Evaporation and Swimming Pools

Love them or hate them, there’s no denying that a pool cover can save massive amounts of water.

Just how much water they save depends on a number of factors (such as the pool surface area, the amount of wind, shade, and water/air temperatures). Anywhere between 2mm and 10mm of water every day is seen as an acceptable water loss – but this all adds up – and without rain or top-ups, a pool can easily lose its entire volume of water – every year!

The single most effective thing a pool owner can do to save water is to buy (and use) a pool cover. To be honest, it doesn’t even have to be a proper pool cover – any sort of covering will help prevent evaporation – it’s just that a pool cover will be more effective, will last longer, and will be easier to use than say – cling wrap or builders plastic.

So how does it work? It’s all about evaporation. Evaporation happens when water turns into gas (such as steam, when you boil the kettle). Obviously, your pool is not boiling like a kettle, but the theory is the same. On a hot, sunny day, the water inside your pool gets warm – here in Queensland, even an unheated pool can reach temperatures over 30 degrees in Summer. Once the sun goes down and the air temperature drops to below that of the water, evaporation will occur.

Without a cover, that water vapour will release back into the atmosphere – but with a pool cover in place, it can’t escape and stays in your pool, where it belongs. (Going back to the boiling kettle analogy – if you look under the lid of your kettle after it’s boiled, you’ll see it’s covered in steam which has turned back into water droplets).

The majority of evaporation will occur in the evening and very early morning as the sun goes down and comes back out – so this is the most important time to use your pool cover if preventing evaporation is your main priority.

There are other ways to prevent water loss to evaporation – anything that reduces the amount of wind and sun on the pool’s surface will help, so things like a shade sail over the top, trees around the fence line – adjacent buildings – they’ll all contribute to reducing evaporation. The single best thing to do though, is use a pool cover. A mesh leaf and debris style pool cover (like a Pooltex or Leafstop) will stop around 50% of evaporation, and a solar cover such as the Oasis Solar Cover range will pretty much stop evaporation completely.

ABGAL Oasis Solar Pool Covers have been independently tested and proven to stop up to 99.84% of evaporation. They are Climate Care Certified, Smart Approved WaterMark Licensed, and Water Wise accredited, complying with water-saving standards across all drought-declared Australian states and territories.

Where on the pool should I position my reel?

If you’re putting a solar pool cover on for the first time, chances are, you’re also putting a reel (roller) together too. So where do you put it? Ideally you should make this decision before you install the cover, because some positions will require you to leave the cover slightly longer than others.

Don’t worry if you have already cut the cover to size. It’s not a big deal.

If you have a rectangle shaped pool, the standard approach is to place the reel at one end of the pool – slightly straddling the pool, so the blanket rolls easily on and off the tube without dragging across the coping. People normally put it to the far end, so its furthest away from where they will view it from.

The reel should sit at the end of the pool, hanging slightly over the edge, so that the cover does not drag over the pool coping when being rolled up.

This reduces wear and tear on your solar pool cover, and will help to get the best life expectancy from it. (Don’t forget to put the overcover on once it has been rolled up).

If you have an oval, kidney or other irregular shaped pool, the reel should be placed over the pool, at it’s widest point. When doing this, the blanket rolls from both directions, so it rolls faster and is easier to handle too.

When using this position, the blanket should be left a little longer in the length – if after attaching the extra length is not needed, you can trim it back then.

If your pool has a step, you can treat this as a separate piece, and simply fold it onto the main cover before rolling, enabling it to be rolled onto the roller. You can see in the image below how the step piece has just been flipped up onto the body of the cover, leaving it as a neat rectangle to roll up.

What is the thickest solar pool cover?

In Australia, we measure solar pool cover thicknesses by micron – and micron is just a measurement. A micron is very small – one-millionth of a metre in fact. To put it into real terms, a human hair is about 50 – 70 micron. In Australia, a 200-micron pool cover would be considered lightweight, and 610 is currently the heaviest that we are aware of. Anything over 610 would start to get very heavy and difficult to roll on and off of a pool.

At ABGAL, our thickest solar pool cover is 610 micron – Triple Cell. The next thickest and most popular selling solar cover is 550 micron from our Oasis Solar Cover range. Oasis 550 is available in Premium Blue, SilverBack and Clarity.

The benefit of heavier (thicker) solar covers is that they are more durable than a lighter cover, and will be more resistant to chemical damage and punctures.

Helping our Farmers – Our pledge!

We started our journey with Farm Angels back in 2019, when when they were known as “Drought Angels”, and we pledged to donate 40L of freshwater for every Oasis Solar Cover we sold.

