Plumbing Run Distance Concerns?!? Is 100 feet too much?

[troublefreefun]

I'm in the midst of design and the least obtrusive pool equipment location is 100 feet away from the spa, 90 from vac line and 80 feet from the drain. The alternative is that I have the equipment behind the end of the pool and knock about 60 feet off of each of those numbers. I could put the in-floor cleaning rotating box substantially closer (50' feet closer) if that helps so that all of those small runs into the in-floor heads are only 30 to 40 feet if that helps anything.

Are there concerns with these 100/90/80 feet long distances? It would come with the same number of 45's and elbows as short run distance I imagine.

What am I giving up (if anything beyond additional plumbing costs) by having longer runs?

Exact equipment isn't specified yet but it will be variable speed and a 2hp blower.

Comments or suggestions?

 

[JamesW]

The distance does not matter as long as the lines are sized correctly.

What is the flow required for each line?

 

[JamesW]

Equipment Pad Best Practices - Further Reading

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[JamesW]

How many jets for the spa?

What is the flow required per jet?

Do you want a separate jet pump?

Will the equipment be at the same elevation as the pool and spa or higher or lower?

If higher or lower, how much?

 

[troublefreefun]

The distance does not matter as long as the lines are sized correctly.

What is the flow required for each line?

I am not positive. I'm in a bit of a preliminary design and I don't want to get too far down in design and then later decide to move locations of the pool equipment. I would prefer it further away due to backyard design but not at the cost of a pool that doesn't work well. I realize this doesn't answer the direct question. Doesn't design take place and then it gets engineered?

Spa will have 7 jets.
Flow will be ideally 19 GPM and no less than 16 GPM.
I'm alright to have a separate jet pump if it is needed.
Equipment will be at the same elevation as the top of the pool/spa for the long distance potential location. For the shortest distance location it will be approximately 18" lower than the top of the pool/spa. The longer answer about elevation is that the pool sits a bit higher than the rest of the yard.

I should also note that the long distance pad location would mean going under a sports court (that isn't there yet, but will after all landscaping/pool is complete). Is this a major NO NO to put pool plumbing under something you cannot remove?

 

[proavia]

Post a few pics of the area, along with a drawing or two to help us better visualize what you are working with.

You may find it better to have the pool equipment closer to the pool and/or not have piping running under an expanse of concrete. The equipment can be hidden with hardscape and landscape elements.

Also, consider having soft water supplying your pool autofill.

 

[JamesW]

Spa will have 7 jets.
Flow will be ideally 19 GPM and no less than 16 GPM.

That is 133 GPM.

So, the suction needs to be at least 3".

Each 90 adds the equivalent of 7.7 feet of pipe , so a 100 foot run with 5 90s is equivalent to 138.5 feet of pipe.

As long as the suction velocity is below 6 ft/sec and the head loss is below 8 feet, the plumbing is sized correctly and the distance does not matter.

Pipe Size and Flow Rates.​

You want to keep the water velocity below 6 ft/sec on the suction and below 8 ft/sec on the pressure side of the pump.[7]

Pipe Size	6 ft/sec	8 ft/sec
1.5"	38 GPM	51 GPM
2"	63 GPM	84 GPM
2.5	90 GPM	119 GPM
3.0"	138 GPM	184 GPM
4.0"	235 GPM	312 GPM

Hazen-Williams Water Flow Formula: Head Loss, Data, Charts & Calculator

Friction head loss (<i>ft_H2O per 100 ft pipe</i>) in water pipes can be estimated with the empirical Hazen-Williams equation.

www.engineeringtoolbox.com

You could put the equipment 700 feet away if you used 4" PVC for the suction.

 

[JamesW]

Doesn't design take place and then it gets engineered?

Correct.

Design it how you want and then figure out the plumbing.

The main point is that (within reason) the equipment can be as far away as you want as long as the pipe is sized correctly.

 

[troublefreefun]

@JamesW Thank you very much for the time spent running the calculations and explaining. You mention suction under 6 and pressure under 8. Is less better? Your example reflects suction as 6.04 (close enough) and pressure as 4.57 (way under 8). Changing from 3" to 3.5" pipe would result in suction at 4.4 and pressure at 2.16. I realize that pipe diameter has an exponential cost difference as you get larger but is it better to play it safe or am I overthinking this?

