Question about pressure/head/flow rates for new pool

[puppycrack]

Question about pressure/head/flow rates


New pool being built in upstate NY:


18x36 rectangle, 6' deep end. ~21,000 gallons. Pool is ~65' from equipment pad. Would like turnover in the 6-8 hour range, so 50-60gpm for filtering.


SUCTION
(1) 2" line from double main drain
(2) 2" lines from two skimmers


RETURNS
(1) 1.5" line to return on stairs
(2) 1.5" lines to two returns in pool
(1) 1.5" return to double jets in swimout area in deep end


PUMP(s) under consideration
- Pentair Superpump VS
- Pentair Intelliflow VS


Filter under consideration
- Pentair Clean & Clear Plus, 420 sq ft cartridge filter


Heater
Pentair MasterTemp 250k btu


Future
Solar on roof, two stories above




QUESTIONS
1) Would the flow rate through this setup be in the recommended 6-8fps? I am having a hard time coming up with the head calculation / flow rate with multiple parallel runs.
2) Would the flow rate and pressure be sufficient to keep check valve closed on solar?
3) Regarding the pump, I'm liking the Intelliflow's ability to interface with automation, which I may do down the road. But is it way too much pump for this pool? Would it be an inefficient pump to use?
4) Does this appear to be a good setup? Any changes or other recommendations?


Thank you!


- pc

 

[mas985]

Would like turnover in the 6-8 hour range, so 50-60gpm for filtering.

Why? There is no reason to "turnover" a pool any number of times. Head and flow rates really don't matter for general pool maintenance. The only thing that really matters is getting enough FC in the pool and having it distributed which usually doesn't take much time at all. Are you manually dosing the pool?

1) The recommended flow rate is as low as you can go while still maintaining decent skimmer. The water needs to travel over the weir door and not around the sides. However, when solar engages, it will require the pump to ramp up RPM.

2) You want the check valve closed? Do you mean when solar is off? Check valves usually have springs so they don't rely upon pressure to keep them closed. However, they do rely on pressure to keep them open.

3) VS pump is never too much for a pool because it is a VS and you set flow rates to anything you want.

4) If the heater is for general heating of the pool, I would go as large as possible (400k).

 

[puppycrack]

Why? There is no reason to "turnover" a pool any number of times. Head and flow rates really don't matter for general pool maintenance. The only thing that really matters is getting enough FC in the pool and having it distributed which usually doesn't take much time at all. Are you manually dosing the pool?

Please bear with me, as I've never owned or maintained a pool. The only knowledge I have is based on about 5-6 weeks of reading online, the majority of time being on these forums. That being said, I keep reading that you want a GPM based on turning over the pool within a certain time frame; the most common timeframe being 8 hours. As for maintaining pool chemistry, the PB is spec'ing out an auto-chlorinator.

1) The recommended flow rate is as low as you can go while still maintaining decent skimmer. The water needs to travel over the weir door and not around the sides. However, when solar engages, it will require the pump to ramp up RPM.

And there's the rub. I am working off plans, not a pool in the ground, and would like to ensure the flow rate is sufficient to properly skim the pool. I'm having a difficult time calculating for all the variables to know *what* the flow rate would be. If I'm moving 60gpm through the plumbing, with the lines specified, will the fps be in the 6-8 range?

2) You want the check valve closed? Do you mean when solar is off? Check valves usually have springs so they don't rely upon pressure to keep them closed. However, they do rely on pressure to keep them open.

Sorry, I misspoke. I was referring to the vacuum breaker in the solar panels. As I understand it, you need a certain pressure to maintain closure, and I was uncertain if the flow rate / pressure would be enough to do so.

3) VS pump is never too much for a pool because it is a VS and you set flow rates to anything you want.

But wouldn't a higher HP pump, moving a certain GPM, require more electricity than a smaller HP pump moving the same GPM? Or is the dfifference so negligible that I shouldn't worry about it?

4) If the heater is for general heating of the pool, I would go as large as possible (400k).

Thank you for the input. I'll do some further investigation on this.




Thank you for the input. Your insight and knowledge are most appreciated. I have read your Hydraulics post many times, and am still wrapping my head around everything in there.


- pc

 

[Pool Tool]

Just my opinion, but if you have spent 5-6 weeks reading here and still plan to use an auto-chlorinator you've been reading the wrong articles. Even with your short swim season, you might benefit looking a salt (SWG) or Stenner injection system. Turnover and FC levels independent of CYA levels are older schools of thought. Since both of your pump options are VS you can be less concerned about where you would fall in a traditional pump curve.

Here is a simple pipe flow calculator. I did not vet the results, but they seem reasonable. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwi78fiw0K7UAhVM7IMKHTCkA7oQFggoMAA&url=http%3A%2F%2Fwww.calculatoredge.com%2Fmech%2Fpipeline%2520velocity.htm&usg=AFQjCNH2TacOncV6-koixOV1wjg1IjfpJg&sig2=8HnKZ-iiZd3GvWfhepY_gA

I am sure Mark may have more comments, but I just wanted to note those couple of items. I think all your questions are good, but with the advent of VS pumps a lot of these issues are moot. Best of luck to you and certainly don't stop asking questions as we all learn something everyday.

 

[mas985]

That being said, I keep reading that you want a GPM based on turning over the pool within a certain time frame; the most common timeframe being 8 hours. As for maintaining pool chemistry, the PB is spec'ing out an auto-chlorinator.

That is a myth. Just ignore that. You might want to read this: Pool School - Determine Pump Run Time

Auto-Chlorinate as in Trichlor pucks? You should pick any other method than that. Trichlor adds CYA which can build up over time and causes most of the pool issues we see. Other methods include SWG, manual dosing, peristaltic pump, Liquidator.

