Collecting your own seawater has a number of benefits:
The most important thing about collecting seawater is ensuring the collected water is as clean as possible and free from pollution. An appropriate site must be chosen and water collected at the right time.
Selecting an appropriate site
Ideally, water should be collected from a site on the ocean, as far away from mouths of rivers or other areas of land run-off. Harbours and bays fed by rivers are usually not appropriate as the water may contain a lot of run-off from the land. Additionally, the site needs to have enough protection from swell and wind to make collection safe and to ensure the water is clear. Small bays or inlets that are open to the ocean are often the most appropriate. These provide sufficient protection but still supply good clean ocean water.
The site also needs to have relatively easy access by car, otherwise the water is going to have to be carried over too great a distance.
Boat ramps are often a good compromise. They provide easy access by car and are usually somewhat protected. You must be careful to ensure the area around the boat ramp is clean and free from pollution, including fuel from boats. Note that heavily used boat ramps, particularly those in harbours may not be very clean and you may be competing with many boat users. Be aware that you may need to park on the boat ramp for up to 30 minutes.
Check all potential sites for influence of rivers or streams but also for sewage outfalls. For Sydney, the following information is available: Coastal sewage treatment plants operated by Sydney Water. Check with the local sewage treatment authority in the proposed locations.
It is wise to have more than one site from where water can be collected, particularly if the sites face different directions and are exposed to different conditions. That way, if the prevailing winds and swell make one site unavailable, the other site may be available.
Some appropriate sites around Sydney include:
When to collect
It is best to collect as close to (but before) high tide as possible. This ensure that there has been an influx of clean ocean water. Times of tides can be checked at: Tide Predictions for Australia, South Pacific & Antarctica.
The coastal weather forecast should be checked before heading down to collect water. High winds or swell can make collection difficult and can also result in dirty water. For New South Wales waters, the NSW Coastal Waters Forecast. The Bureau of Meteorology site includes forecasts for other states. I have found that if the seas or swell are more than 1.5m or the winds are more than 10 knots, collection is very difficult.
Collection should be avoided after heavy rain. Heavy rain will bring a lot more water down rivers and stormwater drains and this water may stay close to the coast.
Methods of collection
There are a number methods that water can be collected and the choice of method may be dependent on the method of transport of the collected water.
The most straight forward method, albeit not very convenient, is to simply wade out into the water with the transport containers and fill them directly. This is OK in Summer, but Winter water temperatures will not be pleasant to say the least.
Water can be collected in a bucket and transferred to the transport containers. The easiest way to do this is to tie a rope to the handle of the bucket. The bucket can then be thrown out into the water and reeled in without you getting wet. If the transport container has a small opening, a funnel may be required.
The quickest and easiest method of collection is with a water pump. A battery or fuel driven water pump is submerged in the water and piping is used to deliver the water directly to the transport container(s). See Water Collection Pump for more information on this method of collection.
Methods of transport
Once the water is collected, it must be transported home. There are a number issues to be considered: safety, road rules, protecting your vehicle and transporting the water from the vehicle.
Safety should be the first consideration in deciding how to transport collected water to your home. Containers must be secured so they can not move around with the motion of the car. Additionally, consideration should be given to the movement of the water inside the container. Water in a partially full container will move with the motion of the car and this will shift the weight around possibly making the car unstable. It is best that transport containers are completely filled so there is no movement of water in the container.
The weight of the full container(s) should also be considered. Seawater weighs just over 1kg per litre and you must ensure you can safely carry the weight of the volume of water you expect to transport. Check the manual for your vehicle to ensure the vehicle can handle the load.
It is advisable to check the local roads and traffic authority regulations on loading vehicles (and trailers if one is to be used).
Containers used in the transport of water should be sealable to prevent the spillage of water in the car. Seawater is very corrosive.
Consider how water will be transported from the vehicle when you arrive home. For example, a 300L container full of water is going to weigh more than 300kg and will be difficult to carry.
I have found that for me the most convenient method of carrying seawater in my car (Commodore wagon) is multiple 25L "cube" style containers. These can be easily filled and sealed. At 25-30kg full, they can be easily carried either singularly or even two at a time over short distances. They can be stacked (for storage).
Currently, I carry 12 25L containers in the back of the wagon. This allows me to collect 300L of water at a time. I will shortly be buying a 6x4' trailer that will allow me to carry 24 containers, increasing my collection capacity to at least 600L per trip.
Last updated: February 23, 2003