By the way, I input in 200 instead of 100 ft in the Hazen Williams Water Calculator and the suction stayed at 6.04 and the pressure went to 9.14. So we are above 8 on the pressure. In a super high level can you explain to me what happens in a scenario like this where the suction is in the range it needs to be but the pressure is not?

 

[JamesW]

Velocity is the speed of the water moving through the pipe.

The higher the velocity, the more friction/drag there is between the water and the walls of the pipe.

The friction increases exponentially by a square factor.

So, if you double the flow/velocity, the head loss is 4 times higher.

The head loss grows linearly vs. the length, so twice the length, means twice the head loss.

Changing the length does not change the velocity.

If you double the length, the water goes the same speed; it just takes longer to make the trip.

Affinity laws - Wikipedia

en.wikipedia.org

 

[JamesW]

By the way, I input in 200 instead of 100 ft in the Hazen Williams Water Calculator and the suction stayed at 6.04 and the pressure went to 9.14. So we are above 8 on the pressure.

Technically, the suction head loss can be up to about 17 feet before the pump will cavitate or underperform.

8 feet is chosen as a conservative design rule.

Many local codes require velocity below 6 ft/sec for suction and below 8 ft/sec for pressure/return.

Following these guides, the head loss will be acceptable for plumbing up to 100 feet long.

Equipment at elevated positions will create static head loss.

So, a system at 5 feet above the pool will start with a 5 foot static head loss, which means you only have 3 feet of dynamic head loss available for design or up to 12 feet technical limit.

 

[JamesW]

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[JamesW]

Your system should be designed to have a System Curve of Curve "C" or better.

To choose the correct pump, use the pump performance curve and the system curve.

The NPSHr is = 34 - Head loss.

NPSHr is the Net Positive Suction Head Required, which is the absolute pressure at the entrance to the impeller.

The NPSHr of this pump is about 12.5 feet at 142 GPM.

So, the head loss can be up to 34 - 12.5 = 21.5 feet before the pump would underperform or cavitate (at sea level).

In any case, try to keep the suction head loss below 8 feet for design purposes.

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[JamesW]

System Head Loss = C_TF^2.

C_T = C_S + C_P.

Coefficient for the Total System = Coefficient for the Suction plus Coefficient for the Pressure.

C = Head Loss/Flow^2.

C_S = 6.59/135^2 = 0.00036159 for a suction line at 150 feet long and 3" diameter.

H_S=0.00036159F^2 (Suction Only).

 

[1poolman1]

I am not positive. I'm in a bit of a preliminary design and I don't want to get too far down in design and then later decide to move locations of the pool equipment. I would prefer it further away due to backyard design but not at the cost of a pool that doesn't work well. I realize this doesn't answer the direct question. Doesn't design take place and then it gets engineered?

Spa will have 7 jets.
Flow will be ideally 19 GPM and no less than 16 GPM.
I'm alright to have a separate jet pump if it is needed.
Equipment will be at the same elevation as the top of the pool/spa for the long distance potential location. For the shortest distance location it will be approximately 18" lower than the top of the pool/spa. The longer answer about elevation is that the pool sits a bit higher than the rest of the yard.

I should also note that the long distance pad location would mean going under a sports court (that isn't there yet, but will after all landscaping/pool is complete). Is this a major NO NO to put pool plumbing under something you cannot remove?

Pool plumbing is, virtually, always under something you can't easily remove, but there is "always a bigger hammer."
Do yourself a favor and use the very least amount of 45s, none is better, underground. Ask any leak detection/repair company that does the repairs and they will tell you that most under -ground, -paver, -deck, leaks are at those fittings.

 

[troublefreefun]

What about the in floor cleaning system t-valve? Rather than run each of the heads 100+ feet to the pool equipment location is it advisable mathematically to have that system much closer to the pool and then have the length in the run to the pump that is far away? Or is this dependent upon the specifications of the t-valve product?

 

[JamesW]

You can calculate it both ways.

1) Head near equipment with short supply and 5 long returns.
2) Head near pool with a long supply and 5 shorter runs.

Either way, use the 8 feet per second rule for each line.

What is the flow required for the In-Floor Cleaning System?

I would eliminate the In-Floor Cleaning as it is a huge energy waste and a robot will do a better job for less power.