Sorry, I misspoke. I was referring to the vacuum breaker in the solar panels. As I understand it, you need a certain pressure to maintain closure, and I was uncertain if the flow rate / pressure would be enough to do so.

Yes, that is true. But you can set the pump RPM to make sure that happens. With two speed, you generally have to run at full speed.

But wouldn't a higher HP pump, moving a certain GPM, require more electricity than a smaller HP pump moving the same GPM? Or is the dfifference so negligible that I shouldn't worry about it?

So what really matters is a pump's head curve and the RPM setting. Flow rate is proportional to RPM so with a VS, you can set the flow rate to be anything you want which makes a VS pump "variable size". Yes, a higher HP pump may have a higher MAXIMUM flow rate but that doesn't mean you have to ever run it at the maximum. Most people never do. The maximum flow rate you set for a VS pump is entirely up to you and the requirements of the pool. So it really doesn't matter if the VS is 3 HP, 1.5 HP or anything else.

 

[Jimrahbe]

pc,

If automation is in your future, then the IntelliFlo is the only pump for you. The IntelliFlo was designed to be controlled by automation, but the SuperFlo was not.

It is my understanding that 3 HP IntelliFlo is more efficient at low speeds than the SuperFlo, but either way I doubt you would be able to tell the difference.

For reference, I can run my IntelliFlo, 24/7, for less than $20 bucks a month.

You are just making things much harder on yourself than they need to be...

Thanks,

Jim R.

 

[puppycrack]

Just my opinion, but if you have spent 5-6 weeks reading here and still plan to use an auto-chlorinator you've been reading the wrong articles. Even with your short swim season, you might benefit looking a salt (SWG) or Stenner injection system. Turnover and FC levels independent of CYA levels are older schools of thought. Since both of your pump options are VS you can be less concerned about where you would fall in a traditional pump curve.

I have been focusing my research on what goes underground, and overall pump plumbing. I figured anything on the pad can be changed out if need be, but what's underground is a done deal for the most part. I've ruled out SWG, since I'll be using a steel wall pool with concrete pad, and it doesn't seem the two have the greatest compatibility. Thank you for your comment though, I have much more to learn.

- pc

 

[puppycrack]

Auto-Chlorinate as in Trichlor pucks? You should pick any other method than that. Trichlor adds CYA which can build up over time and causes most of the pool issues we see. Other methods include SWG, manual dosing, peristaltic pump, Liquidator.

I have some learning to do

So what really matters is a pump's head curve and the RPM setting. Flow rate is proportional to RPM so with a VS, you can set the flow rate to be anything you want which makes a VS pump "variable size". Yes, a higher HP pump may have a higher MAXIMUM flow rate but that doesn't mean you have to ever run it at the maximum. Most people never do. The maximum flow rate you set for a VS pump is entirely up to you and the requirements of the pool. So it really doesn't matter if the VS is 3 HP, 1.5 HP or anything else.

So if I understand correctly, I really shouldn't worry about the plumbing setup too much (3 suction, 4 returns). I just dial the pump to get the desired flow rate, and let the GPM be whatever it is?

 

[AftonJeeper]

I have the same plumbing you do (3 suction, 4 returns) and the same equipment but my pool almost twice as big. I run my pump less than 12 hours a day now. You just need to keep it balanced.

My PB added the auto-chlorinator to my pool (before I knew better), save your self the money and don't get it installed.

 

[Teald024]

So if I understand correctly, I really shouldn't worry about the plumbing setup too much (3 suction, 4 returns). I just dial the pump to get the desired flow rate, and let the GPM be whatever it is?

I don't think any comment above were about your suction & returns. Having those multiple suction and return lines will help keep the pool more evenly balanced.

The items discussed above were about the pump itself, head and the "turnover rate". With the VS pump, you adjust and tune in the speed and time based on the chlorine needed, heating and the water quality (filtration & skimming) needs, any water features, etc. The flow rate is what it is.

.

 

[Teald024]

So it really doesn't matter if the VS is 3 HP, 1.5 HP or anything else.

Can you run through a "what if" for me. Lets say I'm on Amazon about to buy a pump. I have to pick a power rating. Which one do I pick? 3hp seems overkill because I don't have any special features except solar collectors on a 2 story house. I may make the assumption that 0.5hp is too small. SO is 0.75 / 1 / 1.5 / 2 hp enough? How do YOU know which rating to select so that I can get that nice fuzzy feeling in my belly? I wouldn't want to buy a pump that was too small. This is where I would try to look up head vs flow curves and see which one matches my needs.
Are you giving advice above about the IntelliFlo knowing that it only has one motor power rating? In this case it's a no brainer because there isn't a choice. I think a lot of people come here asking about head & flow calcs because they don't know any other way of selecting a power rating.

Break this out to a separate thread if you think its warranted. I don't want to hijack this OP's questions.

 

[mas985]

I may make the assumption that 0.5hp is too small.

Why? I use a 1/2 HP on low speed nearly all the time and have a larger pool than you. I also ran solar with it on a two story house but mostly on high speed. But you won't find a VS that small anyway.

I wouldn't want to buy a pump that was too small.

Nearly impossible unless you are running a spa or high flow rate water feature. Intex is probably the only pump that I might consider too small although it works fine for some pools.

I think a lot of people come here asking about head & flow calcs because they don't know any other way of selecting a power rating.

Selecting a pump for just circulation and filtering is easy. Just get the smallest possible and at a minimum, a two speed.


My point is that for general circulation and filtering, HP doesn't matter. Although the lower the flow rate, the better filters seem to work. It only makes a difference in high flow rate or high pressure applications. However for cost, it may make a difference and that is what I would probably go by. Also, pumps like the Intelliflo have a few more features than the Superflo VS and to some that is important and worth spending a few more bucks on.