Advice on running pool heater for a day ahead of polar vortex

[DB-Cooper]

My water is currently 45F. We've got a few days of cold coming, like teens overnight and barely hitting above freeze during the day. The storm is extremely similar to what we faced in December 2022. That said, my water starting temperature was closer to 50F for that storm. I hit 36F water temp at the lowest. The December 2022 winter weather was arguably a little colder, but I had warmed days in front of it, hence the higher starting point.

I'm debating running the heater now to get to 55-60F just to buy me extra residual water temp. I compared weather history with water temp.

That said, I know running cold water through a heater had a condensation/corrosion concern, any tricks to mitigate that. Other option is to let freeze protection do it's thing, I am tarping with lights. Presumably being salt I get a tiny buffer under 32F and I can keep the water running pretty good. As my pool is semi-above ground, I don't get as much earth/thermal protection and it is generally facing the direction of the wind.

Today is reasonably warm hitting 71-72F and overnight temps tonight are good, it goes downhill after that. Again, considering running the heater just during these better days to get me 10 degrees or so, then shut off and let freeze protection go. I can switch to Spa mode and get the water temp real hot if it helps with the condensation issue.

Thoughts?

 

[Bperry]

My water is currently 45F. We've got a few days of cold coming, like teens overnight and barely hitting above freeze during the day. The storm is extremely similar to what we faced in December 2022. That said, my water starting temperature was closer to 50F for that storm. I hit 36F water temp at the lowest. The December 2022 winter weather was arguably a little colder, but I had warmed days in front of it, hence the higher starting point.

I'm debating running the heater now to get to 55-60F just to buy me extra residual water temp. I compared weather history with water temp.

That said, I know running cold water through a heater had a condensation/corrosion concern, any tricks to mitigate that. Other option is to let freeze protection do it's thing, I am tarping with lights. Presumably being salt I get a tiny buffer under 32F and I can keep the water running pretty good. As my pool is semi-above ground, I don't get as much earth/thermal protection and it is generally facing the direction of the wind.

Today is reasonably warm hitting 71-72F and overnight temps tonight are good, it goes downhill after that. Again, considering running the heater just during these better days to get me 10 degrees or so, then shut off and let freeze protection go. I can switch to Spa mode and get the water temp real hot if it helps with the condensation issue.

Thoughts?

If it were me, I’d drain the equipment pad. You can’t count on freeze protection when the daytime high is that close to freezing and if you get a power outage like last time it’s bad news. Maybe you get lucky though and it won’t be that bad?

 

[DB-Cooper]

If it were me, I’d drain the equipment pad. You can’t count on freeze protection when the daytime high is that close to freezing and if you get a power outage like last time it’s bad news. Maybe you get lucky though and it won’t be that bad?

This storm again mirrors what we had last year, and as long as we keep power, it can survive. That said, I'm home the entire time and if we lose power, I know exactly how to drain this stuff quickly.

 

[Newdude]

This storm again mirrors what we had last year, and as long as we keep power, it can survive

From the best I can tell with google, its just a cold snap. If it was a storm that hit during a cold snap, power outages would be a much bigger concern.

You're basically where I am every spring when i open early. The 40s/50s weather can easily turn a couple weeks later and get cold again. But without snow, sleet or ice in the forecast with it, i'd be totally comfortable running the pump on high throughout.

If you've already done a trial run once or twice to drain your equipment, your backup plan is covered. You'd MUCH rather stumble through it when it's nicer out so it's second nature when spit hits the fan.

 

[gkw4815]

If you're going to run your heater, I'd do it now and then switch it off before the cold snap begins. It's possible that gas grid conditions could be tight with everyone heating their homes at once.

I'm not planning to run my heater, because of this issue and because of the corrosion concerns.

Your pool and view are awesome btw.

 

[DB-Cooper]

From the best I can tell with google, its just a cold snap. If it was a storm that hit during a cold snap, power outages would be a much bigger concern.

You're basically where I am every spring when i open early. The 40s/50s weather can easily turn a couple weeks later and get cold again. But without snow, sleet or ice in the forecast with it, i'd be totally comfortable running the pump on high throughout.

