pool plumbing for new construction

Heliman500

Active member
Nov 19, 2020
32
Rescue, CA
Hello folks, We are in the process of starting a new pool build and just broke ground excavating yesterday.

After talking to a few different plumbers regarding the plumbing for the pool, it appears there might be a few different ways to skin a cat, however, I am looking at plumbing in a fashion that furnishes maximum efficiency.

Here are some basic details of pool:
Rectangular shape, Size 14x36 with a 5x10 offset cabo shelf. Shallow end depth 3’6”, deep end 5’. Volume 16,000 gallons. Pool will be situated away from trees or tall vegetation. I’ve owned a pool before which ran pentair equipment without any problems so I am leaning towards pentair equipment again. I am also a fan of sand filters. The pool will not be heated. The equipment pad will be located 10 feet from the corner of the deep end.

I am wondering if anyone could make recommendations on the amount of skimmers, return eyes, pipe diameter, and pump size needed.

Thank you very much for any advice. @mas985
 

cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
5,930
Southern OK
Welcome to TFP :) This one is easy

at least 2 skimmers, 1 on each side where the wind is moving.. mine is north and south..
3 to 4 returns
Pipe at least 2 inch

pump 3hp VSF intelliflo
01105655230163.231.323.9550Hz/60HzUL/NSF/APSP2" x 2"

As for the sand filter, they blow through 100 to 300 gallons of water for every backwash, a cartridge filter will help with your water shortages and you can go a year without cleaning it, much better filtering and just all around better :)

I have the 320 and I think it would fit perfect for your 16000 gallons, my PSI goes up 1 for the year.. you could go to the 420 if you are open all year around...
 

Heliman500

Active member
Nov 19, 2020
32
Rescue, CA
Welcome to TFP :) This one is easy

at least 2 skimmers, 1 on each side where the wind is moving.. mine is north and south..
3 to 4 returns
Pipe at least 2 inch

pump 3hp VSF intelliflo
01105655230163.231.323.9550Hz/60HzUL/NSF/APSP2" x 2"

As for the sand filter, they blow through 100 to 300 gallons of water for every backwash, a cartridge filter will help with your water shortages and you can go a year without cleaning it, much better filtering and just all around better :)

I have the 320 and I think it would fit perfect for your 16000 gallons, my PSI goes up 1 for the year.. you could go to the 420 if you are open all year around...
@cowboycasey thank you very much for the detailed response. I had a suspicion I may be steered away from the sand filter, and that’s totally ok, I think you may have persuaded me back to a cartridge filter. I don’t expect to have much of an issue with leaves or surface debris but do expect a large amount of dust (rural environment) which was why I was thinking of going with a sand filter initially. Any thoughts if I’d see a return on investment if I stepped up to 2.5” suction diameter? Thank again!
 

cowboycasey

Gold Supporter
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TFP Guide
Jul 3, 2013
5,930
Southern OK
2.5 or 3 inch for suction side is a great thing, I think I may just do 2 inch but I am planning on 3 skimmers and 1 suction side vacuum port just in case... still debating going 3 inch though, what's another 50 bucks :)
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,037
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
I would highly recommend a cartridge filter, especially for California. Many cities here now require water recapturing for backwashed filters which kind of negates some of the benefit of backwashing. A large cartridge filter will need to be cleaned maybe once per year so it doesn't require much effort for maintenance.

One thing to be aware of for the number of skimmers is that as you increase the number of skimmers, the RPM of the VS pump will need to be increased proportionally and energy use will also increase. The reason for this is that if the flow rate is too low, the water will go around the sides of the weir door instead of over the weir door and if that happens, no skimming is actually performed and debris will pile up at the skimmer mouth.

So 2 skimmers will require 2x flow rate/RPM as a single skimmer and 3 skimmers will require 3x the flow rate/RPM as a single skimmer. In a pump, as the RPM increases, so does the energy and by larger factor. A 14'x36' pool should be able to get away with a single skimmer. Two skimmers are sometimes desired if the wind can come from more than 1 direction depending on the weather. However, very few pools should require 3 skimmers and from an energy perspective would be more expensive to run.

I have two skimmers in my 16'x36' pool but most of the debris ends up in only one of the two skimmers because of wind direction. Plus, to get the lowest RPM possible, I have shut down one of the skimmers to a very slow draw just to keep the lines chlorinated.

As for pipe size, I think 3" is overkill. If you plan on running a VS pump on the lowest RPM possible, the difference in head loss and energy use is insignificant. For example, assuming 15' runs, a cartridge filter, dual suction lines pool to pad, single return line pool to pad and typical pool plumbing layout, a plumbing system with 2" return pipe and 2.5" suction pipes, would have an operating point at 1000 RPM of 45 GPM @ 5.11' of head and 133 watts. Increasing the pipe size to 2.5" return and 3" suction, would change the operating point to 47 GPM @ 4.75' of head and 134 watts. You will notice that energy use goes up with larger pipe but so does flow rate. So the GPM/watt is better with the larger pipe but not by much. However, a byproduct of large pipe is that sometimes it can be too large. The 2.5'/3" scenario might have pump cavitation problems near full speed because the head loss in the plumbing is actually too low for the pump, depending on the pump.
 
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Heliman500

Active member
Nov 19, 2020
32
Rescue, CA
Hey folks, my pool project is underway. Rough plumbing is done. Getting to the point where I need to start looking at equipment to purchase. I am having a hard time understanding the difference (in layman’s terms) the difference between the Pentair VS and VSF pumps. The pool will be 16,000 gallons. 1 skimmer, 4 Returns, one pentair bubbler on the shelf with separate control valve, filter will likely be pentair 420. Any recommendations on type and HP of pump needed. Thank you in advance!
@mas985 @cowboycasey
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,037
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
VS = Variable Speed
VSF = Variable Speed & Flow

With a VS, you can only set RPM, with a VSF you can set either RPM or GPM. Either one will work just fine and I don't think there is much difference in price. The Intelliflo VSF would be a good choice.
 
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Heliman500

Active member
Nov 19, 2020
32
Rescue, CA
VS = Variable Speed
VSF = Variable Speed & Flow

With a VS, you can only set RPM, with a VSF you can set either RPM or GPM. Either one will work just fine and I don't think there is much difference in price. The Intelliflo VSF would be a good choice.
Thank you. That makes sense. What are your thoughts on pump HP? It appears the general consensus is bigger the better. I don’t think my well pump is more than 1 hp and sends water up vertically 600’ and does just fine.
 

cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
5,930
Southern OK
the bigger the motor is the less power it uses to move water at a lower speed.. take a 1.65 hp and a 3 hp, if both are run at 1800 rpm the 1.65 will cost more to run as the motor is working harder to get that rpm..
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,037
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
the bigger the motor is the less power it uses to move water at a lower speed.. take a 1.65 hp and a 3 hp, if both are run at 1800 rpm the 1.65 will cost more to run as the motor is working harder to get that rpm..
The smaller hp pump will use less energy at the same rpm as a larger hp pump because it would be delivering lower flow rates.

However, if the two pumps are at the same flow rates, the larger hp pump may have lower energy use but not always. It depends on which two pumps are compared. The difference is usually small and not worth comparing.

The main benefit of a larger hp pump is that it will be much quieter at the same flow rate because the rpm will be less. Another advantage is that the impeller vanes are wider so less likely to get clogged by debris.
 
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cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
5,930
Southern OK
Thank you for clearing that up :) Every time I think I know how these motors work and then I find out I am almost correct but not...