Why does my pump never finish priming?

[jfreeman]

I installed a Century VGreen 270 variable speed pump motor earlier this year in my Hayward Super II pump housing. Lately I've noticed that the pump never seems to achieve full prime. There is always a bubble that fills at least the dome of the lid, as can be seen in this video. What is causing this? My suspicion is that there might be leaves stuck in a skimmer line, but I don't know how to test that theory. I have watched this video a hundred times, but I don't find it convincing. (I just watched this video and it says the same thing.) I have played with the valves on the suction side, turning on and off the two skimmers and main drain, back and forth, different combinations, for ten minutes, and it never finished priming (though I did pull some leaves into the basket, which bolstered my theory). I don't understand how putting a bladder in the line at city water pressure will do more to unclog it than running the pump at max speed.

The default priming speed is 2600. I have cranked it up to 3200, and the pump has still not finished priming.

A related question that I may re-ask in another thread if I can't get an answer in this thread using this thread's title: I don't know what is a "safe" pressure for my filter, a Hayward Pro-Grid 60 sqft DE. The pressure spans a VERY wide range, from 7 PSI to 35 PSI depending on the pump speed. How can I determine what the "right" operating pressure is? I've read "backwash the filter, turn the pump on, and that's the baseline pressure". Does that mean backwash AND _refill the filter with DE_? Does that mean turn the pump on _to its maximum speed_? If I take a baseline pressure reading at top speed, but never run the pump again at top speed, then how is that baseline useful? If I take a baseline reading at my typical speed, then what does an increase in pressure tell me? If I can run the system at a much higher pressure by setting the pump to top speed, then what is the meaning of a pressure that is higher than a low speed baseline, but still low pressure?

 

[mas985]

I would be surprised if the pump could prime at 2600 RPM. High flow rates are necessary to push all of the air out of the pump. Have you tried full speed for priming?

A filter's pressure is dependent on pump motor RPM. Higher RPM results in higher flow rates which results in higher head loss and pressure is a direct measurement of head loss. A safe pressure is anything that is below the maximum rating for the filter. Other than that, there is no "normal". Every pool is different.

However, it is important to know what your filter's normal pressure is as a baseline. That is generally after cleaning and yes with DE recharged (normal operation). As for which speed to use for the reference, you can use your normal operating RPM or full speed or any other speed. Just be consistent. When the filter pressure rises by 25%, then you need to clean the filter again. Higher RPM is usually easier to see a change in pressure so you can use full speed as a reference but once a week you will need to run at full speed to be able to tell when you need to clean the filter. If you set priming speed to full speed, you can check the filter pressure when the pump first turns on and after stabilization. At lower speeds, it may be more difficult to tell when a filter cleaning is necessary. Also, there is nothing wrong with using multiple RPM as a reference so you have secondary checks.

But whatever you do, don't go by the filter gauge "red zone". That will be very inaccurate at lower RPM and is actually too excessive even at full speed.

Last point, if the pump is losing prime when it is off, then the pump lid, drain plugs or something else is leaking air into the system. A pump should never lose prime unless the pump lid is opened. Use pool lube on all the gaskets to make sure there is a tight seal.

 

[jfreeman]

I just went outside and ran the pump at max speed, 3450 RPM, for a few minutes. It never finished priming. I'm guessing there must be an air leak somewhere on the suction side? How can I find it? I had resealed the lid this morning with lube, and the lid gasket is young from replacement back in January.

When I first walked out there, I noticed water at the top of the filter, sitting on the cap. It might have been left over from when I opened the air relief valve this morning. But when I turned the pump to max speed, I noticed water streaming out of the cap and down the side of the filter, as can be seen next to the blue arrow in this picture:



Does my cap (technically called the air relief assembly) need to be replaced? Does my entire filter need to be replaced? The filter was manufactured in February 2009. I replaced the pressure gauge earlier this year, and cleaned and re-lubed the filter gaskets at the same time.

