The amount of evaporation can vary greatly depending on the time of year, where you live, surface area of your pool, and the siting of your pool, just to name a few factors. You can search and (hopefully) find the pan evaporation rates for your area.

Pan evaporation is a measure of the amount of evaporation that might be expected from a water body. While it's often used for lakes and reservoirs, it still has significance to your pool. Some sources indicate that one should use only 75% of the listed pan evap rate as an indicator of true evaporation, due to the way pan evap is measured. For me, I don't need it to be that precise, just a general indication of how much my water level might decrease.

As an example, the average pan evaporation rates for my area of North Texas are 9.5" in May, 11.21" in June, 12.66" in July, 11.7" in August, and 8.78" in September. If you divide any of those rates by 4 or 5, you'll see about how much water I might lose to evaporation each week, assuming no added rainfall. (Even if you use just 75% of the readings, it's still quite a bit of water loss due to evaporation!)

The monthly pan evap rates for January and February in my area are 2.29" and 3.16" respectively.

You should be able to do a search for "bucket test" which will give you a quick and easy test to determine if you might have a leak.

Water features might increase water loss through evaporation and/or splash-out.

I sympathize...it's hard getting to know what's normal for your pool in that first year.

I live in Hawaii now and evaporation is not a problem (it rains too much). When I lived in Nevada it was not that unusual for a pool that is uncovered to lose an inch to an inch and a half of water a day during the summer time. I would suggest that you turn off all of your water features for a few days or so and see if there is any significant reduction in the amount of water you are losing. You could also set a bucket of water out by the pool, make a mark where the the water level is in it, and check how much water has evaporated out of the bucket after a few days and compare that evaporation level in comparison to the pools evaporation.

Hi,

I also had my pool finished in Nov, 07 timeframe. I Live in San Diego area and the pool is about 450 sq ft rectangle.I ran a bucket test from Dec 25 till Dec 31 and measured a loss of little over 1 inch in that time span. I would like to ping some San Diego natives to see if this is normal? Also, where can I find the Pan evaporation rate for city?

Thanks
--Scal

Scal...I found my rates in a water canal study the state was doing for my city. To know how much runoff the canal would have to handle, they had to know the precipitation amounts and how much would naturally evaporate in any given period of time.

A bi-monthly gardening magazine for Texas also lists the evap rates for various major cities in the state, along with the typical rainfall (or other precipitation)amounts.

Just some ideas on where to start looking...

I DO realize you're in CA...but maybe there's a gardening magazine for CA that has the same info??? Perhaps your city or state water board/dept/district has this info???

Here is a link to an evaporation map:

http://www.grow.arizona.edu/images/water/panevap.gif

It give you annual evaporation rates in iches. I know many people have reported that summertime evaporation rates can be double the rate given here, but it may give you some idea. As you can see the rates do vary quite a bit from one area to the next.

I agree the bucket test is the best indicator as to whether or not you have a leak.

Good luck.

riles

Thanks,

I am going to re-run the bucket test in a few days and compare the rates. The pool guy I talked to said that most pools leak some water. So, it is not abnormal to see the water level in the pool to be lower than the bucket(about 1 inch lower in 1 week does suggest a leak to me though). Assuming there is some leakage somewhere, what are the next steps in diagnosing the leak? I do see some effervescence on the coping slab just above the skimmer and on the slab that is next to the raised spa.

--Scal

I'm not sure I buy the "most pools leak some water" line. Pools can and should be made leak-free in my opinion.

riles

There is no way your pool should be leaking water unless you have a plumbing leak or something in the pool is not sealed properly. You said your pool has been checked for leaks and that none could be found, who checked it and how? Did they pressurize the plumbing or dive the pool to check for leaks around the light or skimmer or the main drain? There should be a leak detection company of some kind in your area that you could call to come out and find the leak, but if your pool has was finished in September your pool builder is responsible to handle it, not you. Two inches of water in a couple of days is a great deal of water loss.

Hi,

We found the source of our leak. As an after thought, we had decided to put in an auto fill. The Pool guy drilled a hole in Gunite and then pressure drilled through the dirt (underneath the Deck)to push the pipe through it. The pipe had a hairline crack and was leaking for about 6 weeks before it was fixed in the last few days. The fix involved abondoning the new line (and filling up the drilled hole in pool with Epxy).

Instead, we used the manual fill line to connect to the autofill apparatus. The manual fill line is only about an inch lower than the tile line in the pool. As a result, the water level in the pool is now 1 inch below the tile line. Before this change, the water level that we were maintaining was in the middle of the 6 " tile. Are there any consequences of having the water level only 1" below the tile line?

The pool builder did offer to move the line 2" lower. However, that would involve draining the pool a littel bit, knocking off some gunite, lowering the end of the manual line, by pittung some kind of an L junction, putting some concrete back and finishing with plaster as a last step. I thought I will get the experts opinion hebefore I made any decision.

Regards
--Scal

My first thought is: doesn't this put the water line below the mouth of your skimmer?
Second, you don't want the water level kept below the tile line. As beautiful as the tile in your pool probably is the practical reason for pool tile is that the scum line which will develop at water level is much easier to clean off of tile than plaster.
Would it be possible to drill a hole right below the coping for your manual fill line?
Good luck.

Tony

Tony,

One clarification. The water level is 1 inch below, from the top of the tile line. So, Skimmer operation is fine here.

--Scal

?? You might be able to use this?

http://www.ezautofill.com