Confused about reconciling GPM ratings and standards.

[mvoltin]

Starting to build a new pool (actually, halfway done) and having trouble reconciling piping recommendations based on GPM.

Based on what I have read, 2" piping only supports around 80GPM (or 63GPM on suction and 84GPM on return side). There are other small variations across websites but its universally somewhere around 80GPM but more conservative would be to aim around 63GPM (based on suction side).
Numbers for 1.5" are around 35GPM suction and 50GPM return.

QUESTION:
Pentair 1.5HP VS pump https://www.pentair.com/en/products/pool-spa-equipment/pool-pumps/superflo_vs_variablespeedpump.html#specifications can go up to 100GPM (see the picture from brochure below), yet, it has unionized fittings of 1.5" and 2" based on the installation manual. I called Pentair and was told the actual opening is 1.5" - so, it should support up to 50GPM from everything I have read. They couldn't provide any reasonable explanation ("that's how it is").

Can anybody help explain what I am missing? Why pump rated above 80GMP has fittings less than 2.5"?

Thank you.

P.S. I have cartridge filter that is rated up to 150GPM and it has 2.5" fittings.

https://www.pentair.com/en/products/poo ... 181411.png

[Teapot]

Hi mvoltin,
I do agree to a certain point that pool companies build rubbish products that are not effecient, they counter this lack of efficiency by stapping on a large pool pump so no matter how bad the system is water will arrive where it should. This cost the consumer and the planent but pool companies don't seem to care and their designers, if you can call them that are just opying other manufacturers rather than innovation. (big powerful pumps does seem to appeal to the male ego)

Now that said why on earth do you want to try and achieve such a high flow rate? The first thing I do with a client's pool is put my flow meter on it to see what the flow rate actually is and it's usually half whet the pump and filter spec says. look at my pool spec, 63mm pipe (just a bit bigger than 2". 70 watts of electricity = about 0.06hp on filtration around 1800 rpm of the pump, 1800 gallons per hour flow rate which gives a turnover of 6 hours for my pool and the pump runs 24 hours to give 4 turnovers per day. The cost of my system running 24 hours is about the same as a similar convetional pool running for 2 hours so loads cheaper to run and slower flow gives better filtration, not that you'll notice if you use a cartridge filter but who knows, maybe you will.

[mvoltin]

Thank you, Teapot.

That is really sad to hear. I guess the performance charts are like manufacturer advertised car gas mileage, only worse.

To answer your question about the flow requirements - I really tried to read up and go by standards as much as I could:

My pool has 10 waterway jets that require 10GPM each (https://waterwayplastics.com/manuals/810-0023.0916.pdf) and very small dynamic head with 2.5" piping. I will probably run the jets couple times a week for an hour or so. Otherwise, my flow requirements are very small. Strictly based on the Pentair pump performance chart, it could have exactly met my needs for both max and minimum flow. (I was willing to "close up" one or two jets to bring the total flow requirement down to 80GPM)

Based on what your observation that actual flow rates are about half of what's advertised, then I am in trouble and may have to go with two separate pumps or larger pump. It just doesn't make sense to get 3HP for my pool that is not big and only requires around 20GPM 95% of the time. I was just really hoping to get one VS pump and dial the speed up when needed.

[Teapot]

Hi mvoltin,
I understand what you are doing better now, a swim spa with massage jets?

I re engineered a couple of commercial spas as the filtration suffered badly when the high flow spa was switched on. I separated the filtration from the spa jets so proper slower flow rate was maintained through the filtration which saved money and reatly improved water quality. The spa jets were set up via a second pump and an air operated switch.
On a smaller spa I just used a 2hp spa air blower with a hot air heater after the blower which was very nice to use.