Evaporation

[Gardian]

My French neighbour has just commissioned his swimming pool: it's been eight years in construction, but that's another story!

As you'd expect, it took a couple of days to fill and some of the grandchildren were around yesterday to 'christen' it. Anyway, this morning he asked me how much water we lost from our pool through overnight evaporation. "Overnight?!!" I said. I explained that I probably did lose a bit, maybe 1cm / day with the current heat, but the automatic refill took care of that and anyway, surely any loss through evaporation would be when the sun was on it, not overnight. If he's lost 1cm overnight (and for his size of pool, that's roughly 0.5m3, or 500 litres), then he's probably got a leak somewhere. 

He insists that he's read on the internet that that's the case. I told him that he's a mad Frenchman and so there's now a croissant and a pain au chocolat on the correct answer. Have I got to eat humble pie?   

[pachapapa]

Evaporation rates will vary greatly with relative humidity and wind, last night was humid with low evaporation rates, could be a leak.

Relative humidity can be easily measured using a psychrometer and psychrometric charts. In effect the dry bulb temperature and wet bulb temperature, the wet bulb temperature can be bodged by putting a cotton sleeve around the bulb of the thermometer and keeping the sleeve damp by placing the end in water. The ensuing evaporation will depress the temperature. In the South African Gold Mines for speed we used a whirling psychrometer, looked a bit lika a football rattle.[:)]

[Théière]

He he, well most of the evaporation will be during the day for sure, if it is warm enough overnight then there could be some but it's most likely a leak. His "evaporation" will stop when it gets to the lowest point of the leak, I just hope that it isn't the bonde de fond!

If the pool was constructed so long ago but the fittings were in place then some degradation may have occurred, all a bit supposition. Does he have a pool cover, put that on overnight and see if the water still lowers overnight.

[Chancer]

Wandering herds of elephant or migrating wilderbeest using it as a watering hole?

[Gardian]

[quote user="Chancer"]Wandering herds of elephant or migrating wilderbeest using it as a watering hole?[/quote]

[:-))][:-))][:-))]

Actually, not quite so daft, because the sanglier do wander down the lane at night to drink from the local stream. Mark you, there'd have to be about 500 of them!

[Gardian]

[quote user="pachapapa"]

Evaporation rates will vary greatly with relative humidity and wind, last night was humid with low evaporation rates, could be a leak.

Relative humidity can be easily measured using a psychrometer and psychrometric charts. In effect the dry bulb temperature and wet bulb temperature, the wet bulb temperature can be bodged by putting a cotton sleeve around the bulb of the thermometer and keeping the sleeve damp by placing the end in water. The ensuing evaporation will depress the temperature. In the South African Gold Mines for speed we used a whirling psychrometer, looked a bit lika a football rattle.[:)]

[/quote]

Oh blimey, I can see his eyes glazing over etc if I start talking about psychrometers.

[steve]

Easy way to find out - fill a bucket with water to the same level as the pool and place it on the steps (you know what i mean) - if its a leak, the bucket will have more water than thepool after a period of time, if its evaporation, levels will be the same

Steve

[Gardian]

[quote user="Théière"]

He he, well most of the evaporation will be during the day for sure, if it is warm enough overnight then there could be some but it's most likely a leak. His "evaporation" will stop when it gets to the lowest point of the leak, I just hope that it isn't the bonde de fond!

If the pool was constructed so long ago but the fittings were in place then some degradation may have occurred, all a bit supposition. Does he have a pool cover, put that on overnight and see if the water still lowers overnight.

[/quote]

Théière ...............

No, he doesn't have a pool cover yet. It's a sort-of figure of eight shape, with a jacuzzi on one side, so it's going to cost him a bomb when he does get round to having one made. I suspect that your theory of fittings degradation is the most likely cause.

The pool was finally rendered last weekend, using some kind of special coloured cement. He started filling the pool within 12 hrs of the rendering being completed - he reckons that it was "part of the process". Right from the start of the water going in, there were tiny bubbles erupting from all over the submerged render - didn't look healthy to me, but he thought it was OK. 

Gentlemen - thanks very much for your thoughts & suggestions. He's topped the pool back up now, but I suppose the answer is to monitor the 'evaporation' between (say) 08.00 - 20.00 & 20.00 - 08.00. That'll prove or disprove the nightime theory.    

