2.5" pipe upgrade from 2" Poly

[UncleMatt]

Hi all, first post and looking for some construction / equipment advice on a new residential pool:

PB recommending 2" Black Poly (std. in all their pool builds), but based on the limited information below and reviewing the various Pump/Pipe Sizing documents I believe upgrading to 2.5" Pipe will be worth the additional install costs. ($1500)

• 32000 gal free form pool (custom sized and 8000 gal larger than their largest offering)
• Hayward C4030 Cartridge filter & Hayward 900 OmniVS
• Hayward OmniLogic Automation
• 3 Hayward UCL LED 12v lights & transformer
• 2 Hayward SP1085 AutoSkim with 2" connections

Calculations determine:

• 32000 / 8 hours (turnover) / 60 = 67 GPM (minimum flow at turnover)
• Desired flow rate would be 78 GPM
• total pipe, including 45's, T's and 3-way Valves = 486 ft

Not looking to change equipment / brands, simply looking for pipe sizing confirmation or rationale to keep / upgrade.

 

[mas985]

Welcome to the forum!

Read This BEFORE You Post

We'd like to give you a few basic pointers of items that will help us, help you. From filling out a signature to posting test results.

www.troublefreepool.com

I have done this type of analysis many times and it is usually not work the trouble. However, the first mistake is believing in the turnover myth. Runtime is not dependent on targeting a certain number of turnovers per day.

Determine Pump Run Time

To figure out how many hours you need to run your pump, you need to know how fast your pump works. You can find this here.

www.troublefreepool.com

But to get to the details, you are missing some key components.

First, please separate fittings from pipe. Equivalent length changes with diameter.

What is the length of the straight pipe vs fittings that you are increasing in diameter?

What is the length of the straight pipe vs fittings that you are NOT increasing in diameter?

What valve types (i.e. check (spring or swing), 3-way, 2-way) are used in the plumbing?

Is there a single run pool to pad for the suction and return or are the some parallel runs (i.e. home run from the skimmer to pad and MD to pad)?

How many pool returns and what is the size of the eyeballs?

Do you have a heater and if so what kind?

Note too that increasing pipe size does decrease total head loss but it may not make that much of a difference depending on the other components of the plumbing system that do not change. Also, while reducing the plumbing head loss increases flow rate in the pump, it also increases energy use. People do not often think about this but if you maintain the same RPM in the pump, you will end up using more energy and not less. So to take advantage of reduced head loss, you must reduce RPM from what you had prior to reducing the head loss. So it isn't a slam dunk.

[EDIT] Just realized that this is a new pool and not a replumb. The cost of the larger pipe should not be $1500.

 

[UncleMatt]

Welcome to the forum!

Read This BEFORE You Post

We'd like to give you a few basic pointers of items that will help us, help you. From filling out a signature to posting test results.

www.troublefreepool.com

I have done this type of analysis many times and it is usually not work the trouble. However, the first mistake is believing in the turnover myth. Runtime is not dependent on targeting a certain number of turnovers per day.

Determine Pump Run Time

To figure out how many hours you need to run your pump, you need to know how fast your pump works. You can find this here.

www.troublefreepool.com

But to get to the details, you are missing some key components.

First, please separate fittings from pipe.

What is the length of the straight pipe vs fittings that you are increasing in diameter?

What is the length of the straight pipe vs fittings that you are NOT increasing in diameter?

What valve types (i.e. check (spring or swing), 3-way, 2-way) are used in the plumbing?

Is there a single run pool to pad for the suction and return or are the some parallel runs (i.e. home run from the skimmer to pad and MD to pad)?

How many pool returns and what is the size of the eyeballs?

Do you have a heater and if so what kind?

Note too that increasing pipe size does decrease total head loss but it may not make that much of a difference depending on the other components of the plumbing system that do not change. Also, while reducing the plumbing head loss increases flow rate in the pump, it also increases energy use. People do not often think about this but if you maintain the same RPM in the pump, you will end up using more energy and not less. So to take advantage of reduced head loss, you must reduce RPM from what you had prior to reducing the head loss. So it isn't a slam dunk.

