP pump really enough for a 33' pool? Would I be better off with the addition of another 1 HP pump/ skimmer to aid in circulation on the other side of the pool?"

Your thoughts? It seems that the addition of another pump on the opposite side of the pool to aid in water circulation would make the beginning of the efficiency progression you laid out even LESS efficient, as you would likely have a higher proportion of C.P. to U.P. at the beginning of the cycle. However, if the pumps were only going to run for.... say... eight hours a day, would the addition of the second pump not increase the overall efficiency of the system when looked at from a macro scale? What if you were to run both pumps for two hours at a shot on a timer spaced out through five segments of the day? Seems to me that over time you would filter more U.P. in less than half the time (hence using less energy) than if you didn't have the second pump. It's been years since I've tried to do the calculus involved in that kind of computation so I'm a little rusty, but I think I'm running under correct assumptions. In my old 15' pool this wasn't really an issue since the C.P. returned to the pool caused distinct circulation within the overall vessel, but I don't think that is going to be likely given the fluid mechanics involved with the change from a 5,300 gallon vessel to a nearly 28,000 gallon vessel.

[PoolDoc]

Running far behind on forum questions now, so I'm gonna be brief:

Yes, a 1HP pump, especially in the combination I laid out for you, will perform very well. If you want to OPTIMIZE performance, putting 2 - 3 inlets on sides of the pool OPPOSITE the skimmer, using larger orifices on the eyeballs, and putting 1 of the inlets LOW and close to the floor, will help accomplish that goal.

[Serapium]

Ah, I see! Thanks!