[Gardian]

[quote user="steve"]Easy way to find out - fill a bucket with water to the same level as the pool and place it on the steps (you know what i mean) - if its a leak, the bucket will have more water than thepool after a period of time, if its evaporation, levels will be the same

Steve
[/quote]

Steve ..............

I knew that I'd read something like that before, but couldn't remember how it worked. That's great - I'm on the way with my clean bucket (his are all full of old cement & manky).  Thanks.

[Chancer]

That must be some leak if after one night there is more water in the bucket than the pool!

[pachapapa]

[quote user="steve"]Easy way to find out - fill a bucket with water to the same level as the pool and place it on the steps (you know what i mean) - if its a leak, the bucket will have more water than thepool after a period of time, if its evaporation, levels will be the same

Steve
[/quote]

Smart & Simple; I like it.[:)]

[krusty]

We also the used the football rattle , we called it a Whirling Hygrometer.

[Théière]

Well? how much water "evaporated" over night.

[pachapapa]

[quote user="krusty"]We also the used the football rattle , we called it a Whirling Hygrometer.[/quote]

The pubic hairs from an elephants gear work better than seaweed.[:)]

Sorry did I get the translation from Afrikaans wrong.[:D]

[Gardian]

[quote user="Théière"]Well? how much water "evaporated" over night.[/quote]

There was a new phenomenum known as reverse evaporation.  This was brought about by a bloody great thunderstorm at about 06.00 this morning.

Michel has gone off for the weekend, so I can't pursue my attempts to claim my croissant etc. More next week I expect.

[krusty]

Keep your hands off my gear pp[:P]..........I did a very short spell in SA in Jo-burgh at the steel works.

[Gardian]

Hmmm.   I just dropped by my neighbour's house to have a look at the water level.  If we assume that after yesterday' storm, the pool was pretty well full, then I reckon that it's dropped by about 12cms in (say) 36hrs.  It has been extremely hot today (40C in the shade at 15.30), but nonetheless you wouldn't get that sort of loss through evaporation, whether it was by day or by night! It makes our friendly squabble academic - he's got a serious leak & he's going to have kittens when he sees it.

I really feel for him: he's a lovely man, who would do anything for you. Many years ago he had an industrial accident which badly damaged his ankle and he has been unemployed ever since. Just a month ago he had what amounted to ankle replacement surgery and he's just out of plaster and about to start intensive physiotherapy. He's in no physical condition to mess around with the pool and fix the problem. His sons are willing and able, but have livings to earn and families to spend time with at the weekends.

Oh well, we'll see. Will still do the bucket test to prove the leak, but it's a racing certainty.

Will update on progress.  

 

[Théière]

Gardian that should have put the level well below the skimmer and possibly the returns so the leak is most likely from the bottom drain if he has one or round the roman end steps if fitted is a good place to start.

Using food dye poured around suspect areas you should see the dye being drawn into the leak. Otherwise the professionals have leak detection equipment and could survey it.

 

[Gardian]

Just dropped by to assess the mood. 

He's still convinced that it's evaporation & insists that he's only lost a couple of cms. I think not, but I'm staying out of it for the time being.

Thanks for the advice re leak detection - it'll be needed! The trouble is that he thinks that all Englishmen are idiots with no real understanding of ............... well, anything. We eat strange things, speak a strange language and have strange habits (like paying our taxes and not getting work done 'on the black'). Apart from that, he quite likes us.

[Chancer]

Those that can't contribute endlessly to a debate on terroir, i.e; Les rosbifs  are clearly cretins and anything they say on any other subject should be treated with scorn. 

[chirpy]

I WOULD NOT EXPEXT their would be any humidity in the steel works!![:P]well not near the funrace.....I guess you may have been checking cooler areas before painting.

[Théière]

I wonder just how the two countries ever managed to build Concord (the aircraft) not rapport [:)]

[Polly]

[quote user="Théière"]I wonder just how the two countries ever managed to build Concord (the aircraft) not rapport [:)][/quote]

Probably because the nice Brits agreed to the French spelling: Concorde

[Cendrillon]

Théière wrote:

I wonder just how the two countries ever managed to build Concord (the aircraft) not rapport

Probably

because the nice Brits agreed to the French spelling: Concorde

Did anyone see the programme about Concorde on channel 4 last night?

[steve]

dam, missed it & there was me who used to work in the wind tunnels that developed the wings! (well before my time though!)

Steve