If you've already done a trial run once or twice to drain your equipment, your backup plan is covered. You'd MUCH rather stumble through it when it's nicer out so it's second nature when spit hits the fan.

First hand, real-world experience in February 2021

There's some risk of some light freezing drizzle Monday morning, but nothing intense, they're not predicting that drizzle to weigh down on trees, etc.

 

[DB-Cooper]

If you're going to run your heater, I'd do it now and then switch it off before the cold snap begins. It's possible that gas grid conditions could be tight with everyone heating their homes at once.

I'm not planning to run my heater, because of this issue and because of the corrosion concerns.

Yeah, it's run it now to gain 5-10 degrees and then shut it down tonight/tomorrow and let it run. I'm not sure I understand the corrosion issue. I read things about low air temp being the issue (air temp is good today/tnoight). Then I read about low water temps. I also read it's fine as long as you continue to heat it (like in a spa). If it's just about burning things off, I can finish on a spa run and get it up to the 90s or what not.

 

[JJ_Tex]

Trust your freeze protection and have a plan ready to execute in the event of power or equipment failure.

I wouldn't mess with the heater. Keep in mind that any issues would come from water standing still in pipes or equipment and allowing to freeze and expand. Using your heater to bump up the water temp by say 10-20 degrees will only buy you a couple of minutes and not worth it. Think about it this way... if you put 2 bottles of water in your freezer and 1 was 10 degrees warmer, they will still freeze in roughly the same amount of time. Same goes for water in your pipes.

 

[DB-Cooper]

Trust your freeze protection and have a plan ready to execute in the event of power or equipment failure.

I wouldn't mess with the heater. Keep in mind that any issues would come from water standing still in pipes or equipment and allowing to freeze and expand. Using your heater to bump up the water temp by say 10-20 degrees will only buy you a couple of minutes and not worth it. Think about it this way... if you put 2 bottles of water in your freezer and 1 was 10 degrees warmer, they will still freeze in roughly the same amount of time. Same goes for water in your pipes.

Thanks. Water bottles by volume aren't huge, pools are. Shedding 10 degrees could buy 12 hours, who knows.

As my water temp hit 34F last time we had a similar (arguably a little colder/longer), if things stay running, what happens if water hits say 30F (and it's moving). I have aggressive fountains that dump quite a bit of water into the pool causing significant wake, etc. I guess when does running water really freeze, it's a complicated question above my science grade.

 

[W.J.Christy]

Y'all are making me nervous. Houston should be ok, but I am still worried.

.

 

[JJ_Tex]

Thanks. Water bottles by volume aren't huge, pools are. Shedding 10 degrees could buy 12 hours, who knows.

As my water temp hit 34F last time we had a similar (arguably a little colder/longer), if things stay running, what happens if water hits say 30F (and it's moving). I have aggressive fountains that dump quite a bit of water into the pool causing significant wake, etc. I guess when does running water really freeze, it's a complicated question above my science grade.

Right, but your entire pool volume isnt going to be stagnant in your pipes/equipment... its only going to be a few cups of water in each piece of equipment. Those few cups will freeze in the same amount of time, regardless of running the heater now or not.

Running your heater now should not hurt anything, so feel free to do it, but I'm just cautioning that it will not offer much protection for you and may even increase evaporation requiring you to refill the pool during freezing temps.

I do not have a scientific answer to your last question, but running water will not freeze at the temps we going to see. Back in snowmageddon we were substantially lower (-2 for us) and for a much longer duration than these 2-3 days upcoming. The pools here that kept power did not have any issues, only people who lost power and did not properly drain their equipment before it froze.

 

[DB-Cooper]

Right, but your entire pool volume isnt going to be stagnant in your pipes/equipment... its only going to be a few cups of water in each piece of equipment. Those few cups will freeze in the same amount of time, regardless of running the heater now or not.

Running your heater now should not hurt anything, so feel free to do it, but I'm just cautioning that it will not offer much protection for you and may even increase evaporation requiring you to refill the pool during freezing temps.

I do not have a scientific answer to your last question, but running water will not freeze at the temps we going to see. Back in snowmageddon we were substantially lower (-2 for us) and for a much longer duration than these 2-3 days upcoming. The pools here that kept power did not have any issues, only people who lost power and did not properly drain their equipment before it froze.

