PB says Intelliflo VSF is maxed out at 75 gpm. Need some guidance

[brandon#]

Hi everyone,


We are in the middle of installing a fiberglass pool and have most of the plumbing connected, but have not poured the concrete deck yet. I'm playing around with the pump speeds and noticed that I can't flow much more than 75 gpm. This is our first pool, so I'm still learning how these systems work. However, I started researching and noticed the skimmer we have is rated at 75 gpm, and 2" pipe maxes at around 75 gpm as well.

My PB is convinced the 011056 VSF is maxed out at 75 gpm. He said no matter how many skimmers or the size/number of suction pipes that I have, the flow is restricted due to the 2" inlet port and therefore the flow is ultimately limited by that size. Needless to say, he is not one to calculate head or reference pump curves. (insert face palm emoji here)

I attached a picture of the exact pool, tanning ledge and water feature setup we are copying for reference. I knew it would take a lot of water to support these features so I was trying to get equipment that could keep up.

I'm fairly certain the only way we could achieve anywhere close to 120 gpm (the filter flow rating) is with a second skimmer and parallel 2" suction lines that merge to 2.5" near the pump.

Here is what we have:
Intelliflo VSF 011056
Pentair Clean and Clear 320
Pentair Ultratemp 140
IC40
Intellicenter

Any advice would be greatly appreciated. This build is definitely pushing the PB out of his comfort zone of plain vanilla pools and 30 year old equipment.

 

[Dirk]

Probably will need @JamesW to weigh in on this one, but I think you're mistaking max flow rates for optimal. While a filter might be rated to withstand 120gpm, you certainly don't need to drive it at that rate. The most flow I need, to drive my solar, is about 40gpm, and the pump is going at a pretty good clip to achieve that. My normal filtration requires way, way less than that.

Does the pump drive the water features adequately, or not?

I would think that a Pentair VS pump could drive those features, but James would know. If not, and you need a second pump, then I think you'll also need a dedicated suction port for the second pump, which will have to go in before the deck does. James?

 

[Flying Tivo]

Forget about Flow and use rpms. For filtration almost everyone uses around 1100-1200 depending on skimming needs to keep clean. Also for the SWG i use around 1200 when producing Cl or whatever flow needs to to keep the flow led on the IC green.

 

[brandon#]

I omitted the main reason we need that much flow. My concern wasn’t meeting the filter’s flow capacity. It’s meeting the minimum flow for a large water slide that requires 120-150gpm which will be a future addition.

I just began noticing that it couldn’t break 80 gpm and started second guessing the plumbing setup.

 

[ajw22]

Your Ultratemp is a major restriction in your plumbing. Do you have a heater bypass that you can bypass the UltraTemp when you want more flow?

Heater Bypass - Further Reading

www.troublefreepool.com

I think to get the flow rates you want you need to have the right dedicated pump that does not go through a filter or heater.

@mas985 can fill in the details.

 

[brandon#]

Your Ultratemp is a major restriction in your plumbing. Do you have a heater bypass that you can bypass the UltraTemp when you want more flow?

Heater Bypass - Further Reading

www.troublefreepool.com

I think to get the flow rates you want you need to have the right dedicated pump that does not go through a filter or heater.

@mas985 can fill in the details.

Yes,
I have a heater bypass.

If the skimmer is rated to a max of 75 gpm, can all other variables be null and void? Isn’t that the flow-limiting bottleneck at the very beginning of the system?

 

[ajw22]

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.

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

 

[Dirk]

Ah, the slide. Yes, that's not a minor detail! Not quite sure how you got here. All the GPM requirements and restrictions are easily determined ahead of time, which then require some "engineering" to configure correctly, including pipe size, pump size, etc. Which it now seems you are stuck doing. Don't get me wrong, your "investigation" before the deck goes down is spot on, and is going to save you from what otherwise might have been a major disappointment. And it's fine that you're turning to TFP for some guidance. But what you need is a pool plumbing professional to calculate this out for you, on the PB's dime, and then have the plumbing reconfigured as needed. So that should be your ultimate recourse.

