Pool evaporation rate?

[RocketDog]

Looking for info on typical evaporation rates for pools around Thailand. 

 

I don't think my pool is leaking but not sure. Recently I've been losing ~4mm/day on the pool fully exposed to sun and wind. 

 

The loss rate seems to correlate to hot weather and high wind, but I just starting keeping records a few weeks ago. 

 

Please list daily water loss and general conditions and any other helpful info. 

 

Ancillary questions:

Any experience or knowledge of automatic water makeup mechanisms to maintain water level?

 

Any experience or knowledge of pool overflow mechanisms to maintain water level in heavy rain season?

 

Thanks in advance for help or suggestions or experiences. Anything helps. 

[Crossy]

I don't measure ours, just top it up when it seems low.

 

You could try the bucket test.

• Get a bucket and put a mark about 1" down from the top.
• Fill it with pool water to the mark.
• Mark your pool level.
• Leave the bucket by the pool for 24 hours.
• If bucket and pool have lost the same amount, you have no problem.

[Excel]

Quite simple to calculate actually:-

https://www.engineeringtoolbox.com/evaporation-water-surface-d_690.html

[owl sees all]

On a really hot day a pond can lose one cm in 24 hours.

 

Swimming pools must be similar one would think.

[Excel]

1 hour ago, owl sees all said:

On a really hot day a pond can lose one cm in 24 hours.

 

Swimming pools must be similar one would think.

As I quoted in my post it can be determined almost exactly. As for your pond losing 1 cm then that is quite feasible for here. My pond requires on average 4600 litres daily to maintain its level which is in line of the calculations within my earlier post. That's a yearly daily average by the way

[Cake Monster]

Your Pool will lose more Water on Windy Days, as the Wind causes an effect called Evaporative Cooling 

[owl sees all]

1 hour ago, Cake Monster said:

Your Pool will lose more Water on Windy Days, as the Wind causes an effect called Evaporative Cooling 

I'm near a large salt farm and I'm often over there.

 

They (the salt farmers) tell me that March and April (before the rains come) are the best for evaporation due to the extreme heat.

[Bagwain]

Typical 1 finger p/day! Aproxx 1 cm! Winter a tad more! 

 

[scorecard]

7 hours ago, RocketDog said:

Looking for info on typical evaporation rates for pools around Thailand. 

 

I don't think my pool is leaking but not sure. Recently I've been losing ~4mm/day on the pool fully exposed to sun and wind. 

 

The loss rate seems to correlate to hot weather and high wind, but I just starting keeping records a few weeks ago. 

 

Please list daily water loss and general conditions and any other helpful info. 

 

Ancillary questions:

Any experience or knowledge of automatic water makeup mechanisms to maintain water level?

 

Any experience or knowledge of pool overflow mechanisms to maintain water level in heavy rain season?

 

Thanks in advance for help or suggestions or experiences. Anything helps. 

Pool supplies companies generally have a dye that you put in the water and it quickly highlights where there's any outflow happening. 

[Susco]

6 hours ago, Crossy said:

I don't measure ours, just top it up when it seems low.

 

You could try the bucket test.

• Get a bucket and put a mark about 1" down from the top.
• Fill it with pool water to the mark.
• Mark your pool level.
• Leave the bucket by the pool for 24 hours.
• If bucket and pool have lost the same amount, you have no problem.

 

The correct way would be to put the bucket inside the pool, if needed use a platform, so the top of the bucket is above water level.

 

Then fill the bucket to the same level as the surrounding water.

[daveAustin]

Yep, bucket typically goes on a step where it would be similar to temp of pool water. 

 

But mm is normal, nothing to worry about. Give us a shout when you're losing inches. ???? 

[Crossy]

Yeah on the bucket positioning, I was going for the easy version which would still show if the pool was losing massive amounts (and the bucket would probably lose more if it got warm/was higher up in the breeze).

