Sand Filter Getting Air

[godstreasures1]

I have a 24x52 above ground pool. I have just started to run the filter for the new season. I noticed today that after a short while my water flow coming from the jet is not as strong. I can hear air bubbling in the top of my sand filter. I took this apart to see if I could tell what was going on but no luck. I have checked all the pipes for leakes and no luck. Please advise.

[hrsdennis]

The most common place for an air leak is the lid to the hair and lint pot. Have you checked that? Also remember a leak on the suction side will suck air with the filter running and usually leak water when the filter is off.

Best of luck, Dennis

[godstreasures1]

I have checked all of that and made sure the o-rings were lubed with magic lube. I am stumped. It runs fine until enough air gets in then the pressure of the water goes down. I took the handle off my multiport valve and the gasket underneath is hard as a rock. Is it suppose to be? I was not sure but I greased it also.

[hrsdennis]

It's good to grease the spider gasket, but that should not be the problem. Sucking air occurs somwhere before the pump. Once the water leaves the pump it is being pushed under pressure and sprayes through any openings or breaks. Low water or an obstruction in the skimmer could cause the problem. Sometimes the flapper sticks and causes a wirlpool affect. If a cleaner is hooked up a leak in the hose could be the problem. With any of the possible causes you should see air in the hair and lint basket.

When you shut the unit off and let sit a few minutes then restart, does the pressure pick back up?

[godstreasures1]

The pressure stays at 20 while the pump is running. I can not find anything wrong with the suction side as far as leaks go. I have got hard pipe and I made sure everything was sealed tight. Any more suggestions?

[godstreasures1]

I keep the water at the third screw on my skimmer, it only has four screws. Is this far enough up? I can see a few air bubbles in the hair basket but not sure where they are coming from.

[hrsdennis]

Your water level is perfect. A few bubbles in lint basket is normal. They usually get sucked in through the lid. More grease might help that, just depends on the lid. Some of the older Hayward baskets warp and never seal 100%.

Unless you see the basket half full of air and making gurgling noises I don't think air is the problem.

Have you tried running the filter in circulate mode {if you have one}? This will let you know if the pressure problem is in the sand tank.

It is starting to sound like the water is not flowing through the sand properly.

[godstreasures1]

I have By Pass To Pool is this the same thing? What would I be looking for when I do this?

[hrsdennis]

You would be looking for a strong consistent flow of water back into the pool.

[godstreasures1]

If the flow decreases what would this mean?

[matt4x4]

Air getting in the filter can only mean one thing - leak on suction side of pump, air leak anywhere else and it'll be water getting pushed out the leak.
if it's not the strainer basket or low water level, have you chacked all connections between the skimmer and the pump - this is the ONLY place you could be drawing air from.
in answer to your recirculate question - nothing should change since you are effectively bypassing the filter and just pumping water from the pool through the pump and valve of filter (valve only) back into the pool.
Have you got a bypass chlorinator on the system - these usually connect into teh main lines before the pump and after the filter, the air could be getting in before the pump - check the stainless clamp to see if it's tight enough.

[godstreasures1]

I do not have a chlorinator but I will put the pool on bypass and run it. I will watch the pressure gauge and for leaks and post what I find. Thanks.

[godstreasures1]

I just put it on by pass to pool. The pressure went down to 8 and the flow of water coming from in front of the jet was the strongest I have ever felt. I didn't see any leaks though. What does this mean?

[hrsdennis]

Very good, it means we are eliminating some things.

Air leak not a problem. Pump is in good shape. Skimmer and lint baskets are clean.

The sand is apparently restricting the flow of water. I would try a good long backflushing and if that does not help try changing the sand.

Any other ideas?

[godstreasures1]

I just replaced the sand last year but had a problem with an older pump. I had to backflush alot could I have channeled the sand?

[KurtV]

I looked back through this thread a couple of times and don't see that anyone has talked about backwashing at all. Have you done that? You mentioned that the filter pressure is about 20 PSI, is that normal for your system?

[matt4x4]

If you channeled the sand you'd have a low backpressure and bad filtering but not air.
Since you had no leaks testing, you could still have a small suction side leak before the pump - it could be really small and would only ever draw air when the system is on, it may never draw a huge amount of air due to it's size.
If you turn the pump off, and let it sit overnight, you may find a small wet spot somewhere between the skimmer and the pump - you would have to trace that back to the leak uphill of it.
The only way water will come out of a suction side leak is with the system shut off.

[godstreasures1]

I have pvc piped my pool last year to prevent leaks. I have went over every joint with pvc glue to make sure I didn't miss something. I do have a piece of heavy blue hose from the pump to the filter. I made sure that I used pipe threading compound on all to prevent leaks. When I backwash my pressure runs 20 psi. This is the usual pressure for my pool on filter also.

[hrsdennis]

A freshly backflushed filter should pump about the same amount of water as the by-pass mode. It sounds like you are no where close to this.

Do you remember what type of filter media you used last year? I'm still thinking that is your problem.

[godstreasures1]

#20 silica sand from the pool store. How long are you suppose to backwash for. I usually backwash until I can't see any particles flying out the backwash pipe.

[hrsdennis]

#20 silica is fine. A rule of thumb for backflushing is about two minutes or untill the water come out clear.

After you backflush does the filter start out at 20lbs or does it start closer to 10 and then climbs quickly? If so how quickly?

[godstreasures1]

It usually starts out at about 14 and climbs over the next hour or two.

[hrsdennis]

It sounds like the filter is getting clogged with dirt or algea. You may just need to backflush every few hours until the water gets cleaned up. If you are filtering clean water I think we are back to changing the sand.

That's about it for my ideas, best of luck, Dennis

[godstreasures1]

Thanks so much. I will do that.

[b2001]

The most common place for an air leak is the lid to the hair and lint pot

I had to replace my lint pot lid due to a small crack that had developed - it was along a natural seam and was difficult to spot at first. I was also experiencing reduced pressure problems - and kept going back to the lid, until I finally spotted the problem.

[justinharlow]

I have read this thread with great interest, since I have a 24 foor round AGP and have some questions about my sand fiter. Sounds like you are the people I need to talk to...

I have a Baquapure 2600 sand filter with a 2.5 hp pump. I don't seem to have any leaks or air issues, but I just have this feeling that my filter is not working as well as I think it should be. I backflush like you decribed above (a couple of minutes, till outlet water is clear) a couple of times a week, but my gauge always seems to hover around 19-20 psi. I replaced the sand last summer, but have had a lot of algae problems this spring (we live in Florida, so the algae starts blooming in about March). What pressure should the gauge read in normal operation? If it is higher than it should be, what is the proper drill to get it back in the right range?

Thanks for any help you can offer. :)

Justin Harlow