 

[Jimrahbe]

J,

Just because there is an air bubble under the pump lid, at low speed, does not mean the pump has not primed.

I don't know anything about the V-Green system.. Does it prime at a fast speed and them slow down to your run speed?

When running with the "bubble" what does the water coming out of your pool returns (eyeballs) feel like.. Do you have good strong flow?

My pump runs at about 1200 RPM and my filter pressure is less than 2 lbs. At that speed I have plenty of flow to turn on my SWCG and skim the pool. Even though I have a small bubble under the pump lid.

Just so that we are all on the same page... Why do you think your pump is not "finished" priming?

Thanks,

Jim R.

 

[mas985]

It could be just the air relief valve that is leaking. You can unscrew that and lube it with pool lube and while you are at it, lube the pump lid gasket and drain plug gaskets. See if that helps.

Also, at full speed, what was the filter pressure?

If there is a clog in the impeller, it might prevent the pump from priming. This can be indicated by low pressure at full speed.

 

[jfreeman]

I don't know anything about the V-Green system.. Does it prime at a fast speed and them slow down to your run speed?

It primes at mid-speed (default 2600 RPM, configurable, I left it there) and then moves into the scheduled speed. I have 2 hours of a faster speed in my schedule, which I think does a better job skimming, then 10 hours at a slower speed.

When running with the "bubble" what does the water coming out of your pool returns (eyeballs) feel like.. Do you have good strong flow?

How do I judge this? I can feel something, but not much at low speed. Low speed hardly even makes a visible stream at the skimmers.

My pump runs at about 1200 RPM and my filter pressure is less than 2 lbs. At that speed I have plenty of flow to turn on my SWCG and skim the pool. Even though I have a small bubble under the pump lid.

How do you measure your flow? Is your bubble as big as mine in this video? I don't know how big is your calibration of "small bubble".

Just so that we are all on the same page... Why do you think your pump is not "finished" priming?

Because of the bubble. If that is not definitive, as you say, then what is?

It could be just the air relief valve that is leaking. You can unscrew that and lube it with pool lube and while you are at it, lube the pump lid gasket and drain plug gaskets. See if that helps.

I did that earlier this year, and it didn't seem to help. Could the gaskets be deformed after 12 years and need replacement?

Also, at full speed, what was the filter pressure?

About 30 PSI.

If there is a clog in the impeller, it might prevent the pump from priming. This can be indicated by low pressure at full speed.

I'm guessing this is not the problem.

 

[mas985]

30 PSI could indicate a return side problem. Perhaps the filter is very dirty. When did you clean it last?

Also, what was the make/model of the pump that you put the VGreen on?

I did that earlier this year, and it didn't seem to help. Could the gaskets be deformed after 12 years and need replacement?

Yes. There is also an o-ring where the entire top of the filter is screwed on to the housing. That could be leaking as well.

 

[wireform]

I know of many DE filters that run with a single speed pump of all hp's. Non of them run at 30 and 35 psi. You may have a problem from the pressure side of the pump through the filter which is holding back flow which in turn won't let the suction side do its proper thing.

 

[jfreeman]

30 PSI could indicate a return side problem. Perhaps the filter is very dirty. When did you clean it last?

I cleaned it May 8 of this year. Opened it up, hosed down all the panels, reassembled, recharged.

Also, what was the make/model of the pump that you put the VGreen on?

Hayward Super II. Inyopools told me it was the right motor for that pump.

Yes. There is also an o-ring where the entire top of the filter is screwed on to the housing. That could be leaking as well.

Right, I'm familiar with all the gaskets from my experience cleaning it in May.

I know of many DE filters that run with a single speed pump of all hp's. Non of them run at 30 and 35 psi. You may have a problem from the pressure side of the pump through the filter which is holding back flow which in turn won't let the suction side do its proper thing.

