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Community Contribution - Rainwater catchment

Community Contribution - Rainwater catchment

I’ve often wondered why catamarans aren’t built incorporating a rainwater catchment system?

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Raul Guitron
November 30, 2021
Hi! Hope im not late in the topic.
Maybe there could be a mesh that can be rised at night to get water by condensation? Here a short video about it https://youtu.be/YxRONAZoMDk
July 23, 2021
Voilà une chose intéressante et nécessaire, c'est même incroyable que ce ne soit pas systématique sur tous les bateaux cat ou mono.
Olivier Verschoore
June 15, 2021
Hello Pierre, Francis and Herve,

The habit at home is to have drinking water for everything. On a boat water can be drawn for different "tanks": salt water is suitable for many things (even a shower to rinse off) and available in unlimited quantity, rainwater is ok for shower or the last rinsing of dishes, finally drinkable water can be reserved for cooking and drinking and does not require large quantities. Having separate circuits and tanks with those different waters and a device to monitor the consumption and to estimate rainwater to come would be my choice.

Best Regards

June 15, 2021
It will depend on each owner's use, for that I would suggest the collection gutters to be incorporated in the design. Water would be drawn to a place where it would fit a filtering system (UV?), then to the fresh water tanks; being drained to sea if capacity is full or you don't have the equipment. Anyway, it is not a difficult solution, and an important addition. Even with an active filter, its power consumption should be way lower than the water maker.
June 9, 2021
This comment has been deleted by the user.
June 9, 2021
2 answers

Thank you for your contribution to Excess Lab. It fits perfectly with the concept of the Lab and opens an environmental topic in line with the values of Excess.

Water on board, just like energy, is one of those 'consumables' that can limit our range under way.
Being able to increase our water capacity, in a self-sufficient way, allows us to consider undertaking longer passages... without weighing down the boat!

Desalination systems are of course a first answer, being the most widespread, and best-known and mastered.
It’s a relatively light solution; there’s an unlimited supply of the raw material(!); and it is ecologically much better than drinking water from plastic bottles.
On the downside, it has a high initial cost, requires maintenance, and consumes energy to work...

Rainwater is a less often considered alternative but (on paper) an even more attractive one, because it is totally free and doesn’t require any complex and expensive equipment.
Rainwater can be recovered with simple filters, and consuming no fuel. It’s just that the availability is somewhat... random!

Numerous experiments have been made, from the single-handed sailor taking a simple shower, to the perfected system offering water as pure (or even purer) than bottled water.
Some common points emerge from these experiments:
- The need for a large catchment area: To make the most of the slightest rain shower, you need surface area. From this point of view, a catamaran makes a much more suitable platform than the deck of a monohull!
- Clean catchment area: This input data is less simple, salt water, dust, bird droppings are all pollutants that must be removed from the circuit.
- Good filtration and treatment capacity: Directing rainwater to a water tank, without filtration or treatment, does not provide clean water for consumption.
- Storage capacity: Since rainfall is random, you really need a significant storage capacity to achieve autonomy with rainwater.

With these elements in mind, collecting rainwater on an Excess catamaran seems perfectly realistic. Of course, this is too random a source to fully rely on, but it can be both an economical and ecological supplement to the water carried, for any crew looking to head off on longer passages or cruises and accepting to put up with the constraints of filter maintenance.

Within the framework of Excess Lab, we would be very interested to hear the opinions of other users on this subject: Would the Excess of your dreams have a coachroof designed to collect rainwater? Would you be willing to manage the collection, storage and treatment of rainwater? Everyone's opinion is welcome. If some of you have experience in this matter, it would be very interesting to share it on this thread.

Looking forward to hearing any more feedback, and thanking you again for this very constructive input,
Kind regards,

Hervé Piveteau
Product Manager - Excess Catamarans
Pedro Rodrigues
April 30, 2022
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Pedro Rodrigues
April 30, 2022
It would be perfect, specially in a tropical country such as Brazil which doesn't have a drinkable water in many marinas of small towns, and it rains a lot specially during summer. Considering the hard rooftop as the perfect area for catching the rainwater and that some boat have only one tank of water, that would be the perfect sollution.

BTW, another downside of a watermaker is that sometimes the anchorage doesn't provide you a clear enough water to run it. If you do so, you will need to change your filter pretty often.
June 1, 2021
Tres utile, notamment sous les tropiques avec abondance naturelle. En plus la "gouttiere" peut servir de main courante. Faut un systeme simple / robuste de vannes pour evacuer les 1eres mn de pluie avant d'envoyer sur le reservoir.