 

[Susco]

On 2/27/2021 at 4:09 PM, Cake Monster said:

Your Pool will lose more Water on Windy Days, as the Wind causes an effect called Evaporative Cooling 

 

Yes I noticed that also. 1 month ago when it was much cooler than now,  but also more windy, my pool would lose more water than in the current climate.

[Cake Monster]

22 hours ago, Susco said:

 

Yes I noticed that also. 1 month ago when it was much cooler than now,  but also more windy, my pool would lose more water than in the current climate.

Evaporative cooling is when the wind blows , it causes a slight ripple on the surface of the Pool.

Because of this, there is a slight current created, where cooler water from the bottom comes to the top, and evaporates quicker.

Also due to the ripple, the actual surface area of the water increases, again giving more evaporation.

 

[Led Lolly Yellow Lolly]

I never measured accurately so I'm just throwing around wild figures about evaporation, but our commercial pool (around 300,000 litres not including surge tank) is topped up constantly with a ball valve in the surge tank. It runs constantly, we probably lose thousands of litres a day due to evaporation, maybe tens of thousands in certain conditions. As we pump our own bore hole water and carbon filter it, these costs add up annually, but there's not much you can do about it. Pools cost work and money.

[daveAustin]

^^ That's quite large. Evaporation aside, ball valves running all the time would points to a leak(s).

[SantiSuk]

My 4.5m x 15m pool, exposed to full sun and containing 90,000 litres (including reserve/overflow tank) loses about 7cm of water in the reserve tank each day during hot season (say March to August). This equates to 0.5% (one 200th) of the pool+reserve volume. During cooler climes this drops to about 4cm. Pumping is on 6.5 to 7 hours a day.

[Saanim]

Quote

 

Any experience or knowledge of automatic water makeup mechanisms to maintain water level?

 

The simplest way is a toilet valve mechanism installed in the OF tank.  I do not have it (it's not always very secure), rather looking inside every few days (having an easy view in), then if seeing the water is nearing to minimum, adding some water into pool, hence, the water in tank will rise as well.

     

In any case a precaution should be regarded against pump dry run.  A simple way is a swimmer switch that interrupts power incomer to the pump when the water level in the tank comes close  to the pump suction.

 

Quote

Any experience or knowledge of pool overflow mechanisms to maintain water level in heavy rain season?

If speaking about a pool with OF, it's always better to keep the water in the OF tank at its minimum level (as spoken above). Hence, we will have enough space for the water that comes with the rain, having so the water free of charge (with a low pH). 

 

Of course, while a heavy rain, the level in the tank will rise very high, in the ratio of the areas pool/tank.  I.e.  when pool is 4mx12m = 48m² and the tank is 1.5mx1.5m= 2.25m², the ratio is 21, with 5 cm of rain we get the water in tank by 1m higher.  Then, it is to think on a natural outlet into outside area. If not possible, another swimmer switch to install that will start an auxiliary small pump when the tank is full. It can be a small submersible pump that is needed anyway, when cleaning the tank after some time.

      

[Bagwain]

On 3/5/2021 at 6:53 PM, Led Lolly Yellow Lolly said:

I never measured accurately so I'm just throwing around wild figures about evaporation, but our commercial pool (around 300,000 litres not including surge tank) is topped up constantly with a ball valve in the surge tank. It runs constantly, we probably lose thousands of litres a day due to evaporation, maybe tens of thousands in certain conditions. As we pump our own bore hole water and carbon filter it, these costs add up annually, but there's not much you can do about it. Pools cost work and money.

As Dave Austin stated - you most likely have a leak if the ball valve is constantly runing. Or it is not position at the right level in the tank. 

 

To check you need to turn the supply off and see how far it drops. This will identify if there is a leak!

 

[Led Lolly Yellow Lolly]

No it's evaporation. This is a large pool, circumference is 60 or 70 metres, the evaporative losses are huge. We did all the leak tests, there is no leak. Right now there is so much rain, the ball valve is off, the rain out paces the evaporation. High humidity also slows the evaporation rate.

