Water Budget and Planning | Sailing Blog - Technical Hints and Tips - Sailing Television

Water Budget and Planning

What a wonderful 3 weeks we have had in the Virgin Islands!!! First 2 weeks cruising on our friends “Diesel Duck” - a 42 foot motor sailor immaculately fitted out in Cherry with all the best equipment. Benno and Marlene have been cruising before on a 37 foot steel sloop and decided for their next cruise they would like a power boat. So they built the Diesel Duck and have now sailed from Canada down to the Caribbean as far as Venezuela. We met them in St Thomas USVI and had a great 2 weeks cruising the USVI, over to Culebra and then back upwind to the BVI. It was especially nice to have a chance to try out and live with modern hi-tech equipment, some of which we are planning on installing on the new boat. With an 800amp-hour battery bank, and large inverter, watermaker, washer-dryer and a diesel generator, Diesel Duck gave us first hand experience of managing water and electricity on a modern well equipped cruiser. We were filming for “Distant Shores” of course, and the weather was great. Thanks guys!!

Water Budget

The first thing I learned was just how much water a modern cruising boat could use. On Two-Step we have only foot-pumps for the water – no pressurised system. And no real shower. So our four 80 litre water tanks will last us 2 weeks or more with the two of us on board. But a modern boat with pressure water tends to use more. It is just not possible to wash your hands of brush your teeth with as little water as we use with our foot pump. Similarly washing dishes tends to use more when you have a regular tap. One of the biggest factors is water supply. On Two-Step, we do not have a watermaker. So an ocean crossing passage of 21 days (our longest to date) means we have to make our 320 litres last that long. For anyone planning ocean passages, note that you must budget your water for as long as you might be out there. We usually add a 50 percent safety factor to our voyage planning when we are provisioning. So our Atlantic Crossing to Brazil of 2200 miles was planned to be at sea for an entire month. We had enough food for that, and planned the water for that as well. Since we have four tanks, we know we shouldn't finish more than one per week.

Anyway, the net result of this is that long ago we learnt we could make do with just 80 litres of water a week for the two of us. Sun shower and sponge baths, washing dishes in salt water, and using foot pumps to help conserve.

Enter the modern cruising boat!! I read in a cruising magazine not so long ago that you could budget 25 gallons per person per day!!!! Are they talking about life on a cruising boat of on the QE2 I thought? Well, it turns out that if you have all the gadgets you just might (although 25 gallons might still be too much even for those who leave the water running while they brush their teeth).

Water Budget Factors

* Toilets – some modern marine toilets hook up to the fresh water to flush. If you have these on your boat then factor in 3 litres per flush. Possibly 20 litres per person per day.
* Showers – a modern shower can use quite a lot of water. Its a great luxury to have a shower on board, and many cruisers have them. If used frugally they may use just 10 litres per shower or even less if you instruct crew to turn it off while soaping up. I haven't done clinical tests but I imagine a wasteful shower head just left on all the time would use more than 20 litres in a long shower.
* Pressure water syndrome – probably the most insidious – PWS (pressure water syndrome) affects people by encouraging them to just leave the water running. Where campers and old-time sailors know its easy to brush your teeth in just 1 cup of water, modern city dwellers afflicted with PWS can use 10-20 times as much. Choosing a faucet that is easy to turn on and off can help somewhat. And instructing the crew can help too.
* Watermakers – For the new boat I am looking at a watermaker that will produce 24 litres per hour. To supply our modest needs on Two-Step, this would only need to run one hour every two days. Even when we are more careless and use water more casually we would still only need to use it for 1 hour a day. The factor seems to be you will use more since you know you have it! Cruisers I have spoken with who have watermakers, all said they wanted one so they wouldn't have to worry about water use. So add a factor of 2-times if you are in this category. Just remember that nothing is free. Running a watermaker for twice as long as you need, will use twice the power. It also might be noisy. Check out the sound of a potential watermaker before you buy. Many people recommend you plan a watermaker to supply your water needs by running in the time you will be running your engine or generator to charge the batteries. The rational here is that watermakers use a fair bit of power, so you will want to run the generator or engine at the same time. So a watermaker that is too small will need to run for hours. The alternative is a smaller watermaker that you might be able to run during times your solar or wind generator is producing surplus power. But more on power generation later...

See you next time – in the Med when we are back aboard Two-Step in Malta for Easter.
blog comments powered by Disqus