# How Fast does your pool water evaporate ???

#### beez74

##### Well-known member
About how fast does your pool water evaporate in the summer??? I'm in AZ and trying to determine the increase in my water bill since its gotten hot outside....... gallons by numbers??? \$ amount of water bill increase???

#### mknauss

TFP Expert
Bronze Supporter
In Laughlin I lose 3/4" to 1" per day from mid - May to mid- October.

#### JoyfulNoise

TFP Expert
Platinum Supporter
You don’t say where you are in the Phoenix metro area but in the month of July, based on historical Pan evaporation data, you lose about 13” of water in the month of July. If you know your pools surface area, then you can calculate the gallons of water used -

100 cubic feet = 748 gallons

#### JoyfulNoise

TFP Expert
Platinum Supporter
So, for example, Tucson averages about 13” of water loss per month in Jun/Jul/Aug. My pool is 468 sq ft.

468 x (13 / 12) = 507 cu ft = 5 CCF

So my pool will use about 5CCF of water per month.

#### beez74

##### Well-known member
Buckeye area ....my pool is 13500...was trying to determine what was doing the most damage to my water bill, my pool or the irrigation system.

#### mknauss

TFP Expert
Bronze Supporter
Depending on your landscaping, most likely the irrigation system.

#### JoyfulNoise

TFP Expert
Platinum Supporter
Irrigation systems tend to develop leaks and weeping valves. I routinely have to repair mine about a dozen times a year. Irrigation can also add a few CCF per month.

#### duraleigh

TFP Expert
Platinum Supporter
In The Industry
So, mknauss, with Phoenix averaging somewhere around 13" of evaporation, Tucson and Vegas about the same, you seem to be about 25" plus.......around double that average. I think you have a leak!

#### mknauss

TFP Expert
Bronze Supporter

We are at 400' above sea level and 10+ degrees warmer than Phoenix. We are at a cool 110F today. A bit below average. Single digit humidity.

#### MyAZPool

Gold Supporter
beez74
I'm down the road in Chandler. Just to add to the conversation and to keep you from falling over when you compute and learn your pool's water usage in the summer.
The total surface area of my pool and spa is 678 square feet.

For the 19 days of July, my pool has used 7,193 liters or 1900 gallons, all due to evaporation (no backwash's this month).
Yep, that's about 100 gallons or 13 cubic feet of water per day.

That is about normal for me during the summer months. In the fall it will decrease to approximately 60 gallons a day etc.
So don't be too surprised.
r.

#### JoyfulNoise

TFP Expert
Platinum Supporter
beez74
I'm down the road in Chandler. Just to add to the conversation and to keep you from falling over when you compute and learn your pool's water usage in the summer.
The total surface area of my pool and spa is 678 square feet.

For the 19 days of July, my pool has used 7,193 liters or 1900 gallons, all due to evaporation (no backwash's this month).
Yep, that's about 100 gallons or 13 cubic feet of water per day.

That is about normal for me during the summer months. In the fall it will decrease to approximately 60 gallons a day etc.
So don't be too surprised.
r.
That works out to about 1/4” per day ... a bit on the low side for this time of year so good for you!!

#### MyAZPool

Gold Supporter
That works out to about 1/4” per day ... a bit on the low side for this time of year so good for you!!
Not sure if that has anything to do with some of the partial shade that the house and the palms provide or not. That would be hard for me to say. Any thoughts about pool shading having a positive effect on lessening evaporation of pool water?
Wow, I thought 100GPD was high. But I did confirm that number with some bucket tests that I performed last year and its right in the ballpark, so I'm pretty sure the water meter is accurate.
If you think that is a bit low for our area and the square footage of my pool, I like it.
Thanks Matt....
r.

#### JoyfulNoise

TFP Expert
Platinum Supporter
Not sure if that has anything to do with some of the partial shade that the house and the palms provide or not. That would be hard for me to say. Any thoughts about pool shading having a positive effect on lessening evaporation of pool water?
Wow, I thought 100GPD was high. But I did confirm that number with some bucket tests that I performed last year and its right in the ballpark, so I'm pretty sure the water meter is accurate.
If you think that is a bit low for our area and the square footage of my pool, I like it.
Thanks Matt....
r.

Don’t know how fancy your meter is but if you could track your water usage by hour and correlate that to outside air temperature minus the pool water temperature that would be interesting. You should see the water flow rate jump up when the temperatures invert - Tpool > Tair - and that should happen in overnight hours.

Seasonally, you should se increases in water flow into the pool during the Fall month’s when the evening temperatures drop considerably below the pool water temps. It’s not uncommon in the desert to see a 20F inversion in temperature which drives A LOT of evaporation.

#### MyAZPool

Gold Supporter

Don’t know how fancy your meter is but if you could track your water usage by hour and correlate that to outside air temperature minus the pool water temperature that would be interesting. You should see the water flow rate jump up when the temperatures invert - Tpool > Tair - and that should happen in overnight hours.

Seasonally, you should se increases in water flow into the pool during the Fall month’s when the evening temperatures drop considerably below the pool water temps. It’s not uncommon in the desert to see a 20F inversion in temperature which drives A LOT of evaporation.
Thanks. Yes, I do notice that the daily flow rate on the meter does increase when there is a larger diff between the air temp and the water temp. Last few days, Tpool has been high 80s and Tair around 110. I notice it tends to decrease just slightly when we experience our monsoon conditions.
Thanks again Matt...
r.

#### Arizonarob

Gold Supporter
Silver Supporter
TFP Guide
Between the pool and irrigation, my water use goes up 1k gallons a month for June, July, and August.

#### MyAZPool

Gold Supporter
Between the pool and irrigation, my water use goes up 1k gallons a month for June, July, and August.
Rob,
Only 33 gallons per day loss to evap and including irrigation? Wow, that's fantastic. How are you doing that? Are you using a cover? What is your pools square footage?
I need your "secret". If you give it to me, I promise "Free Beer". Really
r.

#### JoyfulNoise

TFP Expert
Platinum Supporter
Rob,
Only 33 gallons per day loss to evap and including irrigation? Wow, that's fantastic. How are you doing that? Are you using a cover? What is your pools square footage?
I need your "secret". If you give it to me, I promise "Free Beer". Really
r.
@Arizonarob fills his pool with jello ... very low water loss. But he doesn’t use any jello products with Red #5 dye in it because he knows those unnatural dyes are not good for him....he uses dyes extracted from CBD oil processing ...

TFP Expert
Bronze Supporter

MyAZPool

#### Arizonarob

Gold Supporter
Silver Supporter
TFP Guide
Rob,
Only 33 gallons per day loss to evap and including irrigation? Wow, that's fantastic. How are you doing that? Are you using a cover? What is your pools square footage?
I need your "secret". If you give it to me, I promise "Free Beer". Really
r.
I don’t have much for irrigation, and my pool is only 11k gallons. Plus I have a shade sail over my pool which helps some.
But also, that’s a 1k gallons more then I “normally “ use, so you have to factor that in too. My normal monthly usage is 5k gallons for just 2 people and a couple of fur balls I have to keep watered.

#### MyAZPool

Gold Supporter
Ah, okay. Well that explains some of the less than average water use I guess.
Not a super "secret" lol, but I still wouldn't mind buying you a brew one of these days.
And we can stay right here in Chandler and not have to drive to Area 51
r.