Air In Pump Basket Increases As Filter Gets Dirty.

[lrodptl]

Last fall I changed all my plumbing from 1.5" black flex to 2" PVC. There are no leaks and there is no air visible in the pump basket til the filter gets dirty then there's a lot of air. The pump is the original 56gpm 1 HP Superpump. Does this sound like the pump needs to be upgraded now? The old plumbing had one return line that teed off at the first return port and continued to the far return port. I now have it teed right after the pump and 2 separate 2" lines to each return. The suction lines are now also separate 2" lines. Thanks

[Pool-newb]

I have a similar situation and I've learned to just live with it.

On my system I believe that the water is cavitating because there are some bends and turns a bit too close to the intake side of the pump. However, I have a two speed pump and when running on high speed, no water collects in the pump basket because it is all passed through to the sand filter. On low speed it takes a day or two but eventually the pump basket fills with air.

And like you, I notice a big difference in how much air comes in if the filter is clean or dirty. There is also more air if the pump basket gets leaves in it, or if the skimmer or drain gets a little plugged with leaves or debris.

I'I have 2" above ground and 1.5" below ground.

[lrodptl]

I have a similar situation and I've learned to just live with it.

On my system I believe that the water is cavitating because there are some bends and turns a bit too close to the intake side of the pump. However, I have a two speed pump and when running on high speed, no water collects in the pump basket because it is all passed through to the sand filter. On low speed it takes a day or two but eventually the pump basket fills with air.

And like you, I notice a big difference in how much air comes in if the filter is clean or dirty. There is also more air if the pump basket gets leaves in it, or if the skimmer or drain gets a little plugged with leaves or debris.

I'I have 2" above ground and 1.5" below ground.

I think my pump is either now undersized or worn out. Anybody else agree?

[Pool Clown]

The velocity or "speed" of the water moving through the pump is what helps pass the air . As the filter gets dirty, the velocity falls and there is no longer that condition where the air passes easily. I doubt anything is wrong with the pump (as long as it isn't making any noise or leaking), but I would look at the filter if the pressure rises quickly after cleaning.

[lrodptl]

The velocity or "speed" of the water moving through the pump is what helps pass the air . As the filter gets dirty, the velocity falls and there is no longer that condition where the air passes easily. I doubt anything is wrong with the pump (as long as it isn't making any noise or leaking), but I would look at the filter if the pressure rises quickly after cleaning.

I'm baffled. I've disassembled the DE filter twice and I see no tears or obstructions. It was green with dead algae. After cleaning,the pressure starts at 12 PSI with no air bubbles at all in the basket. When it reaches 20-22 PSI there is a lot of air visible. Last night I shut it off at 20 PSI and this morning it started at 15 PSI with almost no air in the basket and no backwashing or cleaning performed. I can't explain that. After shut down and start up the basket is empty of water and the pump primes itself,I thought the water should remain full in the basket. One of the return ports is coughing a bit but there is no water loss at all.

[Pool Clown]

I'm baffled. I've disassembled the DE filter twice and I see no tears or obstructions. It was green with dead algae. After cleaning,the pressure starts at 12 PSI with no air bubbles at all in the basket. When it reaches 20-22 PSI there is a lot of air visible. Last night I shut it off at 20 PSI and this morning it started at 15 PSI with almost no air in the basket and no backwashing or cleaning performed. I can't explain that. After shut down and start up the basket is empty of water and the pump primes itself,I thought the water should remain full in the basket. One of the return ports is coughing a bit but there is no water loss at all.

Two things

1. Could you be putting too much D.E. in? What size is the filter, and how much do you put in?

2. When you shut off the pump, watch the pump cover and see if you get any air bubbles coming up to the top of the lid. I may take a min or two. Trick: If you see bubbles but need a better view, take the pump basket out and re prime the pump, then shut down and observe for air. It will either come from the pump inlet, the pump lid o ring, or from the bottom of the pot. In that case see if you have a threaded plug in the pump down near the bottom of the pot. That plug may have an o ring that has gone bad. This is a common problem with Sta-Rite pumps.

[lrodptl]

I'm baffled. I've disassembled the DE filter twice and I see no tears or obstructions. It was green with dead algae. After cleaning,the pressure starts at 12 PSI with no air bubbles at all in the basket. When it reaches 20-22 PSI there is a lot of air visible. Last night I shut it off at 20 PSI and this morning it started at 15 PSI with almost no air in the basket and no backwashing or cleaning performed. I can't explain that. After shut down and start up the basket is empty of water and the pump primes itself,I thought the water should remain full in the basket. One of the return ports is coughing a bit but there is no water loss at all.

Two things

1. Could you be putting too much D.E. in? What size is the filter, and how much do you put in?

2. When you shut off the pump, watch the pump cover and see if you get any air bubbles coming up to the top of the lid. I may take a min or two. Trick: If you see bubbles but need a better view, take the pump basket out and re prime the pump, then shut down and observe for air. It will either come from the pump inlet, the pump lid o ring, or from the bottom of the pot. In that case see if you have a threaded plug in the pump down near the bottom of the pot. That plug may have an o ring that has gone bad. This is a common problem with Sta-Rite pumps.