Snowmageddon had significant falling snow too which hits the pool and has to melt and cools things even more. As stated, I survived last year (and I was out of town). My pool is only half in the ground as it's built into a hill. Compared to friends nearby, my pool lacks a bit of the earth heat retention and is more open to the wind. My temps seem to fall a bit faster.

 

[DB-Cooper]

I do not have a scientific answer to your last question, but running water will not freeze at the temps we going to see. Back in snowmageddon we were substantially lower (-2 for us) and for a much longer duration than these 2-3 days upcoming. The pools here that kept power did not have any issues, only people who lost power and did not properly drain their equipment before it froze.

Found a cool explanation on this Reddit thread, a bit more scientific:

https://www.reddit.com/r/NoStupidQuestions/comments/18c730t

"I’ll give you a simple example. I used to work on a remediation prospect cleaning up a lake, which would continue into winter. Under normal circumstances, the lake would freeze entirely over with enough ice that you could safely walk across it. However, we still needed to continue work during the winter and had equipment remain in the water. To protect that equipment from ice damage, we installed agitators around them, which sloshed the surface a bit. If you turned the agitators off, the water would very quickly freeze over again. So what gives? The water wouldn’t suddenly drop in temperature, as the agitators would have only produced a marginal amount of residual heat.

So, what the agitators do is introduce energy into the system. This causes the water molecules to continue to move and scatter, preventing them from aligning and forming the rigid structure needed to produce ice. So water can be a much cooler temperature than the freezing level, but as long as energy is still present in the system, it does not freeze (unless you’re changing variables like pressure or supercooling, but those are complications we don’t need to worry about right now).

Natural bodies of water are rarely static systems. Even within a frozen river, the water beneath the surface is still moving, which is why the whole thing doesn’t turn into a glacier every winter. Even lakes are not static systems. Most lakes have a degree of thermal stratification, which means the temperature is not consistent throughout. Because heat rises and cold sinks, it creates a natural cycle of water within the lake, constantly moving those water molecules up and down. The reason the tops of lakes and rivers freeze over is due to an open exchange of heat, where the water can expel its energy into the atmosphere through that heat exchange. Once a layer of ice forms, it becomes more difficult for the body of water to continue to expel that energy, so water beneath the ice can still get to temperatures below freezing without being frozen."

 

[1poolman1]

My water is currently 45F. We've got a few days of cold coming, like teens overnight and barely hitting above freeze during the day. The storm is extremely similar to what we faced in December 2022. That said, my water starting temperature was closer to 50F for that storm. I hit 36F water temp at the lowest. The December 2022 winter weather was arguably a little colder, but I had warmed days in front of it, hence the higher starting point.

I'm debating running the heater now to get to 55-60F just to buy me extra residual water temp. I compared weather history with water temp.

That said, I know running cold water through a heater had a condensation/corrosion concern, any tricks to mitigate that. Other option is to let freeze protection do it's thing, I am tarping with lights. Presumably being salt I get a tiny buffer under 32F and I can keep the water running pretty good. As my pool is semi-above ground, I don't get as much earth/thermal protection and it is generally facing the direction of the wind.

Today is reasonably warm hitting 71-72F and overnight temps tonight are good, it goes downhill after that. Again, considering running the heater just during these better days to get me 10 degrees or so, then shut off and let freeze protection go. I can switch to Spa mode and get the water temp real hot if it helps with the condensation issue.

Thoughts?

Run you pump at night, at least from 2:00AM until 8:00AM, if it is a single-speed pump. With a VSP, just let it run at a medium speed 24/7, and you should have no issues. Our temps here have been similar to yours, 34 last night. My pump has been running a schedule like above for 34 years, even when we had temps of 18 degrees in 1990, it would "warm" to the low 30s and have never had an issue. Just knew it was coming and prepared accordingly.

You don't want to run your heater with water that cold.

 

[DB-Cooper]

Run you pump at night, at least from 2:00AM until 8:00AM, if it is a single-speed pump. With a VSP, just let it run at a medium speed 24/7, and you should have no issues. Our temps here have been similar to yours, 34 last night. My pump has been running a schedule like above for 34 years, even when we had temps of 18 degrees in 1990, it would "warm" to the low 30s and have never had an issue. Just knew it was coming and prepared accordingly.

