I have pool and I am not 100% sure if the filtration system has an underground leak on the suction side or I am just losing lots of water to evaporation.
I can do a bunch of tests with switching the pump off and measuring water level and other stuff to track down the leak if it is there but I’d like to do a ball park estimation of evaporation rates.
I know water temperature, surface area (although loss rate scales with area so that’s not too important) , I can get the daily air temperature and sunlight hours and possibly cloud cover and average wind speed from a weather website so could ball park a direct sunlight profile and use wind speed approximations as obviously the wind speed is not what the pool would actually see.
. Does anyone know the formula to get expected evaporation rates based on those ( or other factors)?
I am sure there are lots of other things I could do to track down the leak if there is one, but I am specifically interested in calculating theoretical evaporation.
FWIW I am also playing around with matlab trying to pull in data from the web and plot water loss against weather and modeled loss rates but that’s just a side project .
Don’t bother with any of that.
Take some dye (I used the handy red Ph indicator bottle), and gently squirt some near each return, after the pool has been off for awhile. If the dye gets sucked into the return nozzle, you have a leak. You can also do this in the skimmer basket. The main drain is harder, although you could dive down and do it.
One factor which you haven’t mentioned but which would be important for calculating theoretical evaporation rates would be the amount of water vapor in the air, i.e., relative humidity. If there’s already a lot of humidity in the air, the water in the pool will not evaporate as fast.
(I’m not sure how you would actually calculate this effect, but I’m pretty confident that it would make a difference.)
I’ve been looking into the exact same thing. I saw a comparison of different evaporation models that got wildly different numbers. I’m going to use the water level measurement method (measure water drop in the pool compared to water drop in a nearby bucket) once we get a stretch without rain. Probably measure overnight so solar heating of the sides of the bucket doesn’t influence the measurement.
ETA are you ruling out underground leaks on the pressure side?
Good thought.
I wonder if putting the bucket in the pool on the steps so the lip of the bucket is above the water level of the pool would be better
That way both the bucket and the pool are in the same conditions, but the bucket is isolated from any potential pump leaks. Also you could run the experiment in the day with max evaporation, over night there may not be enough evaporation that you cant get a precise enough measurement and have limit of detection issues.
Mike’s, good point on humidity I’ll drag that into my side project .
Still interested if anyone knows any ballpark equations for solar evaporation rates.
I dont think I have leaks on the return side , I would think I would see entrained air on the return nozzels on start up but the system seems to hold fluids when shut down .
Surface pump and filter lines are all dry, I suspect if if have a leak it is on the suction side in the burried line from the skimmer/sump to the pump .
I like the idea of the bucket in the pool, I’ll try that. This time of year the pool is in frequent use during the day, so I have to run it at night. Still significant evaporation here in the desert overnight, but since I am looking to cancel out evaporation the less the better.
I am haveing the same question, only mine is with a fountain with a “swimming pond”. the level goes down more than I think it should when running. I have purchased a TDS (total desolved solids) meter. I plan on filling it to the full mark and start the pumps to circculate the water. I will take a reading. Then over the next week each day take readings after the pump runs. If the water level drops and the TDS does not increase or only increases a little then I have leak. If the TDS increases as the llevel goes down then it is evaporation.