Swimming pool covers
WTR08
Reduction in water consumption, reduction in energy consumption, reduction in chemical usage and extended periods of usability, these can all be achieved by installing a cover to your swimming pool. This conservation measure will focus on reductions in water loss but will touch lightly on the other benefit.
From the moment you fill a swimming pool with water you begin to lose that water to evaporation, as the liquid turns into a gas or vapor and disappears into thin air. The process is almost inevitable, with only the rate of evaporation varying. As a pool owner or operator you can reasonably expect to lose tens of thousands of litres of water per year. To understand your opportunities to reduce water loss first it will be useful to understand the cause of the evaporation.
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Factors affecting evaporation rates
Surface area - all of the following factors which determine the rate of evaporation act upon the surface of the water, therefore it follows that greater the surface area of the water the greater area the negative factors have in which to cause evaporation. The greater the two dimensional size of your pool, the greater your water loss will be.
Temperature - Heat increases the rate of evaporation, so you can expect your water to evaporate faster if you live in a warm climate, and slower if you live in a cold climate.
Humidity - The quantity of water than air can hold is not infinite and varies with the air temperature, hence the term relative humidity. If the air surrounding your pool is low in humidity it will have greater capacity remaining to absorb water from your pool. Inversely, if you live in the tropics with air with a high relative humidity it means the air is already holding a lot of water, meaning their is less capacity for it is absorb water from your pool. Low the humidity, the greater the evaporation.
Surface exposure - the more the surface of your pool is exposed to air movement the greater your water loss will be. That gentle breeze that causes the surface of your pool to ripple is more than enough to promote greater evaporation rates.
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How To Calculate Your Water Evaporation Rate
There are pool evaporation calculators you can use which can be fairly accurate, if you put accurate information into them. However an easy way to determine your water loss. For this, we recommend the Bucket Test:
Measure the surface area of the bucket....do you remember π x r^2. Fill a bucket with the water from your pool. Using the pool steps or possibly the shallow end of the pool, place the bucket in the water so the rim is just above the waterline. On both the inside and outside of the bucket, mark the water level with a marker or some tape. Wait a full 24 hours. Check the results and measure how much water was lost in the bucket. This is your daily evaporation rate per bucker sized surface area of water. Now divide the surface area of the bucket by itself to get to one and do the same with the total water loss. This is your evaporation rate per unit of surface area, multiply this by the surface area of the pool and you will have a fairly good idea of your water loss per day from the entire pool.
Why wouldn't you just mark the side of the pool and do the same? Many pools leak, measuring evaporation rate of the entire pool would not allow you to discount a leak being the cause of water loss. It is recommended that as the bucket test finishes you look at the water level around the outside of the bucket. If, after performing the test, the water level on the inside of the bucket is noticeably higher than on the outside, you may well have a leak.
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Benefits of pool covers
Market leading covers will reduce water evaporation by greater than 90%, which can be a quantity of water. Alongside the water conservation benefits there are a number of less obvious benefits - they will keep your pool warmer, potentially enabling more months of usage and lower pool heating costs. You will also reduce your chlorine usage, UV light breaks down chlorine, installing a cover will reduce the rate at which the chemical need sot be replaced. Putting this all together a pool cover will contribute to many factors in a typical sustainability plan.