A brief experimental confirmation of pump RPM, flow, and current (cost) relationships

[HermanTX]

These are great insights, and much appreciated. One question for these low-flow speeds: do you guys close off your deep end drains in order to boost the flows into the skimmers? I have two skimmers and a double main drain, and have previously left them all open except when manually vacuuming.

I have a 3-way valve between my skimmers and my main drain (my skimmers are plumbed into 1 line unfortunately). So, I turn my 3-way valve with about 20% open to main drain and full open to the skimmers.
I always like having some suction from the main drain because if a weir door would be suck then there is always fluid suction from the main drain, so the pump does not suck dry.

 

[Sampo]

I turn my 3-way valve with about 20% open

That's very interesting and helpful. I have Jandy 3-way valves. But I had assumed that they operated like a "3-way stopcock" and could only be left in either a fully-ON or a fully-OFF position for each of the ports (at least for prolonged periods). Similarly, I've heard that ball valves in home plumbing should not be left partially open. I wonder if I need to confirm whether my specific Jandy valves are rated to do this partial flow-limiting operation?

 

[ajw22]

. I wonder if I need to confirm whether my specific Jandy valves are rated to do this partial flow-limiting operation?

Confirm with who? Others who pass on myths about valve settings?

Set your diverter valves or ball valves whichever way works best for the application.

Ball valves and other valves are often put partially open to throttle water flow and pressures.

 

[Sampo]

Ha ha! Sounds good to me! This is why I love this site -- it's like watching MythBusters, but way more practical!

 

[wireform]

Ha ha! Sounds good to me! This is why I love this site -- it's like watching MythBusters, but way more practical!

Pay in advance
Become a TFP Supporter
and TIA.

 

[generessler]

Is this from the pump's display?

It's mixed 2" and 2.5" plumbing, 4 return jets, 2 skimmers, main drains, a flow gauge, a heater bypass, and a 330 sf cartridge filter. At 1200 rpm the pressure is just about unreadable. Maybe 2 psi. It's true that if I disable the bypass, flow goes way down. That's why I normally have the bypass enabled.

 

[Sampo]

Become a TFP Supporter
and TIA.

Just did. This site is awesome, and I'm so grateful for this community.

 

[Sampo]

At 1000 rpm it looks like he'd see 20 gpm. That's pretty low for skimming.

Do you have a benchmark for the minimum acceptable flow? Or is this different for each pool -- and determined by having anything enter the skimmers and a "good enough" look to the pool?

 

[mas985]

The best criteria is if there is enough flow rate to pull down the weir door so that water travels over the weir door rather than around the sides. This maximizes surface velocity and ensures that more debris will travel in the skimmer rather than around it.

I know from my own experimentation, my two Renegade skimmers need about 26 GPM total to keep the weir door down which is about 13 GPM for each skimmer.

However, it does depend some on the design of the skimmer as to how much flow is required so your results may vary.

 

[Newdude]

Just did

THANKS for extending the date the lights go out.

We're all volunteer here and don't have a dog in the fight, but that doesn't mean we want to have to find a new hobby. It might involve running.

 

[generessler]

Do you have a benchmark for the minimum acceptable flow? Or is this different for each pool -- and determined by having anything enter the skimmers and a "good enough" look to the pool?

It's pool specific. It needs to be enough to actuate the flow switch of any equipment that has one - SWCG and heater for example - and the schedule as a whole (including possible higher rpm periods) needs to get floating cruft into the skimmers. If you run through the winter it also must open all check valves to avoid freezing. And of course you need to be content with the amount of random particles in the water that haven't yet been filtered out, though if you choose to run 24/7 thats almost certainly no problem.

That said, threads here that I've been seen have reported low speed of 1000 to 1500. I run 1100 summer, 1200 winter, with a couple of hours morning and evening at 2200 for skimming and pressure side cleaning.

 

[Newdude]

And of course you need to be content with the amount of random particles in the water that haven't yet been filtered out, though if you choose to run 24/7 thats almost certainly no problem.

The suspended particles plague us all. In the couple of days it takes for all the barely moving 'floaties' to find the skimmer, it was breezy again and more blew in making it seem like the originals weren't filtered.

Theoretically more flow means a better chance of the water being filtered faster but more flow also stirs it up more, letting the floaties stay where they were.

 

[BMerrill]

Consider investing in a BETTA surface skimming robot. Runs on solar power. Mine does well except for very fine pollen.