How does water evaporation from the pool work when it comes to cold temps? Will it evaporate when when the water is in the 50's and 60's? Does it gradually just diminish the amount it will evaporate until it hits the freezing point?
water loss to evaporation at cold temps
- Thread starter camueller
- Start date
- May 23, 2015
- 24,495
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
It all depends on the air temperature and relative humidity versus the water temperature. If air and water temperatures are close, and the air is not too dry, evaporation will be minimal. You can start at this article over at The Engineering ToolBox to get a feel for what's involved -
Evaporation from Water Surfaces
Evaporation from Water Surfaces
Cameuller, if you're asking because you're trying to work out late season energy consumption to heat in a northern clime, check out this link. I've found the calculator quite accurate so far 
SWIMMING POOL ENERGY TEMPERATURE CALCULATOR | Neil Anderson
SWIMMING POOL ENERGY TEMPERATURE CALCULATOR | Neil Anderson
Very interesting info. Thanks all, I will be reading through this today/tonight. None of it is all that important, I was just curious. My plan this year is to winterize my pump and plumbing in my pool, but leave the pool uncovered. I'm not even going to lower the water level except to backwash my sand filter.
last year (the only other winter that I've owned this house/pool) I drained it about a foot and a half, and then kept having to bail rain water out. Even with all that water loss, my CYA level was 160 when i opened, due to previous owner's use of trichlor pucks. This year I'm going into winter with a CYA of 50 and I'm just curious what I'll come out in Spring with. I expect that even though I'm not draining a bunch right off the bat, i will be draining plenty throughout the winter months with rain and snow melt, so I should be flushing some CYA and salt down the storm drain. How much though I'm anxious to see, and therefore theorizing.
last year (the only other winter that I've owned this house/pool) I drained it about a foot and a half, and then kept having to bail rain water out. Even with all that water loss, my CYA level was 160 when i opened, due to previous owner's use of trichlor pucks. This year I'm going into winter with a CYA of 50 and I'm just curious what I'll come out in Spring with. I expect that even though I'm not draining a bunch right off the bat, i will be draining plenty throughout the winter months with rain and snow melt, so I should be flushing some CYA and salt down the storm drain. How much though I'm anxious to see, and therefore theorizing.
yup, water will evaporate in the 50's, 60, any temp really.
Water freezing point isn't the bottom (temp) threshold either. Ice will sublime and eventually disappear (without turning into "water") as long as the air is below 100% humidity. Leave some ice cubes in your freezer for a while and you can see the pieces get smaller and eventually disappear over time.
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borjis
LifeTime Supporter
In the off season I never have to top up...but I do have to drain several times from rain.
That makes sense, based off the information JoyfulNoise provided. Where I live (Southern IL, St Louis area) winter doesn't get extremely cold, but we do normally get a good week to 3 of below freezing temps for highs. I don't know what my water temps will be, but I suspect more often than not the water temp and the air temp are going to be fairly close (in the 50's for both most of the time) so evap should be slower than rain gain.
In hindsight, I guess what I was really wondering was whether covering it in the winter helped keep evaporation down. While I am sure that it does, I don't think it is not enough of a concern to change my plans of not covering.