That said, it's certainly logical to assume a 120-150gpm requirement is not going to be serviced by that skimmer. So you need a second suction port, which could be another skimmer or, as I mentioned, a dedicated port that runs to a second pump. One that would then drive the slide, and possibly some or all of your other water features. I would guess the bubblers could stay on the filter pump circuit. The pond waterfalls should too, so that water gets filtered. So then the two fountains and the slide go on the other pump. That pump would get fed by dual suction ports (with anti-entrapment covers) that could be located somewhere in the side of the pool. Something like that. Just a matter of the right guy doing the math for you, and the existing plumbing modified to accommodate the calc's...

 

[JamesW]

As you can see from the graph, the maximum flow is about 170 gpm at full speed and low resistance.
For best performance, the maximum flow should not exceed about 140 gpm.
The flow depends on the pump speed and the total head in feet of water.
To get total head in feet of water multiply the filter pressure by 2.31 to get the return head. You would also need to get the suction head from a pressure gauge. To estimate total head from return head, multiply return head by 1.333.
For example, if the return pressure is 23 psi, the total head would be estimated at about 1.333 x 23 x 2.31 = 70.8 feet.
Looking at the graph for 3,450 rpm at 71 feet of head gives about 119 gpm.

Suction should not exceed 6 ft/sec and return should not exceed 8 ft/sec.
Size.......6 ft/sec......8 ft/sec.
1.5"...........38...............51 gpm
2"..............63...............84 gpm
2.5............90.............119 gpm
3.0".........138.............184 gpm
If you have a single 2” suction line, the flow should not exceed 63 gpm.
You can calculate the head loss of the suction line.
For example, if you have a single 2” PVC pipe (actual I.D = 2.067”) that is 100 feet long and 119 gpm, the head loss would be 22.8 feet at a velocity of 11.4 feet per second.

Hazen-Williams Friction Loss Equation - calculating Head Loss in Water Pipes

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

 

[Dirk]

Thanks James!

Uh, what he said. Which just reinforces my earlier post (#8). You need someone onsite, who's qualified, to do all the measuring and calculating... You could figure it out yourself, with help from our experts, but you don't want to do that. The plumbing spec needs to be done by, and warranted by, the PB, so that when it's all done, and doesn't work, he'd have to fix it. If you use spec's from here, or those that you calc yourself, then any failures would be on you...

But gather enough ammo from here to present it to the PB, to make the point that he needs to revisit the plumbing and redo it...

And then, like you just did, double-check that work, before the deck goes down, to make sure it's adequate.

Good catch, by the way. Most folks wouldn't have bothered, and only discovered this after the pool was done.

 

[brandon#]

Ah, the slide. Yes, that's not a minor detail! Not quite sure how you got here. All the GPM requirements and restrictions are easily determined ahead of time, which then require some "engineering" to configure correctly, including pipe size, pump size, etc. Which it now seems you are stuck doing. Don't get me wrong, your "investigation" before the deck goes down is spot on, and is going to save you from what otherwise might have been a major disappointment. And it's fine that you're turning to TFP for some guidance. But what you need is a pool plumbing professional to calculate this out for you, on the PB's dime, and then have the plumbing reconfigured as needed. So that should be your ultimate recourse.

That said, it's certainly logical to assume a 120-150gpm requirement is not going to be serviced by that skimmer. So you need a second suction port, which could be another skimmer or, as I mentioned, a dedicated port that runs to a second pump. One that would then drive the slide, and possibly some or all of your other water features. I would guess the bubblers could stay on the filter pump circuit. The pond waterfalls should too, so that water gets filtered. So then the two fountains and the slide go on the other pump. That pump would get fed by dual suction ports (with anti-entrapment covers) that could be located somewhere in the side of the pool. Something like that. Just a matter of the right guy doing the math for you, and the existing plumbing modified to accommodate the calc's...

Thanks for all of the info! Hopefully this fiasco is providing some entertainment to some of the pool experts here.
I really appreciate the advice.

I wasn’t aware that a “port” in the side of the pool was an alternative to using a skimmer on the suction side. That’s good to know.
Installing a second pump that’s separate from the filter and heater sounds like the way to go to ensure we never run out of flow for the ginormous slide I failed mention in the original post.

 

[JamesW]

For a high flow water slide, you want the Intelliflo XF, which will take a 3” coupling to the outside of the union.

As you can see from the curve, the pump can get to about 220 gpm with about 180 gpm being a practical maximum.