 

 

 

 

[Bagwain]

18 hours ago, Led Lolly Yellow Lolly said:

No it's evaporation. This is a large pool, circumference is 60 or 70 metres, the evaporative losses are huge. We did all the leak tests, there is no leak. Right now there is so much rain, the ball valve is off, the rain out paces the evaporation. High humidity also slows the evaporation rate.

 

 

 

 

So it must have a sizable shallow area? This would also increase the evaporation rate.

I would also guess that the surge/balance tank is undersised as well. Nearly 70/80% of the renos I have done, the tanks are undersized! The correct size is 10 % the size of the pool with a 7% amount of the pool water capacity. This will allow for the correct hydraulic balance & flow!

[Led Lolly Yellow Lolly]

You guessed wrong.

How does pool depth change evaporation rate? This is surely a surface area factor. Sincere question.

[Saanim]

2 hours ago, Bagwain said:

Nearly 70/80% of the renos I have done, the tanks are undersized! The correct size is 10 % the size of the pool with a 7% amount of the pool water capacity. This will allow for the correct hydraulic balance & flow!

Not sure what was meant with "size of the pool", the area or volume? Mostly I read an "advice" of the volume what's however wrong. A pool 5m deep will have the overflowing water same as a pool of 1.20m depth.  Meant is an OF water while swimming or coming from a heavy rain.

 

Actually, the OF from swimming is not so huge. It is 100 l of your body weight + some 100 l of waves. I have been watching the OF (whilst having an easy view into the tank adjacent to the pool). I almost do not see any much difference in the water level during 1 -2 people swim, especially when the pump is currently sucking and bringing the water back into pool. 

 

So, why to oversize the tank? What for? I run with tank water on its almost minimum level to keep the space for a rainwater to get the water free (for a later bottom sucking, backwashing). And when there is too much rain the water will go out from the tank into garden.   

 

Of course, unless I do not bring an elephant or two to swim...

 

[Bagwain]

2 hours ago, Saanim said:

Not sure what was meant with "size of the pool", the area or volume? Mostly I read an "advice" of the volume what's however wrong. A pool 5m deep will have the overflowing water same as a pool of 1.20m depth.  Meant is an OF water while swimming or coming from a heavy rain.

 

Actually, the OF from swimming is not so huge. It is 100 l of your body weight + some 100 l of waves. I have been watching the OF (whilst having an easy view into the tank adjacent to the pool). I almost do not see any much difference in the water level during 1 -2 people swim, especially when the pump is currently sucking and bringing the water back into pool. 

 

So, why to oversize the tank? What for? I run with tank water on its almost minimum level to keep the space for a rainwater to get the water free (for a later bottom sucking, backwashing). And when there is too much rain the water will go out from the tank into garden.   

 

Of course, unless I do not bring an elephant or two to swim...

 

What I quoted was the correct measurements for an overflow tank to work correctly given the right pump & filter size! Other than that you have issues. Which I see many times. But this is Thailand!

[Sydebolle]

 

No worries, 4mm within 24 hours during this time of the year with blazing sun and no rain in sight? Go to the fridge and get a cold beer! 

 

[jomtienisgood]

On 2/27/2021 at 7:56 PM, Bagwain said:

Typical 1 finger p/day! Aproxx 1 cm! Winter a tad more! 

 

Very unlikely as in winter the water will be frozen. 55555 ????

[TPI]

In Oz we allowed 12mm per day no matter how large the storage or how deep! It adds up to a lot of water...that's why we have "pool covers"!

[jomtienisgood]

27 minutes ago, TPI said:

In Oz we allowed 12mm per day no matter how large the storage or how deep! It adds up to a lot of water...that's why we have "pool covers"!

And beer - condoms.????????????

[Speedhump]

On 2/27/2021 at 8:20 PM, scorecard said:

Pool supplies companies generally have a dye that you put in the water and it quickly highlights where there's any outflow happening. 

I didn't know that. Thanks ????????

[aonangkrabi]

The evaporation varies from 2 mm/day on a cloudy day to 6 mm/day on a sunny day with wind. Source meteoblue.com.