Pump Sizing Question

[liz+3]

Just getting ready to break ground on a new IG gunite pool. Here are some specifics:

Pool size: 24 X 33 (approximate area = 485 sq. ft., approximately 16000 gals.)
Pool depth: 3.5 x 5 x 3.5
Filter: 60 sq. ft. Pentair DE
Pump: Pentair Whisperflo - 2 HP (high performance) - 2"
Valves: Compool -never lube 2" - 2.5"
Skimmers: 2 Bermuda Pentair 2" lines (separate line, separate valve)
Inlet: 5 pool return inlets
SWG: Pentair Intellichlor 40
Heater: Pentair Minimax

I am concerned about high energy costs for running the pump. I am seriously considering a two speed pump or possibly the new Pentair Intelliflo 4 x 160 multi-speed pump.

While reading through many posts on this forum, I have noticed other pool owners are operating smaller HP pumps for pools larger than mine.

How can I be sure that I do not end up with an oversized pump even if it is two/multi speed?

Thanks for the help. This is a great forum.

Liz.
Houston, Texas

[mas985]

Why such a large pump? You did not mention water features or a spa so your pump may be way oversized. You could easily get by with a 3/4 HP and for more energy savings go with a 3/4 HP 2 speed. Also, with your plumbing, my guess is your head loss will be fairly low so you will have plenty of flow with a 3/4 pump.


Good luck on your pool.

[liz+3]

Mark,

Thanks for the reply.

Yes, there is a spa, here are the details:
12" raised
7' round shape
6 spa jets with 1 HP Polaris QT blower

There are no water features. Just a 3' wide spillway from the spa to the pool (I don't think this qualifies as a water feature?)

I will check to see if the Intelliflo pumps are available in lower horsepower or smaller size.

Can you suggest an accurate/simple way to size the pump properly?

Thanks,

Liz
Houston, Tx.

[mas985]

For most spas, you will need about 15 GPM/jet for a medium strength jet. So for 6 jets, this is 90 GPM. If you have one pump for everything, I would go with a 2 HP 2 speed pump. If you have a separate jet pump, then you could get away with a 1.5 HP pump for the jets and a 3/4 HP for filtration.

I prefer the two pump configuration as it will allow you some flexibility with the spa and pool. I have this and once the spa heats up, sometimes I put the filter back on the pool, I have solar, and use the jets in the spa. You can only do this with a two pump configuration.

As to your last question, to determine the pump size properly, a full head loss calculation is required for the pool and spa. Once the head loss is known, you should be able to determine the pool turnover rate and the spa jet strength. Unfortunately, many pool builders do not know how to do this so they will usually go with a high HP pump to make sure they have enough flow.

Given the size of your pool, you only need 33 GPM for an 8 hour turnover. This is not very much and a 3/4 HP pump will provide more than that even on low speed. However, you need the HP for the spa jets depending on how strong you want them. The Intelliflow will give you some flexibility in case you sometimes want weak jets. Some people will complain jets are too weak will others, too strong so it is somewhat of a personal preference.

There really is no one answer only a lot of options. One thing I would strongly suggest is to have a low speed on the filtration pump. This will save you a lot of money in the long run.

Hope this helps.

[liz+3]

Mark,

Thanks for the help.

I would certainly want strong spa jets so maybe the 2 HP pump is what will be needed.

As of now I am planning to go with the Intelliflo 4x160 and use the lower speeds for filtration.

Liz
Houston, TX