The proposal to use sea water to top up domestic swimming pools as a water conservation aid has met a dubious response from representatives of the pool industry.
They point out that sea water is significantly more salty than even salt-water swimming pools and that it could corrode such equipment as pumps.
In addition, the high salt content would make it difficult to maintain a healthy chemical balance in the pool.
But the potential water saving is significant: with an average pool capacity of up to 50 000 litres, it takes 32,5 billion litres of water to fill the estimated 650 000 swimming pools in South Africa.
The Western Cape has 14 percent or about 91 000.
The sea water proposal is one of several conservation measures being considered seriously by the City of Cape Town as the water crisis grows.
But no research has been done on the feasibility of the idea.
Dave Regester, general manager of Penguin/Pelican Pools, pointed out that as well as the initial water load required to fill a pool, it needed to be topped up about once a week.
During hot weather, a pool level would drop between 5mm and 10mm a day from evaporation alone, and more water might be lost through boisterous swimming and splashing.
If the sea water proposal became a reality, households would probably need a weekly service to keep their pools full, and transport costs would probably be significant.
Road tankers of the kind used to transport petrol hold between 35 000 and 70 000 litres.
This means one tanker would be able to fill less than two standard-sized pools on any one trip or only top up a limited number of pools.
People with homes in water-stressed areas without piped water - such as parts of the West Coast - pay about R1 000 for a delivery of 10 000 litres of potable water over a fairly short distance, and say about 75 percent of the cost is in the transport.
Transport costs therefore translate to around 7,5c/l.
If the same cost structure applied, pool users could pay at least R75 a week in transport costs to top up a pool by 1 000 litres.
Some pool installation companies warned that sea water could cause problems with marble-coated pools and other pools with fittings not designed to cope with a high salt content.
Most salt-water pools have a salt content of just 0,5 percent, whereas sea water contains about 3,5 percent.
Adrian Meyer from Water Lines said that salt could cause corrosion on parts of pool pumps.
Meyer pointed out that even sea water would need to be sanitised to keep it clean by adding chemicals such as baking soda (sodium bicarbonate) or hydrochloric acid.