Over the years the needs of Australian Farmers evolved, as did Drought Angels – pivoting from their primary focus of drought relief to include other disaster relief, such as bushfires, plagues and flood.

In July 2024 Drought Angels rebranded as Farm Angels, and while our pledge of 40L for every Oasis Solar cover remains the same, it no longer ends up with the farmer as 40L of water. Sometimes its stock feed or petrol – sometimes its a pre-paid visa card so they can pay a bill. We donate the financial equivalent, and Drought Angels passes that onto an Aussie farmer in need, in whatever format they need.

Drought Angels are here to provide support for our Aussie Farmers, and we in turn, continue to support them with our pledge of the cash equivalent of 40L, for every Oasis Pool Cover sold.

Based on the front line in Chinchilla, in Queensland’s Western Downs, Farm Angels are in direct contact with those who are most in need and are able to distribute whatever aid is needed to those who need it most.

As of August, 2024, thanks to people like you, we have been able to donate the financial equivalent of more than 1000,000 litres to Farm Angels, in support of Aussie Farmers. If you would like to make your own donation to Farm Angels, you can get in touch with them via their website https://farmangels.org.au/

Water Restrictions & Pool Covers

While water restrictions are nothing new to many areas of Australia (such as Tamworth residents who are currently at level 5), this is the first time Sydney has been affected since 2009.

As a pool owner, one of the most effective ways you can save water is by using a pool cover. An Oasis Solar Pool cover has been independently tested, and proven to prevent up to 99.84% of evaporation.

All our Oasis Solar Covers are licensed under the Smart Approved WaterMark, endorsed by the Water Corporation’s Waterwise program and carry the newly created Climate Care Certification from SPASA.

If your local area has recently introduced water restrictions, it’s likely that having a pool cover with one or all of these qualifications is required in order to fill or even top up your pool.

If you registered your warranty with us and require a copy of your cover’s compliance certificate, just send us a message and we’ll be able to send you a copy. Your pool shop can also log into our trade website and download a copy for you too.

If you’re not sure what your local restrictions are, check with your local council or water authority – they will have the most up to date information for you.

Water Loss. Is it evaporation or a leak?

If you’re noticing your water level dropping faster than usual, it’s a good idea to check if its due to evaporation or a leak.

The first thing you should do is what they call a ‘’Bucket Test”.

How to do the Bucket Test:

  1. Fill a bucket with pool water, about 3cm from the top.
  2. Put the bucket on the first step of your pool.
  3. Turn off your pool pump.
  4. Using a permanent marker or pieces of waterproof tape, mark the water levels both inside and outside of the bucket.
  5. Turn your pool pump back on.
  6. Wait 24 hours, and compare the water levels.
How to do the 'bucket test'.

If the water level on the outside of the bucket has gone down more than the level on the inside, it’s likely you have a leak.

If the water level on the inside of the bucket has gone down by around the same rate, then your water loss is caused by evaporation. This can be resolved by using a pool cover.

Fact #6. Is it ok to leave my solar bubble type cover rolled up in the sun when I’m not using it?

No. You should never leave a solar cover rolled up in the sun – even for a short period of time.

The nature of a bubble cover is to allow the suns rays to penetrate through the bubbles. When rolled up on roller or reel, these can build up heat internally through the multiple layers to the point of expanding the bubbles, over-heating the plastic and in extreme cases,  melting the layers together! The expansion of the bubbles on the flat side of the solar blanket is evidence the cover has been exposed to heat and the Sun when not on the pool. This can cause the cover to appear to shrink in size as the upward expansion of the bubbles, causes the cover to contract and measure less than before the bubbles were expanded.

The excess heat can cause a premature degradation of the plastic in sections across the blanket around the width of the rolled up blanket (around 300mm)  and 900mm apart which is commonly known as “Roller Burn”. This caused by not covering the blanket when it is rolled up on the Reel. The way to avoid this is to always cover the blanket when rolled up on the aluminium tube of the Roller Reel.

Again, you can confirm this by looking at the flat side of the bubbles and seeing if the layer is flat or slightly indented (normal) or raised a little, and this means the blanket has been exposed.

You cannot reverse this damage, but you can prolong the life of the pool cover by preventing any further exposure. Always use the ‘Overcover’ provided with your reel/roller to protect the solar blanket when stored.  If you do not have an overcover, you can purchase one from your poolshop, or you could make one using a reflective tarp.

ABGAL supply an overcover with all Hydrotools branded reels. It is a white, heat reflective poly tarp fabric with a cord at each end, designed to slip over the rolled up solar blanket pool cover.

