Dual versus single skimmer at low pump flow rates

rlab

Well-known member
Oct 4, 2019
69
Australia
Planning a mediumish size (26' x 10') pool, PB is recommending dual skimmers due to nearby trees. Was trying to get my head around how this impacts variable speed pump use, as flow rate is now split between the 2 skimmers.

With dual skimmers will I have to run twice the flow rate I would otherwise use with a single skimmer?
Or are 2 skimmers at lower flow rate as effective as 1 skimmer at higher flow rate?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,584
Pleasanton, CA
With dual skimmers will I have to run twice the flow rate I would otherwise use with a single skimmer?
Or are 2 skimmers at lower flow rate as effective as 1 skimmer at higher flow rate?
Both can be true. It depends on the flow rate settings.

There is a minimum flow rate for a skimmer below which the water does not flow over the weir door so skimming is not effective. If you operate the pump such that the flow rate is at the minimum for each skimmer, then two skimmers will require 2x the flow rate of a single skimmer. However, if you operate at a flow rate well above the minimum flow rate for both scenarios, then the two skimmers will just skim at a slower rate than the single skimmer.

But the energy use differences may not be that large between one and two skimmers. I have two skimmers and have the set RPM such that the flow rate is near the minimum for each skimmer. The energy use is only 110 watts. At half the flow rate, assuming only a single skimmer, the energy use would be 36 watts. Even at 110 watts and $0.40/kwh in our top tier, is not that much for a 6 hr run time (~$8/mo).
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
18,225
Bedford, TX
R,

I would also think that the size of the pump enters into the picture.. For reference, I have two skimmers and a 3 HP IntelliFlo that I runs at 1200 RPM most of the time. At that speed the pump uses about 180 Watts of power and both skimmers and my SWCG work just fine.. The larger the pump, the slower you can run it and still move a lot of water.

I have a couple of rent house pools that just have one skimmer... My pool has two skimmers and works much better, skimming wise.. Especially when the leaves start to drop.. It is like night and day.

If I build another hundred pools, they will all have two skimmers.. It would be more than worth it even if there were a slight increase in electrical costs.

Thanks,

Jim R.
 

JamesW

TFP Expert
Mar 2, 2011
19,721
I definitely recommend 2 skimmers. The one that gets the most leaves can clog and restrict water to the pump.

With a second skimmer, you reduce the likelihood that the pump will not be able to get good flow.