Water evaporation

BarryH

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After many years with fancy goldfish I have started setting up a 60cm tank without a lid, just the light above.

What has really surprised me is the amount of water lost to evaporation. Never had to top up a a goldfish tank before but they all have covers on them.
 

dw1305

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Hi all,
What has really surprised me is the amount of water lost to evaporation. Never had to top up a a goldfish tank before but they all have covers on them.
A lot of it is the heater in a tropical tank, it means the water is warmer than the room and more evaporation occurs.

cheers Darrel
 

MJQMJQ

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11 Nov 2019
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SIngapore
After many years with fancy goldfish I have started setting up a 60cm tank without a lid, just the light above.

What has really surprised me is the amount of water lost to evaporation. Never had to top up a a goldfish tank before but they all have covers on them.
Same here,smaller tanks or tanks with more surface area lose water to evaporation more quickly.I lose abt 1-2 litres per week from my 32 litre tank but luckily my tap water TDS ia about 150-200.Watch yr TDS though :)
 

BarryH

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Same here,smaller tanks or tanks with more surface area lose water to evaporation more quickly.I lose abt 1-2 litres per week from my 32 litre tank but luckily my tap water TDS ia about 150-200.Watch yr TDS though :)
WOW! I'd never have guessed at that much. First open topped tank and I'm really surprised.
 

dw1305

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Hi all,
Relative humidity plays a part too!
It does, if the air is fully saturated with water vapour, you don't get any evaporation.

In Singapore I assume it is always hot and humid, but this is quite important for us in the winter.

In the UK the atmosphere is pretty wet in the winter, but the air is relatively cool. When the 100% RH air comes into the house it warms and the relative humidity falls. This allows it to pick up water from the fish tank etc. but when it reaches a cool surface (usually a window) the air cools and the water condenses.

If you live somewhere where the air is cooler and drier, you have even more of a difference.

The relationship between water content, temperature and relative humidity <"is non-linear">, but near enough to say that warm air can hold a lot more water than cold air.

rh3.png

cheers Darrel
 
Last edited:

MJQMJQ

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Hi all, It does, if the air is fully saturated with water vapour, you don't get any evaporation.

In Singapore I assume it is always hot and humid, but this is quite important for us in the winter.

In the UK the atmosphere is pretty wet in the winter, but the air is relatively cool. When the 100% RH air comes into the house it warms and the relative humidity falls. This allows it to pick up water from the fish tank etc. but when it reaches a cool surface (usually a window) the air cools and the water condenses.

If you live somewhere where the air is cooler and drier, you have even more of a difference.

The relationship between water content, temperature and relative humidity <"is non-linear">, but near enough to say that warm air can hold a lot more water than cold air.

rh3.png

cheers Darrel
Now I get around 1 litre loss per week cos its wet season during dry season 1.5-2.Was thinking of getting a cover but the condensation will look ugly.
 

zozo

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And the draft in the house does a lot. :) I loose between 2 and 3 litres per day over 2 open-top tanks. And the average humidity in the house is +/- 40%. But its an old drafty house build in 1920.

In the winter its a 20°C tank temp and max 18.5°C room temp. Doesn't make much of a difference in volume that evaporates.
 

MJQMJQ

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And the draft in the house does a lot. :) I loose between 2 and 3 litres per day over 2 open-top tanks. And the average humidity in the house is +/- 40%. But its an old drafty house build in 1920.

In the winter its a 20°C tank temp and max 18.5°C room temp. Doesn't make much of a difference in volume that evaporates.
Yep the draft removes moisture laden air.
People produce on average 1.2 litres of water through perspiration per day.
@zozo this is what u need.A human humidifier.But on a side note that much perspiration?At what temperature? :)
 

becks

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Only knew that because humidity in dwellings is something I’ve been learning a lot about recently :)
 

ian_m

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Eastleigh
Slight off topic, if you have damp issues in your house, I would highly recommend these.
https://www.dehumidifiersuk.com/dio-ruby-dry-dh600-dessicant-dehumidifier-5-5-litre-extraction.html

They do not use a compressor so are virtually silent, so can be installed in living spaces without keeping you awake at night. Also work down to 0'C (unlike compressor dehumidifiers) so can be used in outside sheds/garages etc.

My mate had severe issues with damp in his house, basically caused by humid air from tiny kitchen passing through his lounge and up the stair case, which enters into the lounge, and condensing as water on upstairs windows. Tried a curtain round the stairs in the lounge, did work well stopping the moisture but looked naff and was always not "closed". Installed one of these dehumidifiers on upstairs landing. It only lasted a day before it stopped as water compartment was full !!!. Ended up plumbing it in so water continuously drained to outside gutter. Moisture issue was eventually 100% solved (and dehumidifier sold) due to kitchen extension moving the cooker further away from the door along with decent extractor cooker hood, preventing moisture getting out in the first place and replacement double glazing upstairs all with trickle vents.
 

becks

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8 Jul 2018
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England
I think a better alternative to a dehumidifier is installing PIV, something like Naurie drimaster. People are concerned about pushing cold air from the loft space into the house and believing it’s going to make the house cold. They are great and drier air is cheaper to warm up than humid air.

the drimaster is about 18w irc, they do one with a heated element, but I would not really use one.
 

BarryH

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25 Feb 2017
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Derbyshire
Back on the water evaporation again, has anyone made glass or clear plastic covers for their open topped tanks?
 

Simon Cole

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25 Dec 2018
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Buckingham
I prefer glass sheet to plastic. It will not scratch or discolor and can be cleaned quickly with distilled vinegar. Snails will also find the underside quite appealing, and the top makes a nice place to put a cup pf tea.
 

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