I actually put less than the required DE in. I have a 20 year old Hayward Super Pump. I'll do what you suggested. Thanks for reading.

[Pool Clown]

If your running less than required DE, You may need the have the grids themselves cleaned chemically.

The fabric grids in a DE filter are merely a platform for the DE, (the real filter in this case) and they are not meant to be used as the filter. Putting in less than what you are supposed to, leaves the grid open to get impregnated over time with dirt,oils, etc. They will not always clean off with a hose or a backwash.

Since you have taken the filter apart and you have seen the grids, I'll guess and say you don't have any grids that have broken/ collapsed, That could've been another cause of your problem.

[Bugman1400]

I've got one more possibility relating to the pump. My theory involves the impeller and the shaft seal to the motor. It quite possible that air is being sucked in through the seal around the motor shaft. If the the pump is off, it is possible that the seal completely seals the shaft and prevents no leakage. However, when the motor spins and is slightly off center or lobed then you might get a cam effect that would keep the seal slightly open for air to be sucked in from the impeller. Remember, the motor spins at ~3500 RPM.

[lrodptl]

I've got one more possibility relating to the pump. My theory involves the impeller and the shaft seal to the motor. It quite possible that air is being sucked in through the seal around the motor shaft. If the the pump is off, it is possible that the seal completely seals the shaft and prevents no leakage. However, when the motor spins and is slightly off center or lobed then you might get a cam effect that would keep the seal slightly open for air to be sucked in from the impeller. Remember, the motor spins at ~3500 RPM.

With the pump off,should water remain in the basket without any fall off? My basket is empty in the morning after 12 hours off.

[Pool Clown]

I've got one more possibility relating to the pump. My theory involves the impeller and the shaft seal to the motor. It quite possible that air is being sucked in through the seal around the motor shaft. If the the pump is off, it is possible that the seal completely seals the shaft and prevents no leakage. However, when the motor spins and is slightly off center or lobed then you might get a cam effect that would keep the seal slightly open for air to be sucked in from the impeller. Remember, the motor spins at ~3500 RPM.

Any air drawn in by the seal would not be seen in the pot.

Seal is also constantly under pressure from a spring, forcing the two halfs of the seal together, whether pump is on or not.

If the shaft was lopsided enough to make the seal leak...

#1 The pump would tear itself apart. 3450 rpm's you know.

#2 You're neighbor would come over wondering why pump pieces were landing in his pool.

#3 how does a motor shaft all of a sudden get bent that much?

When seals leak, it's usually water. I did once have a seal draw air in, Even though the seal is in the pressure side of the pump. But that air would wind up in the filter.

[lrodptl]

I've got one more possibility relating to the pump. My theory involves the impeller and the shaft seal to the motor. It quite possible that air is being sucked in through the seal around the motor shaft. If the the pump is off, it is possible that the seal completely seals the shaft and prevents no leakage. However, when the motor spins and is slightly off center or lobed then you might get a cam effect that would keep the seal slightly open for air to be sucked in from the impeller. Remember, the motor spins at ~3500 RPM.

Any air drawn in by the seal would not be seen in the pot.

Seal is also constantly under pressure from a spring, forcing the two halfs of the seal together, whether pump is on or not.

If the shaft was lopsided enough to make the seal leak...

#1 The pump would tear itself apart. 3450 rpm's you know.

#2 You're neighbor would come over wondering why pump pieces were landing in his pool.

#3 how does a motor shaft all of a sudden get bent that much?

When seals leak, it's usually water. I did once have a seal draw air in, Even though the seal is in the pressure side of the pump. But that air would wind up in the filter.

I have found 2 suspicious issues. I have 2 quick disconnect ball valves teed off for each suction port. It appears neither valve face is flush with the union when tightened down. The T appears to be twisted coming out of the ground and I'll have to dig down to see if I can get enough play to get these valves seated flush. Think I could be sucking air through here? I tried the water test but saw nothing.

[Pool Clown]

I have found 2 suspicious issues. I have 2 quick disconnect ball valves teed off for each suction port. It appears neither valve face is flush with the union when tightened down. The T appears to be twisted coming out of the ground and I'll have to dig down to see if I can get enough play to get these valves seated flush. Think I could be sucking air through here? I tried the water test but saw nothing.

What your describing would draw more air when the filter press is low than when the pressure is high. The union would leak more when the water is moving freely. As the pressure builds, water flow slows down. The draw on the suction line goes down. Therefore would not pull as much air than when system was running at a lower pressure. In other words, you would get the opposite symptom than what you have.

Does that make sense?

[lrodptl]

I have found 2 suspicious issues. I have 2 quick disconnect ball valves teed off for each suction port. It appears neither valve face is flush with the union when tightened down. The T appears to be twisted coming out of the ground and I'll have to dig down to see if I can get enough play to get these valves seated flush. Think I could be sucking air through here? I tried the water test but saw nothing.

