VS Pump speed

needsajet

TFP Expert
LifeTime Supporter
Jan 4, 2016
4,918
Sydney, NSW, Australia
Pool Size
44000
Surface
Plaster
Chlorine
Salt Water Generator
Kevin, I forgot to mention, in response to your concern about the pressure loss through the filter... the pump does 'work' to run your system, and that includes three main things (if you had water features, that would be additional 'work' to create aesthetic or other effects).

One part of the 'work' is to filter the water, one is to make the water in the pool move, and one is to overcome friction inside pipe and fittings. Filtering is a big part of the 'work', pushing water through small pore spaces, to catch the small floaties and make your water crystal clear. It's part of the job, and not alarming in any way, until the filter gets too dirty for the system to do a good job, at which point it gets backwashed.
 

needsajet

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So, you have to add the suction side to make up the difference.
It seems reasonable to me that Pentair would include an allowance in their logic, but perhaps not. I also recognise that if they did, it would likely be based on 'typical' installations, and 6' of lift would be atypical. Having a markedly different approach to measuring pressure in a pool circulation system seems as though it would be confusing and harder to sell.
 

DeanP66

Well-known member
Mar 26, 2014
1,191
San Jose, CA
Don't forget the heater as well. If you've got something rattling around in there, there could be quite a bit of water restrictions going on. Another option is to install a heater bypass with a 3 way jandy valve on the pipe coming out of the filter heading to the heater input and then install a check valve on the pipe coming out of the filter.
 

JamesW

TFP Expert
Mar 2, 2011
24,836
It seems reasonable to me that Pentair would include an allowance in their logic, but perhaps not.
The system only measures power and then it gets the flow from this chart.

Once it has the flow, it plots the flow on the pump performance curve to find the total system head loss.

It has no way to allocate the head loss between the suction and return.

1623118203823.png

watts......GPM.....Head loss in feet
1,500.........12...........94
1,750.........28............93
2,000.........44...........90
2,167........57............88
2,333........67...........86
2,500.......79............83
2,750.......95...........78
2,900....115...........70

 
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needsajet

TFP Expert
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Jan 4, 2016
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Sydney, NSW, Australia
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Your equipment pad looks really good by the way. One thing I noticed is white PVC valves. In my experience, white PVC valves kept out of the sun are usually fine, but when they get long-term sunshine on them they can get stiff. Some that are never turned will jam up and people break the handles trying to get them to move. Yours are the better ones that can be disassembled, and hopefully never have this problem. Keeping sun off the equipment will help it stay looking good and last longer, if that's an option. Painting white PVC pipe and fittings is also popular.
 

Sollace

Gold Supporter
Aug 16, 2020
538
Bryan TX
Late to the thread. . .
The conversation went from flow rate trouble on a new pool to test kits. . .

Our pool is also new. When we added salt. No. When our pool build rep added salt, he dumped in too much. I think it was 4400 via my Taylor Salt test kit. !! On a new pool, I worried, so we dumped about a foot of pool water and got our number down to 3400. The reason I bring all this up is when we turned our system back on, the pumps moving freely, they "spit" out some chunks of plaster that were stuck. I assume some of the wet plaster got pushed in the openings, drying, and jamming.

So I thought of all that when you mentioned flow rate on a new pool. Maybe something similar. We didn't find that out until we did that water dump to lower our salt level. Completely unexpected.
 

needsajet

TFP Expert
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I assume some of the wet plaster got pushed in the openings, drying, and jamming.
I had this problem on our new pool as well. I did most of the plumbing myself, and the builder thought I was nuts when I back-flushed all the lines before finishing the connections, until he saw all the debris that came out, lol. Everything had been taped up, but shooting the pool and plastering is rough work.
 

KevinBond

Well-known member
May 7, 2021
100
Kitchener, Ontario, Canada
Pool Size
71000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I'm also very grateful for all the advise here! I have learned so much in the last few weeks!

I haven't yet had a chance to open the heater and take a look - hopefully this weekend.

I'm having trouble finding a vacuum gauge here in Canada, would any of these work (I don't know if they would even fit in the drain plug hole on my pump)? They look to be mostly for measuring air pressure.

Also having trouble finding a flow meter and... installing looks like it would be outside my comfort zone.

Seems like the current theories for my high pump RPM are one or more of the following:
  1. suction issues (per @JamesW)
  2. pump giving inaccurate GPM readings for RPM (per @needsajet)
  3. heater restricting flow (per @DeanP66)
That seem correct?

