GPM not RPM

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S

sawallach

Member
Jul 13, 2024
5
Pike CA
Pool Size
40000
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
We’ve had our 40,000 in ground for 4 years now and I have finally stumbled across ‘the answer’ for the most efficient use of our Pentair variable speed pumps. If you google what to set them at there are all sorts of discussions related to RPM; set it high, set it low, run it all day, run in short bursts….all very confusing.

I was trying to balance running enough water through the filters and Intellichlor whilst still conserving electricity. Setting an RPM just wasn’t balancing all of those needs….until I realized forget the RPM’s and go with the GPM setting on my ScreenLogic app. It will take care of the RPM’s. After all, it’s all about the amount of water you run through the filters and Intellichlor that keeps your pool sparkling.

After making this revelation and using GPM settings I sleep a lot better knowing the pool is being properly ‘turned over’, pumps are running efficiently for electrical use and algae growth is not a problem.

Here are my settings: I run the pumps from 10pm to 10am at 25GPM. This is the most efficient for electrical use as these are the cheapest hours for kw’s. During the day, if the pool is being used, I ramp the GPM up to 60 as this maximizes the water running through the skimmer (especially helpful when the German Shepards are playing fetch) and increases chlorine output. Every once in awhile I will SuperChlorinate during these periods for an added boost on hot days. Running at a high GPM during these periods is also beneficial as electrical use is entirely provided by our solar.

So far, other than having to add some acid every so often in order to bring down the pH (a common side effect to a salt water pool) the GPM method seems to be the way to go.

My new mantra is GPM not RPM!
 
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Welcome to TFP.

RPM not GPM.

Turnover is a myth - Turnover of Pool Water - Further Reading

GPM hides the fact that your filter is getting dirty and loading up and slowing your water flow. For best electrical efficiency you should be cleaning your filter instead of increasing the load on the pump.

It is not what we recommend but its your pool to run as you wish.
 
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sawallach said:
After all, it’s all about the amount of water you run through the filters and Intellichlor that keeps your pool sparkling.
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Saw,

Your thinking is based upon the myth that you have to turnover X amount of water per day.. This is absolutely not true.

Pools stay clear and sanitized due to the chemicals in the water, not the number of times the water passes through the filter.

The filter is only there to capture the junk that falls into your pool and floats. By the time your filter starts picking up algae, you have already lost the algae war.

We do not care if people want to turnover their water a million times a day, and we don't really care if people want to use GPM vs. RPM. Our goal is to provide the knowledge so that pool owners can decide how they wish to operate their pools and not rely on myths and magic potions..

Thanks,

Jim R.
 
I never said you had to turn the water over every day. What I said was RPM’s are an inefficient way to use your variable speed pumps and monitor your pool chemistry. Using GPM to get water flowing through your Intellichlor, chlorinating your water and still efficiently using the variable speed function on your electric pumps in my opinion is the name of the game. There’s too much discussion out there about RPM’s that is confusing and really wasted effort. Whether it’s RPM or GPM it’s all about flow. I’ve found that GPM is the better balance for flow and electric usage.
 
Jimrahbe said:
Saw,

Cartridge filters should last 8 to 10 years..

There is no such thing as 'minimal' algae production.. You either have algae or you don't.. :mrgreen:

Thanks,

Jim R.
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That’s right, and I don’t have algae. Are you suggesting that I leave my filters in for 8-10 years. I think not. What I do do is swap my filters out, clean them and set aside for the next swap out.
 
Saw,

Sorry, when you said "Swap out filters" , I took that to mean you were installing new filters every 90 days.. :(

I clean my CCP-520 once a year.. My filter pressure if about 1 lb. on a 30 lb. gauge.

I run my 3 HP IntelliFlo pump 24/7, mostly at 1200 RPM for less than $20 bucks a month. This is plenty of flow to run my SWCG and Skim the pool well.

This is what works best for me.. You should do whatever works best for you.

That said, the way I run my pool may not work for others, and the way you run your pool may not work for others. There are many different kinds of pools and pool owners, and we just try to provide info so that those pool owners can decide how they wish to run their pools..

