It is currently December 8th, 2013, 5:33 pm

 All times are UTC - 6 hours [ DST ]

 Page 1 of 1 [ 8 posts ]
 Print view Previous topic | Next topic
Author Message
Post subject: water evaporation rate formula ??
Posted: May 1st, 2007, 7:12 pm
 In The Industry & Supporter

Joined: April 22nd, 2007, 2:08 am
Posts: 17
Location: Jacksonville, Florida
Anyone ever heard or know of an acurate formula for calculating evaporation rate of a pool ?
I am certain it depends on air temp, water temp, RH, agitation, air movement, disolved solids in water, etc, so I am sure it isn't an easy one, but this has really peaked my curiosity, especially here in NE FL with the drought conditions (RH between 20 and 25% with highs at 88 to 90) I have watched the water level drop almost 2 inches in less than a week. I do not have any leaks, and haven't backwashed (used the bucket on the ladder trick to verify)
any thoughts ?
figured this was a "geeky" question so I posted it here in the chem side...

_________________
http://pg.photos.yahoo.com/ph/dj71datsu ... r=/562fre2

Post subject:
Posted: May 1st, 2007, 7:15 pm

Joined: April 3rd, 2007, 8:50 pm
Posts: 278
Location: East Tennessee
I think a that would be hard to predict and the math would change day by day. You may want to think about using a cover of some type to prevent evaporation.
Steve

_________________
Echo Canyon II by Artesian Pools, 13.5 KGal AG Round, 22" Artesian Sand Filter 2 hp Artesian pump
Med Lab Tech for 12 years in E.TN
Chem testing by Trouble Free Test Kits

Post subject:
Posted: May 2nd, 2007, 6:35 am

Joined: April 4th, 2007, 10:08 am
Posts: 6729
Location: SW Indiana
Pretty tough one to calculate. You'd have to consider humidity, wind speed, air temp, water temp, cloud cover, maybe even sun angle among other things. You'd have to update the calculation as conditions changed.

Post subject: there in lay the challenge !!!
Posted: May 2nd, 2007, 11:21 pm
 In The Industry & Supporter

Joined: April 22nd, 2007, 2:08 am
Posts: 17
Location: Jacksonville, Florida
I have found a few sites that discuss this, but I am not a scientist, nor chemist, so I mainly pose this question for theory and discussion. I am aware the only way to prevent, or at least slow down evap is to cover, I was just pondering if anyone had seen or developed a formula that took to count the above mentioned variables, and a few we may not be considering. (i.e. disolved solids, ph, etc.)

_________________
http://pg.photos.yahoo.com/ph/dj71datsu ... r=/562fre2

Post subject:
Posted: May 24th, 2007, 2:49 pm
 TFP Expert

Joined: March 28th, 2007, 2:40 pm
Posts: 8082
Location: San Rafael, CA USA
MarkS at the Pool Forum posted this link that gives evaporation rates in different areas of the country. These are annual rates so the rate in summer is likely to be much higher than that in winter, but at least it's something -- it seems that the Class A evaporation values are for May through October so perhaps this is closer to a summer season rate. It should be noted that the evaporation for water in a swimming pool will probably be less than the pan evaporation rate since the pan rate is high due to the metal pan getting hot from the sun. This is why the evaporation rate for lakes is about 75% of the pan evaporation rate. On the other hand, pool water is typically heated and may be warmer than air temperature or certainly warmer than it would be if kept in a pan for 24 hours a day. So maybe the pool evaporation rate is close to the pan evaporation rate.

Post subject:
Posted: May 24th, 2007, 3:10 pm

Joined: March 29th, 2007, 8:36 pm
Posts: 274
Location: SE Louisiana
chem geek wrote:
MarkS at the Pool Forum posted this link that gives evaporation rates in different areas of the country. These are annual rates so the rate in summer is likely to be much higher than that in winter, but at least it's something -- it seems that the Class A evaporation values are for May through October so perhaps this is closer to a summer season rate. It should be noted that the evaporation for water in a swimming pool will probably be less than the pan evaporation rate since the pan rate is high due to the metal pan getting hot from the sun. This is why the evaporation rate for lakes is about 75% of the pan evaporation rate. On the other hand, pool water is typically heated and may be warmer than air temperature or certainly warmer than it would be if kept in a pan for 24 hours a day. So maybe the pool evaporation rate is close to the pan evaporation rate.

Interesting information, Richard. I'll bet that in my area of the country (Gulf Coast) the rate doesn't vary much from Summer to Winter as the temperature and humidity tend to track together (e.g. cooler but drier air in the Winter vs. warmer, wetter air in the Summer).

That site also makes it easy for me to convert the water level drop in my neagtive edge trough to the equivalent water levl drop in the pool. Thanks.

Post subject:
Posted: July 18th, 2007, 9:11 pm

Joined: May 27th, 2007, 10:16 pm
Posts: 205
Location: Fayetteville, Arkansas
In NW Arkansas with temps in the low 90's and humidity off the chart - I'm losing about half to three-quarters of an inch a day
in a 30,000 gal.

Post subject:
Posted: July 20th, 2007, 3:37 am

Joined: June 26th, 2007, 11:44 am
Posts: 68
Once when we lived in another house I had deer that would come and drink pool water, and for a good while, I was chalking it up to evaporation.

If it doesn't rain (and give me more metal free water YAY) soon I am going to have to add more water, we are down about 2 1/2 inches this week with over 90 weather, and lower humidity and a good bit of wind. I only have 6000 or so gallons though. No deer, but I did have a couple of horses from down the road in the yard this AM...

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 8 posts ]

 All times are UTC - 6 hours [ DST ]

#### Who is online

Users browsing this forum: No registered users and 0 guests

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

 Jump to:  Select a forum ------------------ News and Announcements    About Trouble Free Pool    Pool Rules    Become a TFP Supporter Swimming Pool Care    Just Getting Started    The TFPC method    Testing and Balancing Your Water    Algae - Prevention and Treatment    Spas and Hot Tubs    Chemistry 201    Swimming Pool Start-up and Closing    Baquacil - Use and Conversion    The Deep End... Equipment - Build, Use, and Repair    Under Construction    Pumping Station    Pool Cleaners    Above Ground Pools    Salt Water Chlorine Generators (SWG)    Chemical Automation and The Liquidator    Everything Else    Reviews - Equipment, Products and Builders    Backyard Oasis    Outdoor Kitchens & BBQ Islands The Skimmer Basket: The catch-all for any topics not covered above    Introduce Yourself    The Coffee Bar    Outdoor Cooking    Show off your Swimming Pool / Spa / Backyard Kitchen    Agree to Disagree    Forum Issues    Test Track    Suggestion Box