How does pool overflow work?

[pcm2a]

In Tennessee it has rained for over 24 hours straight from the hurricane aftermath. I've never seen the pool this full, which was neat. The thing is it reached this level after about 6-8 hours and then it consistently rained forever. I thought I was finally going to see the pool overflow onto the ground. However, it never went higher than this. That's when I realized there must be some sort of overflow protection, but I have no clue how it works. There is no extra "hole", like a bathtub, for water to escape at the top of the skimmers. Thanks for any insights!

 

[Lake Placid]

Any unexplained holes or covers in the pool shell? Overflows don’t have to be installed in tandem with the skimmer.

 

[pcm2a]

No holes at that height around the gunite. No holes in the skimmers, at least where I can see straight down. No holes in the auto-fill, which is plugged in the pool and much deeper (I have no auto-fill hooked up).

My gutters and pool filter empty into a series of pipes underground that go way out in the yard. Is it possible that if the water gets high enough it is utilizing this system to let the water out? The problem there are two ports that I can check or use for unclogging things. If water was going out there, it was also with the gutter water, so hard to check.

 

[Bperry]

No holes at that height around the gunite. No holes in the skimmers, at least where I can see straight down. No holes in the auto-fill, which is plugged in the pool and much deeper (I have no auto-fill hooked up).

My gutters and pool filter empty into a series of pipes underground that go way out in the yard. Is it possible that if the water gets high enough it is utilizing this system to let the water out? The problem there are two ports that I can check or use for unclogging things. If water was going out there, it was also with the gutter water, so hard to check.

It’s likely the deck and skimmers are not sealed and so excess water leaks under the decking. Don’t let it do that or lots of damage can occur.

 

[pcm2a]

I ran the waste and lowered it down to be safe. Around the pool is flagstone on top of concrete, and this would be a tremendous amount of water. Around 20k gallons total pool size, just guessing at least 2 inches worth of water that should have filled up but instead disappeared. The concrete could absorb that much water? That is terrifying to think about.

Attached is a picture of one of the skimmers. Another interesting thing, after the rain slowed, I expected the water to remain at the level of the first picture, but it lowered a little more (before I ran the waste at the filter). Attached is a picture of its final resting place after water went somewhere. Temperature was in the upper 60s/low 70s, so not hot enough for that amount of evaporation in a very short amount of time.

 

[TinFoilHat]

It doesn't soak into the concrete because that isn't possible but it will seep under the decking and cause problems. That's what you want to avoid.

 

[Bperry]

It doesn't soak into the concrete because that isn't possible but it will seep under the decking and cause problems. That's what you want to avoid.

This ^, it soaks through any cracks or gaps in the concrete into the surrounding soil behind it. It can even soak through the concrete shell of the pool if there’s a crack in the plaster.

Your skimmer looks different than mine and looks to be a single piece so no gap to soak through in that case.

 

[Dirk]

It’s likely the deck and skimmers are not sealed and so excess water leaks under the decking. Don’t let it do that or lots of damage can occur.

I was about to say the same. If you don't know where the water is going, it's not going anywhere good! It could be running into some gopher hole, washing away dirt from around your pool, or from under your deck, or even from around your home's foundation. All bad.

Pump the water out manually before it gets that high, at least until you solve the mystery.

If there was an actual overflow system, it would be obvious. Either a hole or grate in the edge tile, a hole lower in your pool wall, or a hole in your skimmer. That's about it. They don't hide them, because you have to maintain them: clear them of crud and leaves, etc. Mine once got plugged up at the exit end! Plants started growing into the pipe and sealed it up. Took me a while to realize what was happening and why my pool was so high. Der!

Mine is an equalizer tube (a hole lower in my pool wall), that connects to an auto-leveling system. But those are obvious, too. They have a lid, similar to your skimmer's lid, and are usually somewhere in your deck. Mine is right next to my skimmer. They can be elsewhere, like up to 30' away, but that's not common. If the holes underwater all all returns, or maybe one vacuum port and the rest returns, you don't have an equalizer tube system.

If you don't know how to manually control your overflow level, just ask. We'll sort you out.

 

[Mdragger88]

Most pools that are plumbed with an autofill also have an overflow. I suspect you may have one you just haven’t found it. Definitely do as Dirk said and handle it manually until you are certain you have one.

 

[pcm2a]

Roger that on manually handling it. Normally I do the waste whenever it gets close to no gap, always keeping at least an inch. The only reason I didn't rush out this time was to see the pool fill up. This is the first time in 8 years it got that high. I do have a place for the autofill valve, although no float device is in it. It's plugged from the inside of the pool but it's much too low to be an overflow.

 

[Lake Placid]

Check your autofill for additional ports. In your case it’s not working because it’s plugged poolside. However a number of autofills will have an extra port that will allow excess water out. Since water seeks its own level, the water in autofill will equalize with the pool water and excess will flow out the overflow port in the autofill.

 

[Dirk]

Roger that on manually handling it. Normally I do the waste whenever it gets close to no gap, always keeping at least an inch. The only reason I didn't rush out this time was to see the pool fill up. This is the first time in 8 years it got that high. I do have a place for the autofill valve, although no float device is in it. It's plugged from the inside of the pool but it's much too low to be an overflow.

The overflow outlet in your auto-fill well might not be obvious, and wouldn't necessarily be near the top of the well. Mine is a vertical tube, the top of which is level with the pool's water level. But if your tube is missing, the port that tube would connect to is at the bottom of the well. Look for a port on the bottom, maybe it has a plug of some sort in it.

There are auto-fill wells that don't have any overflow function. So if you don't see a port for it, that's not uncommon.

PS: note that even if there is a port for an overflow tube on the bottom of the well, that doesn't mean the original builder ever connected it to anything.