If you are OK at 138 gpm, the suction can be 3”. If you want more than 138 gpm, you have to go to 4” pipe or maybe (2) 2.5” pipes from 2 separate “unblockable” main drains or from two individual sets of two main drains tied together.

The suction intakes have to be rated for the maximum possible flow and the intake can be a single "unblockable" drain or two separate drains. For 150 gpm, I would do 2 unblockable drains with 2 separate 2.5 inch PVC lines to the pump or 2 sets of drains with each on their own 2.5" PVC pipe to the pump.

Alternatively, you could tie the two unblockable drains to a single 3" line (limit 138 gpm) to the pump or 4 regular drains to a 3" line to the pump for up to 138 gpm or a 4" line at over 138 gpm.

The slide pump should be separate from the main filtration pump.

The slide pump should be on its own dedicated suction and return.

The return needs to be at a 3” line to provide up to 184 gpm without exceeding 8 feet per second.

https://www.pentair.com/content/dam/extranet/product-related/product-manuals/pool-and-spa-equipment/intellifloxf/IntelliFloXF_Variable_Speed_Pump_Installation_and_Users_Guide_English.pdf

https://www.pentair.com/content/dam/extranet/pentair-pool/residential/brochures/pool-pumps/IntelliFloXF_Variable_Speed_Pump_English.pdf

IntelliFloXF® Variable Speed Pool and Spa Pump

The Pentair IntelliFloXF Variable Speed Pool & Spa Inground Pool Pump is an ENERGY Star certified pool pump offering savings for large pools. Learn more.

www.pentair.com

 

[Dirk]

There you go. Yah baby, IntellifloXF! (EXtra Force?) With that setup, you could also reverse the flow on the slide and launch your kids into the neighbor's pool!

 

[brandon#]

There you go. Yah baby, IntellifloXF! (EXtra Force?) With that setup, you could also reverse the flow on the slide and launch your kids into the neighbor's pool!

Haha! I can just see them being launched down and skipping like a stone across and out of the pool. “Whoops, I accidentally turned it up to 11”

Lots of great ideas here. All seem to involve another pump and some plumbing reconfiguration. Thanks again!

 

[JamesW]

You should get the Intellicenter to control everything.

Use an Intelliflo XF for the filtration. I would go with the 420 or 520 square foot filter.

You should use a check valve bypass on the heat pump.

The fountains look like they will require a lot of flow.

I would add a second skimmer to provide enough flow for the fountains.

How much flow will the fountains require?

Use an Intelliflo XF for the slide on its own plumbing.

 

[Dirk]

@brandon#, is that large statue-thing in the middle of the pond also a water feature, about six feet tall?

@JamesW, did you mean to say two Intelliflo XF pumps, one for the filtration and another for the slide? Why XF for filtration, because of the two fountains?

Of these water features, how would you divide them up between the two pumps:
- main pool filtration
- "pond" filtration with three spill-over waterfalls (and possibly a fountain in the middle)
- two bubblers
- two fountains
- slide

 

[JamesW]

@JamesW, did you mean to say two Intelliflo XF pumps, one for the filtration and another for the slide? Why XF for filtration, because of the two fountains?

Correct. One for the filtration and one for the slide.

The XF is a better pump. Might as well have matching pumps.

The filtration will also need a lot of flow if it's going to provide flow for 5 fountains.

The suction will have to be more than a single skimmer. I would go with 2 skimmers (60 gpm max each skimmer) and maybe a main drain set if the flow needs to be greater than 120 gpm.

 

[JamesW]

I would probably run a line from the Slide pump to the Pond so that I could send water to the pond from either pump.

The slide pump would be able to send water to the slide or the pond or both.

The sheers need filtered water. So, they should go through the filter.

 

[jimmythegreek]

You are installing a fiberglass pool which is in amd backfilled but no deck yet correct? If that's the case you have 2 options. Either wall drains or additional skimmers or combination of both. If using pentair you want am additional intelliflo XF coming from a 3" line to the pump. Wall drains need to be dual VGB compliant. I see bubblers amd sheer descents in the rendering can you list what size they are amd what pipe is going to them

 

[Dirk]

@brandon#, with @JamesW and now @jimmythegreek, you've got two of our best experts weighing in on your setup!