# Thread: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

1. ## Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

I replaced my old 2.5 Hp pool pump with a pentair 3HP variable speed pump and am working on programming schedule. I've browsed through several threads and cannot find an easy way to calculate my pump flow rate. I know what I need as far as gpm but dont know how to calculate with out installing a flow meter. Is there a simple math problem that can be used. I have a 24000 gallon Pool/spa kidney pool, de filter and Raypak heater.

2. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Welcome to TFP!!!

There is no reason to calculate your flow rate ... and it is not trivial to do so. That is why you can not find an easy way to calculate it.

I think you should take a look at this: Determine Pump Run Time

3. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Welcome!

Nearly everything you need to know for determining RPMs to program can be determined fairly easily experimentally. For example try different RPM settings until you find the lowest speed that keeps the heater happy, and then run a little faster than that when using the heater.

4. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Right. What everyone else said. All sorts of info such as pipe diameter, friction loss factors, bends, turns, leigth, etc come into the equation of flow rate.

The 3 HP is more than big enough, so having the ability to provide enough is not ever going to be an issue. Just figure out the low RPM side, where your pool and other equipment is happy, and use that. The low side is determined by trial and error. I doubt the maximum RPM (flow rate), you may actually need would be more than 1500 - 1700 RPM (if that), while the minimum RPMs might be as low as 900.

5. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Thanks for all the responses and advice read the pump article and also mikes link about pool pump study in florida. I turned on my pool heater and found that it will stay satisfied at 1275 rpms. I played with the settings yesterday, I actually set the pump to run at 1275 rpm for 12 hrs 6am - 6pm. I came home at 3pm and noticed a sheen of debris on the pool surface not removing debris well at this speed will not suck leaves into skimmer basket. I ramped the pump up to different speeds and noticed that at 1800 rpm I can see the debris going towards the skimmer basket more quickly. What is a good schedule to set the pool filtering at, Im thinking 6am - 12pm 2300 rpm avoiding peak energy hours and 8pm -12pm at 950 RPM to clean after pool use. My kids are home all summer and it heats up here in chino ca with average summer temps in the 90s; they will use pool heavily. I appreciate your help with this.

6. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Just to be sure, you have a weir on your skimmer right?

7. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

We are able to get good skimming action at 1100rpm. We have two skimmers and a main drain. Valve is set about 80% skimmers and 20% main drain. Do you have your eyeballs set to promote clockwise or counterclockwise circulation in the pool? Usually, one way or the other does a better job of moving debris around the pool and into the skimmers. A properly operating weir door on the skimmer will make a big difference also.

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Unless you have trees dropping debris in the pool 2-3 hours in morning and 2-3 hours in evening should cover it.

8. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

I read up on the importance of the weir door, I will be checking operation today, apparently the water level must be spot on for the weir door to work properly. My pool outlet ports dont have eyes, not sure what they look like however there are 1" threaded pvc at these outlets are they supposed to have eyeballs? I also forgot to mention my filter needed to be cleaned even before I installed new pump, haven't done this yet. How do you determine when the filter needs to be backwashed, with the lower RPM settings I am barely getting a gauge reading?

9. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

The water level is not that critical for the weir to work. Just needs to be in the skimmer and not too low or way too high.

You need to clean the filter when the pressure rises 20-25% over the clean pressure. You should do this check at a higher pump speed.

10. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Weir doors move up and down with water level and water flow. There is a several inch window that is fine. Pick a speed, like 2500 rpm, and use that as your reference point. When pressure rises 25% from clean at 2500 rpm then it is time to clean.

Here is a big assortment of eyeballs to choose from. I think mine are 1/2".
http://www.sunplay.com/wall-return-and-eyeball-fittings

11. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Thanks again for all the help this is a great community glad I joined. I just serviced my pool filter yesterday I have a 60sq. Ft DE Filter. Removed the filter grids cleaned thoroughly. Placed filter back in service, I charged the DE with the recommended 8 Lbs and only noticed a slight increase in gauge pressure, went from 18 psi to 18.5. Some of the threads here recommend pressure increase of 2lbs is my filter DE undercharged? I ran my pump at 3200 RPM

Also, I ran the pool pump at 3200 RPM to vacuum pool after servicing filter and noticed the suction was not as strong as the day before. I opened the filter air release valve and air and water are frequently pulsating out of valve. I am not seeing a steady stream like before. Do I have a leak somewhere?

Finally, I am looking at purchasing eyeballs to create a good current flow to the skimmer as suggested. What is a good size eye opening, My pools 3 eyeball locations are evenly spaced. Should they all point towards the skimmer or point at each other to make the water circulate in circular motion?

Thanks again for all the help.

12. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

I never see a pressure difference between when first starting the clean filter and adding the DE.

All the air should purge out of the filter and not re-accumulate ... if it is, then you must have a leak on the suction side of the pump. You see any air in the pump?

I do not know anything about your pool or the return/skimmer locations to offer any insight into your last question.

13. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Good to know jbizzle, I only see a slight pressure difference if anything also.

I do see air in the pool pump strainer. If I had a suction leak how am I still able to prime, this condition only exists when I am manually vacuuming with vacuum hose attached directly to skimmer no basket.

I just updated my pool signature thanks for the reminder.

I noticed you have the same size pool filter how many LBs of DE do you normally add. How often do you replace the DE? I usually replace after I have already backwashed and recharged once.

14. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

I just have a bucket that I fill up a certain amount with DE ... I weighed it originally, now I do not remember. Should be the recommended amount for a full recharge and only about 80% after just a backwash. I break the the filter down once a years or so.

While vacuuming, there is a lot more suction head loss, so could be that your hose is leaking or it is pulling hard enough to draw in air in a location where it does not under normal operation. I hope you are using a leaf canister and not relying on the pump basket to catch everything.

15. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Man I've been over servicing my filter took me about 3 hours yesterday to complete, gonna try doing it annually.

No I never thought about using a leaf canister. Which works best a leaf canister or skimmer vac plate?

16. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Never used a skimmer vac plate, although think I have read that they may not work very well. So, I would say the leaf canister is better ... and could be used with any suction cleaner.

Well, I only need to backwash 1-2 times per year, so I never get that much buildup. If you are having to backwash very often, then you might need to break it down more often.

17. ## Re: Programming Pentair 3HP Vairable Speed Pump need Help calculating flow rate

Circular water circulation usually works best. Sometimes it is obvious by looking at the layout of returns and skimmers. Sometimes it takes trial and error to see if debris gets moved toward the skimmers efficiently.

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