Review of proposed plumbing change

[ryguy]

My old single speed pump died and I'm planning to replace it. I think I've settled on the Pentair 1.5 HP Superflow the VS (had a 1.5 hp Superpump before). I decided to rip out all of the 1.5" plumbing on my pool pad even though I'm not changing any other equipment at this time. My plan is to replace it with all 2" piping to get more efficient suction from the main drain and skimmer and more water cycling back through the returns.

I've attached a diagram of what I'm proposing but since I haven't started replacing the plumbing yet I can still modify the design if needed. I would like to get input from those who know a lot more about pool plumbing than me. I apologize that the diagram is rather small and archaic but hopefully it's readable.

For reference, the pool is 15'x37' and approx 24-26k gallons. It has one skimmer, 1 main drain, 1 return line that tees to 2 returns in the pool. Also has another return line that was being used to power a Polaris cleaner. However, I've removed the cleaner and have no plans to use it so the diagram shows that line being converted over to another return line. Please let me know your thoughts/suggestions on the proposed design and if you think the upgrade to 2" pad plumbing will help or create any issues for me. Thanks!

 

[mas985]

My plan is to replace it with all 2" piping to get more efficient suction from the main drain and skimmer and more water cycling back through the returns.

Just changing the plumbing on the pad isn't going to do much. The effect will be quite small. If it were me, I probably wouldn't bother unless there was a specific issue with the plumbing besides pipe size.

What exactly is driving this decision?

Also, if you want to know approximately the magnitude of change, please give dimensions for each of the pipe runs.

 

[ryguy]

Mostly I want better skimming and pull from main drain too. The pool was plumbed using several street elbows and more 90s than were really needed and I've felt that restricted the flow. Additionally I thought with the new VS pump that my flow might be better (more efficient) at low rpms by running thru the 2" on the pad.

The main drain line is about 45' and the skimmer about 35'. The one return that has a tee is approx 60' at the furthest return and 40' at the closest. The old cleaning port (to be a new additional return now) is about 50'. All is 1.5" pvc.

 

[mas985]

Using the numbers you gave me, here are the estimated flow rates with the VS pump:

All 1.5" Plumbing: 70.1 GPM, 61.7' of head, 1962 Watts, 3450 RPM
Pad 2" Plumbing: 72.6 GPM, 60' of head, 1984 Watts, 3450 RPM

The difference is less pronounced with lower speeds

All 1.5" Plumbing: 24.4 GPM, 7.5' of head, 146 Watts, 1200 RPM
Pad 2" Plumbing: 25.2 GPM, 7.3' of head, 147 Watts, 1200 RPM

A 4% change in flow rate is not worth the effort in my mind. I don't think you would ever notice that.

 

[ryguy]

Wow thank you for providing those calculations! Not sure how you were able to figure all of that out but it is telling and like you said not as much gain as I had anticipated.