Pump sucking air with vac attached

[wanderingwriter]

Starting a new thread for this, it's been my biggest obstacle in getting my pool open this year. I have debris on the floor of my pool that simply isn't going to come up any other way.

I have my pump and filter operating great. I make sure the water level is high enough that the elbow attachment on the vac plate is fully submerged. I hold the hose up to the intake until it's full of water. It's attached to the vacuum head while both are submerged. There is NOWHERE for air to come from. And yet - at some point, within the first couple seconds/minutes of hooking everything up, the pump will start sucking air. I can watch through the lid as it rapidly drains to about half-full. The water starts spitting out from the intake full of air bubbles. I am completely at a loss to understand WHERE this air is coming from, as every part of the vacuum, hose, and plate attachment are FULLY SUBMERGED IN WATER!

This doesn't happen at any other time, only with the vacuum hooked up. It's just one of those manual triangle-shaped vac heads with a standard hose and pole attached. I've tried three different hoses, one of which is brand new, but I don't see how even a faulty hose could suck in air while it's under-frickin-water.

I have looked up similar problems and found that the answer is usually "you have a leak somewhere in the suction," but I've tried everything to find one and I simply can't.

The suction in the vacuum is usually ok, but I'm afraid to use it for very long with the pump running only half-full. Is it safe to vacuum for any period of time with the pump like this? If not, what can I do to fix this problem? Thanks TFP!

- - - Updated - - -

As a side note, I've tried to force the pump to refill itself by removing and quickly re-locking the lid (a dangerous game if you don't want to get soaked, I know) but it doesn't work. Even without the lid locked on, the pump's not pulling enough water to fill itself. I've also tried manually "priming" it by pouring water in, but it instantly gets sucked through and doesn't raise the water level.

 

[mknauss]

I do not have any experience with Above ground pools but you have a suction side air leak somewhere -- I know it is frustrating but the air has to be coming from somewhere. Try just adding the parts one at a time and see when the suction side leak occurs.

Thanks for posting.

Take care.

 

[wanderingwriter]

You mean the vac parts? It's either the vac plate or the hose that causes it to start sucking air, it varies depending on (who knows? phases of the moon?) Sometimes I'm able to keep the vac plate connected for a while with no issues, other times not. But regardless...I don't know where the air is coming from when the hose is totally in the pool. It just doesn't make sense.

 

[pabeader]

It could be the pump cover gasket. Try applying some gasket lube on it. The head loss is greater through the hose and vac head. This is causing the pump to draw a bit harder then usual and is probably sucking the air in that way. You can test it by hooking up the vac as normal and while it's running, use a garden hose to run water over the lid area. If that is where the leak is, it should go away while the water is on it. Or at least change in some way. Mine did that when i first started using a Sand Shark. A little lube took care of it right away.

 

[Pool Amateur]

I agree with pabeader's assessment above but will add be sure your vacuum head and hose are not blocked, if pump is not getting enough water it is going to try and suck air, water or anything else from somewhere else.

 

[Topher55]

Yep, suction side leak that only shows up with the added resistance of the vacuum. I have gone through this... suction side leaks are tricky to find. Start with the pump lid o-ring clean mating surfaces and lube the print. Then check the unions and their oring. If that doesn't fix it start at the pump and check every fitting working your way to the skimmer. Search this site for more detailed write ups on ways to check, they involve plastic wrap, water hoses, shaving cream. They can be a pain to find.

 

[wanderingwriter]

Thanks for the more detailed explanation - I'm going to take a closer look when I can, and try to find the leak. It's been a busy couple of days and I'm tempted to just give up on opening the pool this year, despite all the work I've put into it so far. It's so frustrating and I don't really have the time or energy for it, but I WANT MY STUPID POOL! lol. My boyfriend keeps reminding me summer is almost over...see if I let him go swimming once I get it figured out.

 

[wanderingwriter]

Okay, so I checked and re-lubed the pump lid and the O-ring and threaded area where the hose from the skimmer attaches to the pump. After doing this, I hooked up the vac and found that it still sucked air, but much SLOWER. After vacuuming a bit I had to detach the vac and re-prime the pump, and that's when I noticed one of those little screw-in outlets in the pump that needed lubing and tightening. I've stirred up a lot of sediment and I need to give the filter a chance to work through it, but I'll try vacuuming again tomorrow if I can and see if the air leak has stopped completely.

 

[pabeader]

Fingers crossed for you!

 

[chiefwej]

Any connection you suspected leaking, wrap with plastic food wrap. If that stops it you've found the leak. Or for a much messier approach,you can smear each one with old fashioned shaving foam and watch for it to appear in the pump pot.

 

[wanderingwriter]

Okay, I found some time to hook up the vac again before I lost the light. Still sucked air - took a while, but it's getting in there somehow. I've already lubed and tightened everything that can be lubed and tightened. All that's left on the suction side, if I'm understanding pump physics correctly, is the connection from the bottom of the skimmer to the hose. It's literally just a hose clamped to the outlet at the bottom of the skimmer - standard fifty cent hardware store hose clamp. It's tightened as tight as it will go, and I already replaced it with a new one this season. Is it possible this is sucking air? If so, how the heck do I fix it permanently?

The other connections I could check are: both ends of pump to filter (both ends of the hose are just clamped on like I describe above), and both ends of filter to intake. The filter-to-intake hose on the filter side has one of the fancy screw-on connectors with an O-ring and a ball valve, but I don't think ANY of these qualify as being on the "suction side," am I right?

Anyway....if I have time tomorrow I'll try the plastic wrap trick. Hopefully I'll at least be able to get the vac running for more than a few minutes.