7 Ways to destroy a solar pool cover and void your warranty

  1. Not turning down automated chlorinators after a solar cover is installed. A cover reduces chlorine consumption by around 50% – if the chlorinator is not turned down, it will produce too much chlorine, and damage the cover. If your chlorinator is already running on its lowest setting, you can reduce the running time slightly, or add fresh water as needed.
  2. Not removing the cover after super chlorination. If you super chlorinate, always remove the cover first, and do not replace it until after chemical levels have returned to normal.
  3. Not keeping chemical levels to within the Australian Standard. Even being slightly over for a prolonged period of time will cause bleaching and brittleness of the cover. We recommend you test your pool chemicals regularly. You don’t need a full breakdown from your pool shop every weekend – just a quick check at home with some test strips is sufficient.
  4. Leaving a floating chlorine dispenser under the cover. While a floating chlorine dispenser is ok, they don’t float so well when they’re jammed under a cover. They will simply sit there, and cause a large concentration of chlorine in one area – and will damage your cover (causing bleach spots/burn), and probably damage the pool finish too.
  5. Leaving the cover exposed to sunlight when not on the pool. Solar covers are designed to attract and store heat. When a solar cover is rolled or folded, each layer gets hotter, and the temperatures build up through each layer. We have seen covers which have gotten so hot the layers closest to the reel have literally melted and fused together. To prevent this from happening, all ABGAL cover rollers are supplied with a protective overcover, which must be used when the cover is not on the pool.
  6. Improper storage. This picture? It wasn’t staged. It was literally what we saw whe7-ways-to-ruin-a-pool-cover-and-void-your-warrantyn we went to visit a pool owner – and they knew we were coming!! They didn’t want it on the pool at the time, so they’d ‘moved it out of the way’ for a few days. When on a reel, or folded, a blanket should be covered with a heat reflective cover. If storing for an extended period of time, it should be rinsed with clean water, and allowed to dry thoroughly before storage – and stored in a covered and protected area, at below 45 degrees celcius.
  7. Incorrect positioning on the pool. A solar cover shouldn’t be dragged over the pool deck, decorative rocks or sharp coping. And it should be cut to shape, so that it moves easily on the water. We’ve heard of people leaving them in a rectangular shape on a kidney shaped pool, then holding the edges down with bricks and rocks to stop them blowing off in the wind!

Pool Shops: How to give your customer a 10 year warranty on a pool cover

warrantySick of losing pool cover sales to that faceless stranger who continues to undercut you on ebay? You can’t beat them on price, but you can beat them on service. Talk to your customer, and help them choose the right product for their needs.

Offer an installation service too – not only do you make a few extra dollars , but by ensuring the cover is installed correctly, you extend their warranty. That’s right – we will extend the warranty on all 500 micron Oasis covers to a whopping TEN years (pro-rata), when profesionally installed.

The extended warranty is only on professionally installed covers, to give you an edge over web sales. All you need to do is arrange for a professional installation of the solar cover, and make sure your customer quotes the name of the installer when registering their warranty with us – we automatically upgrade their warranty from 8 years to 10.

Why did my solar pool cover turn my pool green?

Generally, if your pool turns green, it is because of algae. While algae is pretty much always present to some extent, it can become resistant to normal levels of chlorine, and if the conditions are right, it can take over, in a very short period of time.

Algae loves

1. Low chlorine levels;

2. Phosphates; and

3. Warm water.

If you already have low chlorine and phosphates present in your pool, then adding a solar pool cover (which warms the water) will most certainly help existing algae to thrive.

So while a solar cover won’t actually ‘turn your pool green’, it will warm your water by up to 8 degrees, so if the other conditions are right, adding a solar cover can easily accelerate algae growth, very rapidly.

You need to get the water balance in your pool right before putting the cover back on. Take a water sample down to your pool shop, explain what is happening and they will work out what you need, based on your pool water condition, and set you on the right path. If you wish to do it yourself, (and it is only just starting to turn green), the first step is an algae starver. This will remove the phosphate build up, (the algae food), and thus, the algae starves. Filter your pool for 12-24 hours, to remove all the algae spores from the water.

Its also a good idea to backwash or clean the filter afterwards, to ensure there are no algae spores trapped inside the filter. If there is algae spores left in the filter, you have a greater chance of the problem recurring.

If the algae is really severe (ie you can see it on the pool walls and floor), you really wont be able to avoid a trip to the pool shop. Superchlorination is required, and you will need professional advice with regard to quantities and concentrations of chemicals. Ensure your pool cover is completely removed when you superchlorinate, and do not put it back on the pool until chemical levels return to within the Australian Standard.

If you find your pool water is too warm, you may consider a non heating pool cover like KoolCover – it will insulate the water and stop evaporation, but being opaque, it doesn’t heat the water like a traditional solar blanket.