Air bubbles coming back into lines after blowing them out.

[Isabella]

So I started closing my pool this week and used a shop vac to blow out the return lines. Everything bubbled fine, but then after I plugged them, I noticed little streams of air bubbles still trickling back up into the pool for a good minute or two. Did I not plug them fast enough, or does this mean water might sneak back in over the winter?

 

[Freddie]

So I started closing my pool this week and used a shop vac to blow out the return lines. Everything bubbled fine, but then after I plugged them, I noticed little streams of air bubbles still trickling back up into the pool for a good minute or two. Did I not plug them fast enough, or does this mean water might sneak back in over the winter?

That usually means you didn’t get a perfect seal with the plugs or there was still some residual water left in the line. Sometimes the air pushes back out as it settles. Double-check the plugs are tightened and maybe add Teflon tape to the threads if they’re screw-ins.

 

[Zephyr]

So I started closing my pool this week and used a shop vac to blow out the return lines. Everything bubbled fine, but then after I plugged them, I noticed little streams of air bubbles still trickling back up into the pool for a good minute or two. Did I not plug them fast enough, or does this mean water might sneak back in over the winter?

I’ve had the same thing happen, if the bubbles stop after a while, it’s probably just leftover air escaping, not water sneaking in. The real concern is if you see water creeping back into the line after plugging. A compressor works better than a shop vac too for making sure it’s fully blown out.

 

[Ethan Wells]

What you described actually sounds pretty normal. When you blow the lines out, there’s always a bit of trapped air and moisture that takes a minute to settle. As the pressure equalizes, those last little bubbles work their way up through the water before things fully seal off. It doesn’t necessarily mean your plugs failed or that water is going to sneak back in all winter.

That said, if you want extra peace of mind, you can double-check a couple of things: make sure the plugs are snug and seated properly, and add a dab of pool lube or Teflon tape on threaded plugs to improve the seal. Some people also like to put a bit of antifreeze in the lines as an insurance policy—especially if you’re in a place with deep freezes. Between that and getting a tighter seal, you’ll be covered even if a little air continues to burp out after plugging.

 

[Megan Lawson]

I’ve seen the same thing when closing mine, and most of the time it’s just leftover air working its way out after you plug the return. As long as the bubbles taper off and you don’t see water creeping back into the line, you should be fine.

Tight plugs with a bit of Teflon tape or lube help give a better seal, and if you want an extra layer of protection in freezing areas, a little pool antifreeze in the lines gives peace of mind.

 

[Robert Smith]

That’s actually pretty common and usually not a sign you did anything wrong.

When you blow the lines out with a shop vac, you’re pushing a mix of air and mist through the plumbing. After you plug the return, the pressure inside the line equalises and any trapped air pockets can “burp” their way back out for a short time. That can look like little streams of bubbles for a minute or two, even though the line itself is basically dry.

A couple of things to help you judge it:

• Normal: bubbles that slowly taper off and then stop.
• Not normal: bubbles that keep coming indefinitely or actual water creeping back out of the return.

If the bubbles stopped on their own, you’re likely fine.

For extra peace of mind:

• Make sure the plugs are snug (hand-tight plus a little extra, not overtight).
• Use Teflon tape or a bit of pool lube on threaded plugs to improve the seal.
• If you’re in a colder climate, adding pool antifreeze to the line before plugging gives you a safety buffer in case a tablespoon of water is hiding somewhere.

A compressor does clear lines more aggressively than a shop vac, but plenty of people close successfully with vacs every year. From what you described, this sounds like normal pressure settling, not water sneaking back in over winter.

 

[Diego Rodriguez]

Those little bubbles after plugging are usually just trapped air equalizing in the line and not water sneaking back in, especially if you saw a strong burst when blowing them out, I still like to double check by watching the level and then finishing with something like an aquadoc pool closer winterizing kit to protect everything once I know the plumbing is sealed.

 

[Lily Allen]

The air bubbles coming up after plugging the return lines could be due to trapped air in the pipes, and this usually stops after a minute or two. I’ve had the same experience, and it’s typically not a sign of a leak. However, to be sure, I’d recheck the plugs to make sure everything is sealed properly. If you're worried about potential leaks, I sometimes use AquaDoc Leak Sealer to address that issue.

 

[Alma Weber]

I’ve had the same thing happen, if the bubbles stop after a while, it’s probably just leftover air escaping, not water sneaking in. The real concern is if you see water creeping back into the line after plugging. A compressor works better than a shop vac too for making sure it’s fully blown out.

What you described actually sounds pretty normal. When you blow the lines out, there’s always a bit of trapped air and moisture that takes a minute to settle. As the pressure equalizes, those last little bubbles work their way up through the water before things fully seal off. It doesn’t necessarily mean your plugs failed or that water is going to sneak back in all winter.

That said, if you want extra peace of mind, you can double-check a couple of things: make sure the plugs are snug and seated properly, and add a dab of pool lube or Teflon tape on threaded plugs to improve the seal. Some people also like to put a bit of antifreeze in the lines as an insurance policy—especially if you’re in a place with deep freezes. Between that and getting a tighter seal, you’ll be covered even if a little air continues to burp out after plugging.

From what Zephyr and Ethan described, I’ve seen those small bubbles continue briefly after plugging the returns too. Most of the time it’s just leftover air finding its way out before everything fully settles. As long as the bubbles taper off and you don’t see water creeping back into the line, I’d consider that normal. I usually double-check that the plug is snug and seated properly, then leave it alone. If it stops after a few minutes, I don’t stress about winter issues.