Appreciate the reply, Everything will be 2.5" (breaking ground in August). Early enough to modify and change equipment.

Straight pipe = 316ft
Fittings = 170 ft
3 - Jandy 3 way (automated)
Home run from floor suction to pad
Home run from skimmers to pad
Pool returns - 4 - 1"
Heater = Hayward Summit XL140 Heatpump

Thank you

 

[mas985]

Straight pipe = 316ft

Does that mean that the distance from pump to pool ~100'?

Fittings = 170 ft

I would rather have the break down of 90s, 45s, etc.

Home run from skimmers to pad

How many skimmers?

The more parallel paths you have, the less pipe diameter matters.

3 - Jandy 3 way (automated)

Why three? Are you planning for a spa?

Sorry for so many questions but the configuration makes all the difference.

 

[UncleMatt]

Does that mean that the distance from pump to pool ~100'?


I would rather have the break down of 90s, 45s, etc.


How many skimmers?

The more parallel paths you have, the less pipe diameter matters.


Why three? Are you planning for a spa?

Sorry for so many questions but the configuration makes all the difference.

Mark,

Appreciate the ?'s, will help get this correct and efficient. pool is custom design freeform 28x46

Pool to Pad is 35' and from the revised quote - 5-90s, 3-Ts, 10-45s, 280 ft pipe (original quote was 400 ft, 2.0" flex pipe) - std package quote

2 skimmers - opposite sides of pool

3 valves (one for future spa addition (non-operational when pool is opened)

 

[mas985]

Spas generally require at least 2 3-way valves because you have to swap both the suction and return sides. Sometimes a third valve is used for the bypass.

Anyway, assuming a1500 RPM speed, here are the operating points for each plumbing system:

2" - 1500 RPM, 37 GPM, 11.2' of head & 141 watts
2.5" - 1500 RPM, 39 GPM,10.7' of head & 144 watts

As you can see, the larger plumbing uses more energy at the same RPM but it also delivers higher flow rate. If you force the 2.5" plumbing to the same flow rate as the 2" plumbing (1430 RPM), you get this operating point for 2.5":

2.5" - 1430 RPM, 37 GPM, 9.75' of head & 126 watts

So when you compare the two based upon flow rate, you would save 15 watts of energy which is not all that much. Even if you run the pump 24 hrs per day, that is only 360 watts per day and at $0.10/kwh, that is $0.036/day. To pay off $1500, it would take ~42,000 days of operation. Assuming, the pool is open for only 100 days a year, that is 420 years.

So don't upsize the pipe if you are just trying to save money. On the other hand, I would never use black poly in a pool either. It is too prone to leaking. So avoiding that is worth the extra cost. You might ask the PB what the cost would be for 2" ridged PVC.

 

[UncleMatt]

Great info. Thank you. I was looking at flow rate and turnover, appreciate the education. Still a little cloudy at 37 GPM we would only be filtering 17k every 8 hours. Why then all the topics on 6 fps flow rate, pool turnover 4 times, etc.

Not about saving money (at this investment we want it correct) the upfront or to payoff the energy costs as we understand the annual costs for pool maintenance. Was looking to ensure we have the most efficient system and if moving up to 2.5" will ensure that efficiency, then it would be worth the cost. I hear too many complaints from neighbors with new pools mostly with 1.5" flex pipe (watched the installs) and assume they had not spent the time researching the topic, but took the PB professional opinion as fact. Likely more issues than pipe sizing.......

I have likely read too many stories about taking the time to properly design the system vs the out of box service (this is what we do, it will work fine) thus the questions.

Appreciate the help and clarity. I'll work with the PB..

 

[mas985]

Why then all the topics on 6 fps flow rate, pool turnover 4 times, etc.

The 6 fps is a recommended maximum velocity based upon entrapment requirement of the VGBA legislation. Lower velocity is better for efficiency.

The turnover recommendations are based upon a false information that tends to get passed on from site to site. Read the pump runtime study in my signature. The summary of the that study shows that turnover is not a very good metric for determining how to maintain pools.

Efficiency is not really that much different between 2" and 2.5" so that is not really at play here. But efficiency is really only about energy use so I am not sure why you would consider it outside of that context.