You don't want to run your heater with water that cold.

Well we go below 18 from time to time, we may hit 14 or so this time, but only briefly. We're going to do the roller coaster of teens to low 30s to teens to low 30s for 2-3 days.

I have a variable pump and let it ride at 30 GPM, it adjusts that flow on both the pool and spa (spa needs more RPM).

 

[generessler]

Note that for many heaters running with low temp water for extended periods may be bad. My manual says "OPERATING THIS HEATER CONTINUOUSLY AT WATER TEMPERATURE BELOW 68° F. WILL CAUSE HARMFUL
CONDENSATION AND WILL DAMAGE THE HEATER AND VOID THE WARRANTY." I don't know what "continuously" means in this context. A day? Month? Year?

The other thing is that hitting 32F does not mean the pool becomes a block of ice. There is latent heat of freezing to be dumped first. That's hard if the water is moving. In '22 our pool hit 32F for about 48 hours after four consecutive freezing days and ~10F nights. The last morning there was a skim of ice in the middle. That's it. I was told here that if it had stayed cold the skim would have grown thicker, and the thing to watch most carefully was skimmers.

 

[DB-Cooper]

Note that for many heaters running with low temp water for extended periods may be bad. My manual says "OPERATING THIS HEATER CONTINUOUSLY AT WATER TEMPERATURE BELOW 68° F. WILL CAUSE HARMFUL
CONDENSATION AND WILL DAMAGE THE HEATER AND VOID THE WARRANTY." I don't know what "continuously" means in this context. A day? Month? Year?

The other thing is that hitting 32F does not mean the pool becomes a block of ice. There is latent heat of freezing to be dumped first. That's hard if the water is moving. In '22 our pool hit 32F for about 48 hours after four consecutive freezing days and ~10F nights. The last morning there was a skim of ice in the middle. That's it. I was told here that if it had stayed cold the skim would have grown thicker, and the thing to watch most carefully was skimmers.

Thanks, yeah that condensation thing is sort of what I was confused by. People heat hot tubs all the time from water temps below 68. I figured a few hours wouldn't hurt and finishing it off in spa mode would let it get well above 68. I recall reading in previous threads something to the effect is that if you start the heater, you need to keep it running until you get to ~70F.

We'll see how this cold snap does for us!

 

[1poolman1]

Thanks, yeah that condensation thing is sort of what I was confused by. People heat hot tubs all the time from water temps below 68. I figured a few hours wouldn't hurt and finishing it off in spa mode would let it get well above 68. I recall reading in previous threads something to the effect is that if you start the heater, you need to keep it running until you get to ~70F.

We'll see how this cold snap does for us!

A stand-alone hot tub/spa uses a different type of heater, an immersion electric heating element that the water runs over in a sealed tube.
A pool with a gas heater will form a lot of condensation on the heat exchanger that will then drip onto the burners and rest of the combustion chamber. Condensation like that has a very low pH, usually between 2.9 and 4. Add the heat from combustion and it will eat the metals very quickly.

 

[6XSBChamps]

If I did get to the point where I need to drain the pad due to loss of power etc, should I also try to get the waterline lowered below the skimmer ?

 

[DB-Cooper]

A stand-alone hot tub/spa uses a different type of heater, an immersion electric heating element that the water runs over in a sealed tube.
A pool with a gas heater will form a lot of condensation on the heat exchanger that will then drip onto the burners and rest of the combustion chamber. Condensation like that has a very low pH, usually between 2.9 and 4. Add the heat from combustion and it will eat the metals very quickly.

My point was that many people use their hot-tub (in a built-in pool) in the winter with starting temperatures pretty low. Granted, it doesn't run for hours/days on end with low water temperatures and it always finishes very hot. I wish we used our hot tub more in the winter, but probably 2-3 times per year I fire that thing up and the water temperature is anywhere in the 40s-50s in the winter; 45 minutes later we're in it for maybe an hour. I feel this is a very common use case, as opposed to letting it run days on end, and/or heating it for a weekend, letting it cool and repeating again for days of usage.