For the inaccurate readings: I found my SWG stops working at ~15 GPM according to my pump. My manual says the minimum is 20/25 (it says both so I'm not sure which is correct for my model). Is there a generous +/- in there or can I assume my GPM is 5-10 higher than what my pump is telling me?

Complete long shot but when I first filled the pool (last September) I had a ton of while flakes coming out of the returns (I've seen no flakes since opening the pool last month). Our water is very hard and my PB said it was calcium (I believe) extracted from the water by the SWG. Could that have caked up things causing flow/suction issues?
 
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JamesW

TFP Expert
Mar 2, 2011
24,836
That's a pressure gauge, you need a vacuum gauge.

It should look like this with the needle starting on the right and going counterclockwise which is the reverse of a regular pressure gauge.


1623366781634.png
 

DeanP66

Well-known member
Mar 26, 2014
1,191
San Jose, CA
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needsajet

TFP Expert
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Jan 4, 2016
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Sydney, NSW, Australia
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I have the flow vis on my own pool, but not on the other pools. Many here at TFP regard the flow gauge as unnecessary, because everything needed to know in terms of flow, which isn't much, can be determined other ways, and I respect that perspective.

That said, it's very handy being able to glance at the flow and pressure and instantly know... for examples: skimmer has more debris in it than I prefer to allow, or filter can go a while longer before backwashing, or I forgot to increase flow to one branch of the return side. But main one of all, is that it's instant to know that the filter actually does need backwashing, and pressure only looks normal because I haven't cleaned the pump basket for way too long, and suction potential is reduced.

Others might see that as "your SWCG will indicate low flow before that happens anyway" which is also true.

So there's both sides. On a needle of 1 t0 100, I'm at around 75 or 80 in terms of liking having my FlowVis flow meter.

We can teach you the PVC plumbing and it's only a teeny bit harder then everything else you've already done. It's actually super easy on your system because your plumber has been kind enough to use lots of unions and also valves that do double-duty as both unions and valves.

The flowvis cost me a lot more here than USA prices, likely same hurdle as it is for you, but I'm pretty happy to have it. I think it's more helpful with variable speed/flow pumps. For single speed there's less gained from a flow meter. The other pools I care for are all single-speed, and I don't miss the flowvis very much.
 
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JamesW

TFP Expert
Mar 2, 2011
24,836
That should work and it will will be worthwhile to install.

Do not overtighten the gauge or the hole can crack.

Use some Teflon tape and some sealant and get it snug but not super tight.
 
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KevinBond

Well-known member
May 7, 2021
100
Kitchener, Ontario, Canada
Pool Size
71000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
That should work and it will will be worthwhile to install.
Perfect, I'll order that one. I measured the distance from the drain plug on my pump to the concrete and there should be plenty of room (I shouldn't have to lift the pump up as you suggested might be required).
 
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KevinBond

Well-known member
May 7, 2021
100
Kitchener, Ontario, Canada
Pool Size
71000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I'm going to switch my pump settings from GPM to RPM as almost everyone here has recommended. This means the pump will always sound the same (won't get louder over time as it does now) - is that true? My understanding is the flow rate will just decrease as the filter gets full.

I think this was a major factor in my stressing about this. I'd hear it slowly get louder each night and I'd lay awake fretting about it... :confused:

Couple questions regarding this:
  1. Will the filter gauge behave the same? Right now, when I backflush, I reset to "start" and know to backflush again once it gets close to "dirty".
  2. Assuming I choose a low RPM, as the filter gets full, the pump will stop providing enough GPM to activate the heater/SWG. Is this perfectly fine (no risk of damaging either or safety concern)?
  3. (related to above) I just want to confirm my heater has a low flow safety shutoff. What happens if the heater tries to turn on if there isn't enough flow? Will it just do nothing?
 

DeanP66

Well-known member
Mar 26, 2014
1,191
San Jose, CA
I'll let others chime in on the heater question since I have no experience with one, but the SWG will just stop producing chlorine because the flow switch won't close fully. That is usually why we recommend finding your minimum rpms to close the flow switch with a clean filter and then add 200 or so. That takes into account your flow rate slowing down some as your filter gets dirty.

It's a good idea to monitor your SWG to make sure no unexpected lights are on. I usually like to walk to my equipment pad and look at the controller once a day just to make sure everything is kosher.
 
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