Poll for Users of Variable Speed Pumps - Please Read

[phalcon51]

Since installing my EcoStar VSP a month ago I've been having a problem with air collecting in the strainer basket. If I let it go for 2 or 3 days it will drop all the way into the inlet port, so I end up running a high speed cycle, about 3200 rpm for 5 min. or so, to purge the air out on a daily basis. I started a thread about it here and received a reply from Mark (mas985) postulating that it might be a result of dissolved oxygen and nitrogen in the water out-gassing from the reduced pressure on the suction side of the pump. Chemgeek disagrees with that idea, so the debate goes on. I'm curious as to how many other VSP owners are experiencing the same problem. I'd appreciate it if you would answer the poll and follow up with a post stating what brand and model pump you have, what speed you run it at for most of the day and the approximate distance from your skimmer to your equipment pad.

Also, if you've contacted the pump manufacturer or the installer about the problem I'd be interested in hearing what they said about it.

I'm running my pump at 1500 rpm for 1 hour, then 2200 rpm for 2 hours and then back to 1500 rpm for the next 9 hours. I've got approximately 44' of 2" pipe from my skimmer to my pump.

Thanks for your input.

Gary

 

[chem geek]

Chemgeek disagrees with that idea, so the debate goes on.

I was wrong and corrected my post and added to that thread.

I have an IntelliFlo VF with a roughly 70' 1.5" pipe from the skimmer and a separate one from the two floor drains to the suction side of the pump. My non-solar filtration mode is around 1500 RPM with 26 GPM and around 275 Watts. I get some air bubbles/pocket at the top of the pump basket, but that's about it. Not what you are seeing. Most days also have solar running at least part of the day at around 3000 RPM with 48 GPM and around 1500 Watts. So I don't usually have full days at low speed every day.

However, even if you have your air pocket reach your inlet port, why is that a problem? Unless there is a large amount of air constantly getting into the pump, the air in the skimmer basket shouldn't really matter, should it? I suppose it cuts down the surface area for catching materials in the basket itself.

 

[mas985]

I would low speed of a two speed pump as well. I get a small air pocket when running on low speed for a fairly long time.

 

[Just-a-PB]

It should be a sealed system, so you shouldn't have air in the basket.
When you first start it up, can you purge air from the filter. If so you have some small seal leak somewhere.
I don't know anything about the Hayward VS pump, but the Intelliflo has a priming speed, so it will come on faster for a minute or so (depending on setting) and then ramp down to desired speed.

 

[chem geek]

Just-a-PB,

It is a sealed system, but the water itself contains dissolved gasses and the lower pressure on the suction side can have those gasses come out of solution to form bubbles. The question is more about what causes them to accumulate to such a great degree in the pump basket at lower speeds and I suspect this has to do with the lack of turbulence in the basket from the water flow compared to other pump basket designs for other pumps. Normally, it seems, that any air in the pump basket (as occurs when first priming a pump, for example) gets removed by the churning of the water in the basket "peeling off" bits of air as small bubbles, though that's just speculation on my part.

Richard

 

[Just-a-PB]

My equipment set is about 3' below my pool, so maybe this is why I dont get them.
But with they way you are describing it, I should.
Mystery!

 

[phalcon51]

chem geek - in my case I'm concerned about an actual air leak because of the amount of air that shows up each day. If I go on vacation for a week or two I don't want to worry about the pump losing prime and burning up seals and the pool turning into a swamp.

just a PB - I purge it daily by running the pump at 3200 rpm for 5 minutes, but I have the pump speed limited to 2200 rpm in the menu so I hsve to over-ride it to do that. I want to keep it limited because when you press the Quick Clean button for vacuuming the pump runs at the max allowed speed and 3200rpm is too high.

 

[susa]

I would have picked, Some small bubbles are visible.

would not be able to pick any option from the poll as the VF automatically senses changes in the flow and reprimes itself if needed. if I run ultraslow speeds at below 900 rpm, then, yes, the basket will slowly develop a bubble and it eventually grows larger but the basket never goes totally empty even then - have tested with 7 days at 850 rpm/90 watts 24 hours a day

for normal filter run, speeds at 20 GPM for 5 hours and 15 GPM for another 5 daily, there are a few visible bubbles, otherwise the VF automation handles it.

 

[mas985]

My equipment set is about 3' below my pool, so maybe this is why I dont get them.
But with they way you are describing it, I should.
Mystery!

At 3' below the water line, the pressure in the basket would be 1.3 PSI higher than a pump at the same level as the water line. On low speed, one might expect around 1" hg or -0.5 PSI so when the pump is below the water line, the pressure could be around +0.8 PSI. So it is not surprising that you do not see bubbles.

I ran a quick experiment where I heated some pool water in a pan until I saw the outgassing bubbles appear. The temperature went from about 20c to 38c or about a 6% rise in absolute temperature. This would equate to a 6% drop in absolute pressure or going from 14.7 psia to 13.8 psia or a suction measurement of 1.8" hg. So I think it is definitely a possibility that outgassing air can accumulate in a pump basket.

 

[Vandergraff]

I get some air bubbles/pocket at the top of the pump basket, but that's about it.

Likewise small air bubbles/pocket at top of the basket. I have mine currently set for 1500RPM for non-solar (per other threads I am still searching for the right RPM for my solar). However I don't have solar switched on at present (NCAL isn't yet in consistent solar heating weather) - so it is 1500RPM for 5.5 hours (with 30 minutes at 1700 RPM in the middle while the cleaner booster pump runs). Piping is 1.5"

The (small) bubbles seem to be pretty consistent from day to day.

