Evaporation rate in pool

[Roehrle]

I have a 16x32 17,000 gal pool. In the summer I can drop up to 0.3" of water a day. This amount can vary depending on the air temperatures and humidity.I had water in the pool all winter so I don't think I have a leak. Anybody experiencing this amount from evaporation??

[chem geek]

The evaporation rate will vary depending on where you live as you can see in this map that shows annual evaporation rates in inches. In areas that have a cool/cold winter, the evaporation is mostly in the summer so you roughly double the rate as shown. So say that this is 50" per year on the map so double that for 100", divide by 365 and you get 0.27" per day. This is about what you are seeing and is probably normal.

Use of a pool cover will virtually eliminate this evaporation. By the way, the evaporation will often cause a rise in TA and CH over time since whatever TA and CH are in your fill water will get added to the pool. Evaporation only removes water from the pool, not other chemicals, so evaporation concentrates what is already in the pool, fill water dilutes it back to where it started PLUS adds whatever is in the fill water.

Richard

[Pool User]

Wow! Evaporation on the East Coast is way lower than I would have thought. Only 60" for Fl - amazing!

[chem geek]

The evaporation rate isn't as high as you would think in Florida because despite the high temperatures, the relative humidity is also usually quite high. I lived in Boca Raton for a year and can attest to the 90ºF with 95% humidity weather (it was hottest in August and most humid in September). Winter was much more pleasant. Evaporation rates get to zero when the humidity gets to 100% because the air is then already saturated with water. The fastest evaporation rates are in areas with very low humidity and high temperatures which is typically desert areas. Areas with a lot of wind also have higher evaporation rates.

[AlanGMyerson]

Evaporation rates get to zero when the humidity gets to 100% because the air is then already saturated with water.

Except for when the pool is heated. If the water is warmer than the ambient air, you will get a layer of warm air above the pool and this will allow evaporation.

[chem geek]

Good point. Thanks for catching that.

[Cappy]

Some observations resulting from my belief I had a pool leak!
I have an in-ground fiberglass sports pool in central Florida that is 24 feet long and 16 feet wide. At one end is a jacuzzi, the top of which is approximately four feet above the pool deck level, with a waterfall lip into the pool. A pair of 3-way valves at the pump allows me to shift suction variably between the jacuzzi drain or the pool's skimmer and drains, and to shift return flow between the jacuzzi jets and the four pool inlets. The only control method to regulate suction between the skimmer and main drain in the pool for running the pool vacuum is by blocking one of the two holes at the bottom of the skimmer - not how I would have designed it! The pad with the Hayward pump and cartridge filter is approximately one foot higher than the pool inlets, and two feet below the jacuzzi inlets. Additionally there are two valves accessible at the jacuzzi, one to close off the jacuzzi drain line back to the pump, and one to close off the inlets to the jacuzzi from the pump. I found the drain valve closed, inlet valve open, and leave them that way.

The previous occupant had drained it (as for why, let's not even get into that crazy mess except to say that divorce situations can make some people behave insanely!) and it was an algae dump when I arrived. After fully draining, pressure washing and refilling the pool, I thought I may have a leak as the water level was dropping as much as 1 1/2 inches or slightly more in a week, higher than I would expected from estimating evaporative loss alone. The pool is not being used as it is winter and it is unheated - brrrrrr - so splash out is not a factor! My first suspicion was a possible leak on the suction side of the filter system, since I am seeing some slight air bubbling on the two inlets closest to the pump, though none at all on the other two farthest from it. I also noted that if the 3-way return valve is left partially or more open to the jacuzzi inlets, within an hour or two of the pump stopping, the water level in the jacuzzi drops to the level of the inlets - I surmised this is caused by backflow of the higher level jacuzzi water through the system to the pool inlets, and does not occur if I close the line to the jacuzzi inlets. One possible leak source seemingly eliminated?

My next testing involved running the system for one week without any feed to the jacuzzi, returning filtered water to the pool only. Water level drop was right about 3/4 of an inch. The next week, I ran the system with full return to jacuzzi only for max waterfall flow. Water level drop was just over 1 1/2 inches. This leads me to believe that either the waterfall causes a significant rise in evaporative losses, or I may haver a leak underground in the return lines to the jacuzzi.

Anyone with experience in waterfalls and their effect on evaporative losses out there care to comment on this?

[John75]

Hi Miles! Have you checked this guide to swimming pool pumps at www.indoorpoolguide.com/filtration-systems

[yes9900]

Leak Detection Service - Look, I learned a long time ago with my swimming pool, that when I think there is something wrong with it there is. And I'm the type that wont rest until It's solved. So when I had similar problem as this title poster I decided to take action.

It was spring/summer and I was filling the swimming pool up every day. Sure we were using it, but it just felt excessive. But I wanted to be certain. I did some research of my own. I found that it is not uncommon for a swimming pool to lose up to .5" per day. Here in the Sacramento area I did the math and found that we loose .25-.65:'s all year long. So being that I thought I was loosing more water than I should I found a Sacramento pool leak detection company Dynamic Services that does a swimming pool leak inspection service. I gave these guys a call.

All my years of speculating were now answered. And I even paid a little bit more to find that I had 3 leaks in the light nitch and two in the main drain WTF. He even had me listen to the slow stream of water leaving the pool through the left drain. So with their paid service they patched most leaks for free with this super sealant stuff in a tube (some water tight space age stuff). Nonetheless they guarantee their work and its off my mind officially. So here's their number if you're in Sacramento (916) 532-7034 - Pool Service Sacramento or look up your local leak specialists, they can refer you. Just my 2$

(916) 532-7034 - http://h20freedom.com/ - Sacramento Pool Service

[Gary]

Sacramento Ca has some HOT temperatures. When the heat rises to a temperature 95 plus the homeowner often notices an increase in the normal summer evaporation rate. Add to this an afternoon breeze and an increase will be dramatic. New pool owners can have a difficult time determining what should or should not be evaporation. A bucket test will always prove to be accurate and is widely recommended among professionals. Go to http://www.leakdetectives.biz to learn how to perform a simple bucket test.