Pentair pump - will only prime when I trick it - any time Variable speed drops below near max, it won't prime again

ionizer

Gold Supporter
Jun 7, 2016
214
Marlboro, NJ
Pentair Intelliflow 2 VST Pump - about 3 yrs old. Pool recently opened, pump was primed and running.
I noticed one day later my pump was not running and reason was it had not primed (if it can't prime after 11 minutes, it goes into an error state.)

So I did the following:
(1) Backwashed/rinsed, added DE since my pressure was +10 from the red line on the gauge
(2) emptied all baskets, etc.
(3) I bought a new o-ring for the pump cover and used magic lube to ensure a snug fit
(4) I loaded a bunch of water (home depot buckets and hose) into the pump before trying to prime

Simply put, the pump won't prime. It keeps funneling water, but not enough to create suction.

I close valves (waterfall is normally not on), close main drain, leaving only one skimmer and returns open, still won't prime. It just won't suction fast enough to do so and create the seal in the pump area.

So, I backwash one more time and it of course primes no problem in 15 seconds.

I then QUICKLY turn off the pump, switch from backwash to filter and then prime the pump again, WALLAH, it primes!!

But as soon as my VARIABLE pump hits the schedule to go down in speed (I don't want it running at full speed all the time of course) it is unable to prime.

Full speed = 3450RPM
Next drop down from noon to 4pm = 2450RPM
Usually from 6pm-7am I have it go at a trickle at like 1800RPM.

In the past, this has always been fine. Now suddenly it no longer is.

No: I am not seeing bubbles when primed, so I don't believe I have a leak?

What did I notice: I had a few plastic pieces spit out of my return in the deep end. It looks like maybe some pieces of the DE grid, but I am not sure.

What do I do? Do I contact mfg? Do I need someone to pressure test? I can't keep running the pump at max speed (defeats the point of the variable pump) and I can't keep manually backwashing and then tricking it to go back into priming.

Please help! Pool is otherwise balanced!!
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,628
Pleasanton, CA
A pump should not lose prime unless the pump lid is removed. If you turn the pump off, does the pump basket eventually empty? If so, you have an air leak.
 
Last edited:

ionizer

Gold Supporter
Jun 7, 2016
214
Marlboro, NJ
A pump should not lose prime unless the pump lid is removed. If you turn the pump off, does the pump basket eventually empty? If so, you have an air leak.
sorry, it appears my settings for email notifications were turned off.

this has been solved, but here is run-down:

(1) When I had the pool on recirculate (avoiding the filter) it primed fine...
(2) I opened my DE filter to discover every single one of my grid center portions were crushed. I am not sure what caused this to happen, pool was properly closed for the winter, so should not have been any water in it that would cause it to freeze. However, the grids were only 5 yrs old. All the grids were fine, except for the center portions which looked like they had all been smashed with a hammer.

so i did what i had never done before and replaced it. fitting the grid in was a huge PITA, but with wife's help, we eventually figured it out.

since then, primes w/o any issue and pool is sparkling clean

....so does anyone know what causes the middle of the grids to basically get all crapped up and have plastic pieces all inside them?
 

ionizer

Gold Supporter
Jun 7, 2016
214
Marlboro, NJ
I do run the pump at full speed (3450rpm) from 7am-11am, then i go down to like 2000rpm from 11am-6pm and then 6pm-6:59am i run at like the lowest setting which still has water trickling through

is that an issue?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,628
Pleasanton, CA
There is no need to run a pump at full speed unless you running spa jets or a large waterfall. It is just waste of energy plus it may possibly damage the filter.

You should run mostly at one speed. The lowest speed which the skimmers still function. This is where the water travels over the top of the weir door.

There is really no need to run at lower or higher speeds than the what the skimmer needs. Unless you are running solar or a heater.
 

ionizer

Gold Supporter
Jun 7, 2016
214
Marlboro, NJ
There is no need to run a pump at full speed unless you running spa jets or a large waterfall. It is just waste of energy plus it may possibly damage the filter.

You should run mostly at one speed. The lowest speed which the skimmers still function. This is where the water travels over the top of the weir door.

There is really no need to run at lower or higher speeds than the what the skimmer needs. Unless you are running solar or a heater.
i do have 3 waterfalls, and yes when running them it does kind of need to be at max

i thought running at full speed was a good idea because i figured it would circulate the water more, thus filtering it more

what's the point of a variable speed then if i should only run at one speed?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,628
Pleasanton, CA
what's the point of a variable speed then if i should only run at one speed?
To save energy. Unlike a single speed or a two speed, a VS is more flexible and allows you to choose the most energy efficient speed for each task. If there is only one task, such as circulation, then only one speed is necessary and it is usually a low speed. If you have more than one task, you may need more than one speed. However, running the waterfalls should not be an everyday task and only when using the pool. Running a waterfall everyday could have a negative effect on PH.

If you need to run on full speed while using the waterfalls and it is damaging the filter, you may need a filter bypass. Your filter is a 48 sq-ft filter and has a max flow rating of 96 GPM which might be exceeded at full speed.

i thought running at full speed was a good idea because i figured it would circulate the water more, thus filtering it more
Not necessary. Most filters do not do well at high flow rates. Debris is forced through the filter. At lower speed, the filter does a much better job of filtering and saves energy. Most people on the forum with VS pumps hardly ever run at full speed or even half speed. There is just no benefit to running water through a filter at high speed.
 

kadavis

TFP Guide
In The Industry
Apr 5, 2015
1,628
tucson, arizona
If your running the pump at full speed (which I don't suggest) an it is primed and then switches to a lower speed the pump is still primed. But if you get a priming error there may be something wrong with the drive, you can go into the menu and disable the priming feature and see if that works. This is only a temporary fix and you may have to contact Pentair support
 

ionizer

Gold Supporter
Jun 7, 2016
214
Marlboro, NJ
To save energy. Unlike a single speed or a two speed, a VS is more flexible and allows you to choose the most energy efficient speed for each task. If there is only one task, such as circulation, then only one speed is necessary and it is usually a low speed. If you have more than one task, you may need more than one speed. However, running the waterfalls should not be an everyday task and only when using the pool. Running a waterfall everyday could have a negative effect on PH.

If you need to run on full speed while using the waterfalls and it is damaging the filter, you may need a filter bypass. Your filter is a 48 sq-ft filter and has a max flow rating of 96 GPM which might be exceeded at full speed.

Not necessary. Most filters do not do well at high flow rates. Debris is forced through the filter. At lower speed, the filter does a much better job of filtering and saves energy. Most people on the forum with VS pumps hardly ever run at full speed or even half speed. There is just no benefit to running water through a filter at high speed.
not sure why i never got notification of these via email... seems like my activation of previous threads isnt actually resetting.

anyway, thank you for the information. I never thought about skipping the filter when running the waterfalls, but that is a much more sensible thing to do

i hope i didnt re-damage my filter grids by running at 3450 rpm in order to run the waterfalls, but from now on, im going to use the bypass mode when using them, thanks so much
 

ionizer

Gold Supporter
Jun 7, 2016
214
Marlboro, NJ
If your running the pump at full speed (which I don't suggest) an it is primed and then switches to a lower speed the pump is still primed. But if you get a priming error there may be something wrong with the drive, you can go into the menu and disable the priming feature and see if that works. This is only a temporary fix and you may have to contact Pentair support
thanks, it ended up being that my entire filter grids had basically condensed into itself (the circular portion where the water flows) this was obviously restricting water flow, causing the issue apparently

replaced all the grids and was back to normal

now i know not to run my pump at high speeds unless i am bypassing the filter