Thanks,

Jim R.
 
sawallach said:
What I said was RPM’s are an inefficient way to use your variable speed pumps and monitor your pool chemistry.
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RPMs are the way that many of us use our pumps, and it can be very efficient. It is also easy to maintain water chemistry.

You run your pump for a reason. Mixing, Filtering, adding chlorine, heating, skimming etc.

Many of us run low RPM, typically using RPM at cell shutoff + 200 rpm, to protect from a dirty filter turning off the no flow switch on the cell. This is the cheapest way to run. Lower RPM is lower electrical cost. Will make chlorine if you have SWCG, and will mix any chemicals you add to the water. For my pool, I run 24/7 at 1400 RPM. Filters fine, skims fine. For others, if they don't get enough skimming, then we would increase our RPM until we get the skimming action we want, for whatever period.

The one area where GPM become critical is with a gas heater. Most heaters have a minimum flow requirement. I have a flow switch for my heater set at minimum flow. It happens that I get minimum flow for the heater at 2200RPM. When I want to heat, I run the pump at 2200 RPM.
 
sawallach said:
What I said was RPM’s are an inefficient way to use your variable speed pumps and monitor your pool chemistry.
Click to expand...
It's like MPH and KPH. They mean the exact same thing and you're either going 60 MPH or 96.5 KPH. People will argue all day about that too, but the vehicle is moving as fast as it's moving either way.

My pump reports RPM. To calculate it to GPM, to then raise or lower RPM accordingly is just silly, so I learned to speak RPM instead.
 
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Newdude said:
It's like MPH and KPH. They mean the exact same thing and you're either going 60 MPH or 96.5 KPH.
Click to expand...

It really is not because the VS pump controller is regulating the motor with different parameters.

We have seen where pumps will pressure limit GPM speed and you can get more flow from running with RPM then GPM.

Pump controllers directly measure RPM. GPM is a derived value and not directly measured.
 
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I’m just one guy who never was able to get a straight answer on an efficient RPM value to save electricity and provide good chlorination. This is not my first rodeo with pools but this is by far the largest pool I’ve ever dealt with.

Initially I went with the installers recommendation of 2500RPM for half a day (he of the turn the pool over myth.) When I started seeing my electric bills I went there’s gotta be a better way with the VS pumps. I did a lot of research and everyone talked about RPM’s, fast/slow, 6, 12, 24 hours there seemed to be no practical guide so I started doing my own experimentation.

The outlier in all this is my utility’s peak pricing and how to work around that with pump operation and chlorination. There are obviously hours I don’t want to be operating my pool pumps because it is extremely expensive. To start I went the low RPM route and immediately ran in to algae problems. Then I went to high RPM’s for short bursts, same problem with algae. Finally I started to play around with GPM and correlating what it said for RPM’s. As I watched the pump with a set GPM, the RPM’s would vary according to, I assume, the demanded GPM. Eventually I came up with what works for me.

Basically I’m dosing chlorine to the pool using a low GPM which correlates to a variable low RPM for 12 hours. This seems to keep algae in check and provide enough free chlorine during the day if the water is not churned up by people (or dogs). If not, I run at a higher GPM to get more water through the chlorinator during the day when there’s more burn off.

I never thought my post of GPM vs RPM would be so controversial 🤪 Like I said, I’m just one guy who found what works for my pool.
 
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sawallach said:
To start I went the low RPM route and immediately ran in to algae problems. Then I went to high RPM’s for short bursts, same problem with algae.
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Sounds most like a chemical issue than an rpm issue.

Tell us a bit more about your pool by filling out your signature with pool, all pool equipment (including manufacturers and model numbers) and test kit info.
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Also add pool info to your account details so they show under your username and icon.

Are you following the FC/CYA Levels chart?
 
I run my pool on off peak hours only from 9pm to 9am. The first 4 hours are at high speed (~3500) and the last 8 are at low speed (~1300.) The T-15 salt cell had no trouble generating enough chlorine while set to 50%. When we first put the VSP in it saved us $30/mo over the single speed we had before. One of the perks of this is when there is any hint of a freeze here in Phoenix (yes, we sometimes get them though not like we used to) I know the pump is running all through the lowest temps.
 
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