Edit - I should add if take the 'lid' of to clean the basket air gets in and I have run the pump at a fairly high speed to purge the air afterwards

 

[teapot]

How about the possibility of cavitation, that would liberate bubbles out of solution and they will collect at any points close by when the speed changes from high to low. The high rpm may not be as efficient with the impeller but goes un noticed in normal flow but when that flow reduces the bubbles can surface on any part and you see them on the only clear bit the pump pre filter lid.

How about fitting a non return valve if you are worried about losing prime?

 

[chem geek]

Take a look at a photo of the Hayward Ecostar VSP and compare it to the Pentair IntelliFlo VF pump. Note the placement of the suction inlet into the pump which is very high up near the top of the pump basket in the case of the IntelliFlo while with the Ecostar it is just above the middle. I know in the IntelliFlo the outlet from the pump basket into the pump is at the bottom and I presume something similar for the EcoStar (hopefully).

When my pump runs with air in the basket after, say, cleaning the basket contents, then if it doesn't have too much air then the pump won't go into priming mode and instead just runs normally. So there is air near the top, but it slowly drops in amount even at the lower speed though stops reducing in size at some point. There is significant turbulence from the water flow even at low speed so the bottom part of the air pocket gets broken off and churned and partly going to the pump. So there is a balance of air buildup from whatever source (such as lower pressure causing dissolved air to form bubbles) vs. the air being removed by water flow through the basket. Faster speeds/flows result in more turbulence and smaller remaining air pocket; slower speeds/flows have less turbulence and a larger air pocket.

In my filter, though there is a bleed valve at the top with the pressure gauge, there is also a pressure equalization line that can remove any air buildup from the top of the filter which is outside the cartridge area (i.e. the unfiltered water quickly pushes air through a thin tube). If there is no air, then a small amount of unfiltered water bypasses the cartridges though this bypass does have a mesh screen on it so nothing big gets through. So getting small amounts of air in the system is not unusual and there are mechanisms for removing it.

It seems to me that the Esostar pump basket and inlet/outlet design may not work well at low flow rates compared to the IntelliFlo, but this is just one data point and we'll have to see what others with the Ecostar pump find with their systems running at low flow rates.

 

[mas985]

How about the possibility of cavitation, that would liberate bubbles out of solution and they will collect at any points close by when the speed changes from high to low. The high rpm may not be as efficient with the impeller but goes un noticed in normal flow but when that flow reduces the bubbles can surface on any part and you see them on the only clear bit the pump pre filter lid.

How about fitting a non return valve if you are worried about losing prime?

Cavitation bubbles can only exist at extreme vacuum (>28" hg) so once they migrate from the inlet part of the impeller to the outer diameter, the pressure rises and they collapse which is what causes the damage to the impeller. So you will never see cavitation bubbles unless you had a camera in the impeller inlet.

 

[teapot]

Thanks for that explanation Mas985,

I wondered as some of these big pumps are only being fed with 1 1/2" pipe if that was sufficient to cause enough of a pressure drop to cause cavitation at high flow rates.

My .75 hp is fed with 2 1/2" and runs with a constanly full pre filter basket but I do have one customer, who after an insurance claim went and bought a much bigger pump than needed (single speed) (because they could duh) and their pre filter usually has some air at the top but doesn't loose prime and is fed with 1 1/2" pipe.

 

[mas985]

With a large pump on small plumbing, the suction in the pump basket will be quite high on full speed so air in the pump basket is more likely due to the pump drawing in air from the pump lid and/or drain plugs. A single speed pump or a two speed on high should have enough flow rate to purge any outgassing that may occur since it is a small amount but if the pump is drawing in air from other places, then it may not be able to keep up with that.

With low speed on a two speed or VS pump, the suction is not very high but neither is flow rate so outgassing will still occur but there is not enough flow rate to push the small bubbles out of the pump like full speed.

 

[Ggrif]

Hmmmm, last post almost a year ago. Oh well, my particulars. I installed a Pentair Intelliflow this past January. It services an elevated random shaped gunite spa that waterfalls into a random shaped gunite splash pool. Total capacity maybe 5000 gallons. Pipe run from the skimmer to the pump is 31 feet, 2" line. If I run the pump at anything less the 1200 rpm it loses prime, strainer is virtually empty. Even at 1200 the strainer is 1/2 full at best. Air also collects in the filter, I manually bleed it off every other day if I think of it.

 

[mas985]

That sounds more like a leak. Try using pool lube on the pump lid seal.

 

[CraigMW]

I just replaced a WhisperFlo with an IntelliFlo and did a bunch of replumbing and line cleaning. Even with our MX8 cleaner that sometimes surfaces and sucks in air, I'm not seeing any air in the pump basket. The pump runs at about 2500 RMP for cleaning duties for 1hr and then kicks down to about 1500 RMP for circulation. There does seem to be some air in the filter from time to time, but not too much. The basket in the pump seems to be devoid of any air, esp. when running at low speed. We were having lots of cavitation issues until I determined that our cleaner line was clogged with a bunch of leaves. I replumbed a counterflow cleaner line circuit using an accessory pump that services the waterfall, and after cleaning out the cleaner line and adding a leaf catcher, it has been running great. Do you only get bubbles/cavitation at low pump RPM?

 

[jhalpinjr]

I have never been able to get my Ecostar to run full. After a few hours on low a bubble will form. From that point onward, it progressively gets lower.

I have had Hayward, and my PB onsite. I have been told this is "normal" on a VS pump.

But I ocntinue to hear other answers and opinions.

My vid from last year

 

[jongig]

I have a hard time seeing off-gassing being the cause of your problem and if this is normal I’d probably say prove it. If you want to see if off-gassing is even possible just get a glass jug, fill it with your pool water and then connect a vacuum to it and watch to see if bubbles show up in the water. If the vacuum is causing this you’ll see the bubbles.
Pressure test your pipes to see if there is a problem.