Will black winter cover/tarp keep water warmer for spring opening?

AndyTN

Bronze Supporter
Mar 27, 2019
407
Memphis
Pool Size
26000
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Vinyl
I would like to get some comments on something I tried last year and felt it helped but could have all been in my head. If my winter tarp is flipped from silver to the black side up, will this act like a solar heater to warm up my water 10 degrees or so? Assume my water level is near the bottom of the skimmer so basically the entire pool surface area is touching the tarp and I am keeping it relatively clean with most water pumped off. I close my pool completely during winter since we get several random nights below freezing so no circulation is happening during winter. In the South, we get many sunny days during winter and have random warm patterns getting up into the 60-70's all winter. I assume the black will technically absorb more heat than the silver, which will reflect the sun's rays, but would I actually see a difference?

Also, a slightly separate discussion to the same topic. I have several oak trees over my pool which vomit a bunch of stuff into the pool every April during bloom so this year I left the black cover on for several weeks after technically opening the pool with pump circulating water several hours per day. I have used my solar cover in previous years during April which helped warm the pool but all the Crud falling out of the oak trees got into the water causing tannin stains. Will be black cover still heat the pool water the same as having the solar cover on? Both would prevent evaporation and the black surface will be absorbing heat from the sun with circulating water under it.

Feel free to dismiss the black tarp vs. solar cover but I don't see why the black tarp all winter would hurt anything even if it didn't warm the water more than a degree. I also don't have a good area for a solar system how my roof is shaped and where my pool is situated in our yard with lots of tree cover.
 

ajw22

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Jul 21, 2013
29,782
Northern NJ
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You want winter pool water to be below 60. Cold water will not grow algae so you don’t need to check chlorine levels. The black cover can warm water at the surface and allow algae to grow against the cover.

Why do you care about raising your water temperature once your pool is closed?
 

AndyTN

Bronze Supporter
Mar 27, 2019
407
Memphis
Pool Size
26000
Surface
Vinyl
It's all about start-up temperature and being able to get into the pool when we have warm days during late March and April. The difference in 75 vs 65° water at opening is the difference for whether or not someone can swim comfortably. I don't have a good area for solar panels and I don't want to spend the money on a heater when I am trying to cool off my water half the season. Just trying to see if I would actually get any free additional warming from the black tarp acting as a large solar panel.

Also, I understand the cold water preventing algae but how would algae grow if the solid tarp is preventing any sunlight from hitting the water? Algae is a plant which needs sunlight to grow.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
29,782
Northern NJ
Pool Size
35000
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Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Also, I understand the cold water preventing algae but how would algae grow if the solid tarp is preventing any sunlight from hitting the water? Algae is a plant which needs sunlight to grow.

Ask that question to all the people who open their pools late and find green swamps. Happens every year.
 
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Vangar2012

Member
Jun 10, 2016
24
Farmington KY
AndyTN, just curious if you ever got your pool warm in the Spring. We are in the same predicament. Live in west KY and would like to start warming the pool in April and May but the stuff falling from the trees make it impossible to use our solar cover during this time. I’m toying with using our black coil hose heaters my husband made (we call them Redneck Heaters) while I still have the winter cover on. IMO, it wouldn’t raise the temp so extreme to cause algae growth. Just curious if you ever tried anything!
 

AndyTN

Bronze Supporter
Mar 27, 2019
407
Memphis
Pool Size
26000
Surface
Vinyl
This post is almost 2 years old and I have learned a lot more in that amount of time. I still keep on the black tarp until mid-April due to all the stuff falling out of my oak trees. What I have done is start running the pump and getting the water balanced in late Feb or early March. The FC in the water will prevent any algae concerns on the tarp. When the sun is shining bright on the pool, I will turn on the pump with the returns pointing slightly up to get a lot of flow on the back of the tarp. At night when it is cold or on a cloudy day, the pump is off just as it would be still closed.

Another thing I do with this is to use the tarp to keep out the cold rain when we have one of those spring storms dumping 2-3 inches. That can really cool down the pool if that cold rain goes right into the water and you can pump it off during the storm. You also need to keep the black tarp as dry as much as possible because evaporating water from the top of the tarp will steal your heat from the sun. I do not have a good area to put solar panels for a real solar heater so I have 300 feet of garden hose laid out over my rock-landscaped area which gets a lot of sun. The hose gets a little solar irradiation but the rocks also warm up in the sun which helps heat up the hoses from the bottom.

The only reason I am going to these extremes is because my wife will not allow me to get a heater. She likes the 5-month break from the pool when it is closed and if she allows me to get a heater, she thinks I will try to keep it open/heated year round. Through all my antics, I was able to get the pool up to 74 a week ago. The past week has been cool and it is back down to 72. These temps are just barely warm enough for my kids and I to take a chilly 5-10 minute swim but nothing like it would be if I actually had a heater. I am done with the tarp for the season and now have the solar cover on, staying on until mid-May.
 
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JW1

Well-known member
Sep 4, 2019
201
SW Ohio
What factors do you use to finally add the solar cover to the spring pool water? Certain water temp? Trees done blooming? Air temperature at night? Or just tired of the tarp?
 
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