What might that problem be? I'm getting the feeling I'll just have to hire a pro to come diagnose the problem in person.

 

[Jimrahbe]

J,

Does your DE filter have a Recirculate mode? If so, try that mode and see what happens. Recirculate by-passes the filter.

My bubble is about half the size of yours, but the bubble does get bigger as my filter gets dirtier.

Thanks,

Jim R.

 

[wireform]

I cleaned it May 8 of this year. Opened it up, hosed down all the panels, reassembled, recharged.

Hayward Super II. Inyopools told me it was the right motor for that pump.

Right, I'm familiar with all the gaskets from my experience cleaning it in May.


What might that problem be? I'm getting the feeling I'll just have to hire a pro to come diagnose the problem in person.

If no recirclate option open the filter, remove the grids and get rid of the DE by way of filter drain and garden hose. Close all up and see if anything changes. That'll tell you if the filter is causing the problem.

 

[jfreeman]

Does your DE filter have a Recirculate mode? If so, try that mode and see what happens. Recirculate by-passes the filter. My bubble is about half the size of yours, but the bubble does get bigger as my filter gets dirtier.

I put the filter in recirculate mode, ran the pump at max speed, and even closed the skimmer lines. The bubble didn't change at all. When the pump was off, the bubble did not appear to grow larger.

 

[mas985]

More than likely your filter needs cleaning. May 8th was quite a while ago for a 60 sq-ft DE filter. Most should be cleaned at least once per quarter and as I mentioned before, when the filter pressure rises by 25% from the clean pressure.

I put the filter in recirculate mode, ran the pump at max speed, and even closed the skimmer lines. The bubble didn't change at all. When the pump was off, the bubble did not appear to grow larger.

That could make this worse. All suction ports need to be opened.

Does the filter gauge go to 0 when the pump is off?

 

[jfreeman]

More than likely your filter needs cleaning. May 8th was quite a while ago for a 60 sq-ft DE filter. Most should be cleaned at least once per quarter and as I mentioned before, when the filter pressure rises by 25% from the clean pressure.

I've backwashed it several times in the interim. When I say "clean", I'm talking about a full disassembly. I was under the impression that backwashing needs to be done when pressure rises, but cleaning can wait much longer, e.g. once a year.

That could make this worse. All suction ports need to be opened.

Even when all suction ports are open, the bubble stays. I've tried all combinations of suction ports.

Does the filter gauge go to 0 when the pump is off?

Yes.

 

[mas985]

Ok, then when was the last time you backwashed? You might try that.

Also, double check all return side valves to make sure there are no restrictions for the return flow.

Can you post a picture of your pad equipment?

Do you have any check valves on the return side plumbing? Sometimes they will fail, especially the cheaper ones.

 

[jfreeman]

Ok, then when was the last time you backwashed? You might try that.

I last backwashed November 13. I'm planning to take apart the filter tomorrow to check the gaskets and filter panels and order replacements if necessary.

Also, double check all return side valves to make sure there are no restrictions for the return flow.

Right now I send all of the return to my spa.

Can you post a picture of your pad equipment?

I've attached them.

Do you have any check valves on the return side plumbing? Sometimes they will fail, especially the cheaper ones.

There are no check valves anywhere in my system.

 

[ajw22]

See what your filter pressure is if you set your return to your pool or to pool+spa. And see if your pump bubble changes.

Your spa return will have more restrictions then the pool return.

 

[mas985]

Besides running on pool mode, the device after the chlorinator looks like it is an Oretega check valve:

If you remove the top, you can check the internals for proper function. But that would only affect pool mode.

 

[jfreeman]

The air bubble completely disappears if I open the return to the pool. I guess that answers my original question. Now I'm left with new questions about how to balance suction, return, and pump speed to keep the pool acceptably clean at minimum cost, but I'll start a new thread for them.

 

[mknauss]

but I'll start a new thread for them.

Please keep your items in this thread.