What your describing would draw more air when the filter press is low than when the pressure is high. The union would leak more when the water is moving freely. As the pressure builds, water flow slows down. The draw on the suction line goes down. Therefore would not pull as much air than when system was running at a lower pressure. In other words, you would get the opposite symptom than what you have.

Does that make sense?

Yes,one valve is definitely leaking right now. If what you're saying is true,then I'm truly baffled.

[Bugman1400]

I've got one more possibility relating to the pump. My theory involves the impeller and the shaft seal to the motor. It quite possible that air is being sucked in through the seal around the motor shaft. If the the pump is off, it is possible that the seal completely seals the shaft and prevents no leakage. However, when the motor spins and is slightly off center or lobed then you might get a cam effect that would keep the seal slightly open for air to be sucked in from the impeller. Remember, the motor spins at ~3500 RPM.

Any air drawn in by the seal would not be seen in the pot.

Seal is also constantly under pressure from a spring, forcing the two halfs of the seal together, whether pump is on or not.

If the shaft was lopsided enough to make the seal leak...

#1 The pump would tear itself apart. 3450 rpm's you know.

#2 You're neighbor would come over wondering why pump pieces were landing in his pool.

#3 how does a motor shaft all of a sudden get bent that much?

When seals leak, it's usually water. I did once have a seal draw air in, Even though the seal is in the pressure side of the pump. But that air would wind up in the filter.

I think you're right. If the seal did leak, the air would end up in the filter and not in the pot. I have seen shafts that were lobed from dirt or baked-on crud or rust/corrosion. I've also seen bearings that go bad and cause the shaft to wobble. However, this is usually associated with a terrible noise.

I think its the ball valves on the suction side. I have a 3-way on my suction and I also get air in the pot after a few minutes with the pump off......I thought that was normal. The reason I know my 3-way leaks is because it spits out water when I accidently switch from one line to the other without shutting the pump off.

[Pool Clown]

If you have a multi port valve, put it recirculate and let it run like that and ill bet the pump will stay full (I still think its somewhere down stream of the pump). If you have a push pull backwash valve, thats a little more involved. You have to take the filter lid off (again), and take the filter bundle out of the tank. Clean the tank real good cuz everything is going to go into the pool. Put the tank lid back on (no grids) and start back up and see. Actually, this test is a bit better in that, it can be nothing other than the grids if the pump is ok now.

[elceser]

You are sucking air on the inlet. I just had this issue. The piece of pipe threaded into the inlet of the basket strainer was not tight. I didn't find it until I closed the deep drain and skimmer suction valves. I closed the filter multiport valve and pressurized (SLIGHTLY....DON'T BURST ANYTHING!!!!) the pump, strainer and pipe with a garden hose to find the leak. I loosened a union in the strainer suction and tightened the strainer inlet fitting. All is now free of air infiltration. If not this fitting, some other is not tight/sealed. I use tefon tape. My installers used silicone caulk.

I originally thought that the line from the skimmer to the basket strainer was clogged with debris.

Use a silicone (stopcock) grease on the strainer lid o-ring.

Note: As the filter clogs and the pressure goes up, the differential pressure across the pump (delta P) increases (it is sucking harder).

[Pool Clown]

Note: As the filter clogs and the pressure goes up, the differential pressure across the pump (delta P) increases (it is sucking harder).

When head on the pump increases, Vacuum (Hg) decreases. Lets say for a moment, the filter is a 2 way valve. When you start to close the valve (filter getting dirty), the pumps ability to draw the same amount of water decreases (no place for the water to go). You will get a differential, but most of the gain is on the pressure or outlet side of the pump.

[lrodptl]

Note: As the filter clogs and the pressure goes up, the differential pressure across the pump (delta P) increases (it is sucking harder).

When head on the pump increases, Vacuum (Hg) decreases. Lets say for a moment, the filter is a 2 way valve. When you start to close the valve (filter getting dirty), the pumps ability to draw the same amount of water decreases (no place for the water to go). You will get a differential, but most of the gain is on the pressure or outlet side of the pump.

I found the pump basket sucking air beneath one of the knobs which was cracked,this took care of most of the issue. Still sucking a little air at one of the ball valves but everything is much better. Thanks. None of my fittings are tefloned or caulked.

[Pool Clown]

None of my fittings are tefloned or caulked.

Fix that and i think you will be good to go.

[lrodptl]

None of my fittings are tefloned or caulked.

Fix that and i think you will be good to go.

Appreciate all the help.

[texaspool]

I have a similar question, what if the pump runs completely dry after 12-24hrs of operation? The pressure gauge on the sand filter will show about 30psi but no water is flowing at all. I can turn the pump off, turn the multiport valve to backwash, the pump will prime itself and backwash normally, then when I put the vavle back to filter everything works fine and the pressure goes back down to normal. About 12hrs later, the pump once again has no water in it and is running dry with a psi showing around 30!

[billp]

There are no leaks and there is no air visible in the pump basket til the filter gets dirty then there's a lot of air.

When flow is high, air is pulled out of the pump pot. As flow decreases, a bubble is more likely to remain. In some low flow systems there is always air in the pot. This drives people crazy. It is not a problem in your case. Not cavitating, just low flow.