Pool plumbing question (1.5" to 2")

[mas985]

Once you open the pool, you can confirm the filter pressure but with what you have told me and a target of around 17 PSI, here is what I get from the hydraulics model:

Current setup

75 GPM @ 54' head, 1800 watts, 2.52 Gallons/watt-hr

Changing only the pad plumbing to 2"

87 GPM @ 45' head, 1920 watts, 2.71 Gallons/watt-hr

Changing all plumbing to 2"

90 GPM @ 43' head, 1960 watts, 2.76 Gallons/watt-hr

Gallons/watt-hr is the primary metric I use for efficiency so changing the pad plumbing gives you about 7.5% more efficiency. Replacing the suction and return lines only about 2% more. But this assumes that all of the fittings and valves are changed with the pipe.

[VikingKnut]

Thanks Mark for all your analysis. Quick question, since I only run my pool for 4 months out of the year, do you think there would be considerable payback by upgrading pad piping.

Also, what size pump would you recommend with existing piping? What size pump with the pad piping upgraded to 2"? How much benefit of a 2 speed pump? Variable speed?

Thanks.

[mas985]

For cost, one turnover per day would require about 7 hours @ 1.8 kw with your current pump and plumbing but only 6 hours @1.9kw with a pad change. So a monthly difference of 36 kwh or 144 kwh per year savings. Multiply that by your utility rate and you can get the savings per year. Even at the higher energy rates, it is probably not worth the trouble.

For pump sizing, the smallest SuperPump is a 1 HP uprated pump two sizes down from what you have and would provide about 60 GPM on your plumbing or about 2.7 turns per day. Fixing the pad plumbing would bump that up to 68 GPM or over 3 turns per day which is plenty.

Another option would be to just replace the motor with a two speed motor. If you ran on low most of the time (2 hours high, 10 hours on low), you could save about 550 kwh per year. Still not a lot but could pay for the motor in a few of years.

If you normally run 2 turns per day just double the energy savings.

[BigBessey]

I know this is an older post but I'm considering a similar upgrade and trying to determine if it is worth it. Pool is 16'x32' roughly 20K gallons I believe. I have a new Pentair Superflo VS variable speed pump Model 342001. All of my eyeball fittings are the flexible nozzles that change diameter as the pump speed increases.

The pool has two 1.5" suctions lines (one from the bottom drains and one from the skimmer) that come above ground to a hard tee then go into the pump with 1.5" piping. The entire system is 1.5" piping then it splits off to two 1.5" zones of return jets (one that has 2 jets at the steps and one that has 4 jets at other locations).

I'm an engineer type and I would have thought the improvement going from 1.5" to 2" for the above ground piping would be dramatic. Those tees seem like a serious choke point.

[PoolDoc]

If you are an engineer type, you might be better off using some of the free online pipe and flow calculators to do your own rough hydraulic analysis. There are a bunch of them out there.

But, it's hard to do, with residential gear: the piping is no problem, but the supplied equipment flow data range from poor to unavailable.

I've done such calculations many times, but for large commercial pools. When I tried, this spring, to do them for some idealized residential pool / pump / filter combos, I was stymied by the lack of meaningful data.

I suspect some of this is deliberate: the VS pumps are often way, way too big for the piping or filters with which they are coupled. And when they are occasionally, even by accident, run at full volume, they are bursting pipes and valves, splitting filters, destroying cartridges, and back washing sand out all over the ground.

Obviously, that's not something for which the pump makers want to stand up, and take the credit!