Turning green with cold water

[cj133]

As some may recall I stopped covering my pool in the winter.
I let the pump run in low speed 24/7 until the water gets into the low to mid 30s, and then shut it down and drain the filter etc. This usually takes place around Thanksgiving / early December.

Then, I open as soon as I can which is usually some time in March, but this year I had to start up earlier than I expected as I noticed my walls were turning green even with ice still on top of the water. I was a bit surprised because I thought cold water wouldn't grow anything? Unless the water below the ice was much warmer than I thought.

Pump running in low with some ice floating around.

As soon as I noticed the green walls I brought my fc up to 15ppm as I started filling to get the pump running, most of the green was gone by the time I took that video. After a few days I'll start working on my pH as well as things stabilize with the pump running.
I have most of the leaves out now as well. I keep it clean until it freezes and then it's kind if impossible to get leaves out because they end up in the ice.

So far, I'll still take this method over the cover baloney and this is my 3rd or 4th season doing it this way

 

[JoyfulNoise]

There are all types of algae, even species of algae that grow in very cold, near freezing water. Temperature simply affects the RATE at which algae grows, not so much an on/off thing. And yes, there may be ice on the surface but the water below can easily be a bit warmer than that as the solid ice acts as a thermal barrier. The main determinant for algae growth is going to be chlorine levels and yours are probably low enough or zero and so algae can start to grow, albeit very slowly.

Just SLAM the pool and it will go quickly. The chlorine you add will kill the algae fast and the water will clear up quick. Better now than if it were warmer where you’d be fighting more of an uphill battle.

 

[Mdragger88]

The deal is that there’s simply not enough chlorine. As Matt mentioned, cold slows algae growth but it doesn’t stop it completely.
Using a cover prevents the chlorine you add at closing from being consumed by the sun and also debris whilst the pool is asleep for the winter. In lieu of a cover for protection you may need to consider “closing” at slam level if you aren’t already & reupping/checking that periodically throughout the closed period. Those with mesh type covers often find the need to also use polyquat as insurance against low fc conditions for a short period which may or may not be of some benefit to you.
I am in a bit of a different climate but I fully close around Halloween/early November at slam level with a solid tarp style cover and check my fc around Christmas before the pool freezes as we get crazy heat waves and then check again in late feb after things thaw. I have never needed to add fc but I am always prepared to do so. I generally do a soft open (running the pool with the cover on) in late march & don’t uncover a for few weeks- a month later.

 

[cj133]

The deal is that there’s simply not enough chlorine. As Matt mentioned, cold slows algae growth but it doesn’t stop it completely.
Using a cover prevents the chlorine you add at closing from being consumed by the sun and also debris whilst the pool is asleep for the winter. In lieu of a cover for protection you may need to consider “closing” at slam level if you aren’t already & reupping/checking that periodically throughout the closed period. Those with mesh type covers often find the need to also use polyquat as insurance against low fc conditions for a short period which may or may not be of some benefit to you.
I am in a bit of a different climate but I fully close around Halloween/early November at slam level with a solid tarp style cover and check my fc around Christmas before the pool freezes as we get crazy heat waves and then check again in late feb after things thaw. I have never needed to add fc but I am always prepared to do so. I generally do a soft open (running the pool with the cover on) in late march & don’t uncover a for few weeks- a month later.

I maintained my fc until I closed, and literally the day I shut the pump down the top of the pool froze, which is typical for me. I try to hold out as long as I can. But, I'm fairly certain my level was fairly low, like 4-5ppm. That was my first mistake.

What I haven't figured out is how I'm supposed to add bleach while the top is frozen. There's days where I get it to thaw so I can fit a finger between the liner and ice, but the ice was a good 8"+ thick. Would it be acceptable to pour bleach down that crack and just hope for it to mix on it's own over time?

Of course, as it started to thaw over the past week or two I could've done much better. I'd glance out and see ice on it, so I kept ignoring it, assuming the water was plenty cold. That almost bit me real good I guess.

 

[Mdragger88]

I maintained my fc until I closed, and literally the day I shut the pump down the top of the pool froze, which is typical for me. I try to hold out as long as I can. But, I'm fairly certain my level was fairly low, like 4-5ppm. That was my first mistake.

What I haven't figured out is how I'm supposed to add bleach while the top is frozen. There's days where I get it to thaw so I can fit a finger between the liner and ice, but the ice was a good 8"+ thick. Would it be acceptable to pour bleach down that crack and just hope for it to mix on it's own over time?

Of course, as it started to thaw over the past week or two I could've done much better. I'd glance out and see ice on it, so I kept ignoring it, assuming the water was plenty cold. That almost bit me real good I guess.

If you’re closing at 4/5 ppm that won’t last long without a cover. Heck, that won’t last long even with a cover.
Raise to slam before turning every thing off. Some people also throw in a floater but i worry about it cracking and dropping the tabs or getting stuck somewhere (you could tether it).
If the water is frozen there’s not much you can do. You should only add liquid chlorine if you’re able to mix the water (with a brush or pump)
You shouldn’t disturb ice in a pool it could rip the liner.

 

[JoyfulNoise]

Yeah, never mess with a frozen pool. The ice on the surface can do a lot of damage if you try to break it up. It's better to just close the pool as best you can and forget about it until the spring. There's no way to add chlorine safely to a winterized pool and no way to circulate the water so it's all just a futile effort that will likely result in more harm than good.