Domestic Water System

Our approach to domestic water systems has evolved over the years, with the introduction of ever more efficient reverse osmosis watermakers.

On our sailing designs, where we want to minimize passaging weight to enhance performance, fresh water supplies are limited to what would be required in the event of a watermaker failure.

On Beowulf, as an example, we carried just 50 gallons (390 liters) of fresh water (out of a capacity of ten times this much) on passages. To ensure reliability, she had two small 24V DC watermakers.

With this new boat, the game changes entirely. Now we want to passage at the heavy end of the displacement range. It is a little less efficient, but the small increase in fuel cost is more than made up for by comfort. As a result, we make fresh water each day at sea to offset what we consume in the way of diesel fuel. This ends up being around 160 gallons (600 liters) a day. Needless to say, we end a passage with large volumes of fresh water in our tanks. Because we have so much water already on board, and because the watermaker itself tends to be larger, our water consumption has grown accordingly.

Our approach to designing the fresh water system, has from the start, assumed that we’d be using lots of this once precious commodity. Fresh water is used for the usual bathing, cooking, and drinking-related activities. It is also used for flushing two of the three heads, for ballast (as previously mentioned), for the clothes washing cycle, and for rinsing salt off the boat. Fresh water capacity on Wind Horse is roughly 1900 gallons (7400 liters).
Our basic rule is to make or catch our water, and avoid, if at all possible, taking on local water. This applies in first as well as second and third world countries. We have two sources for water. One is a Village Marine 40-gallon (155-liter)-per-hour RO system. This is powered by a 230V AC motor, and runs off the genset or one of our inverters. This RO system is bare bones. No automatic features, manual fresh water flush, and very little to go wrong. So far it has worked without a hitch.

The watermaker control is located just inside the door to the engine room. It can be adjusted without actually entering the engine space.

There are inspection ports through the engine room door, so the watermaker gauges can be checked without opening the door – handy when there is someone sleeping aft and we are trying to keep down the noise level.

The second source for water is our deck collection system. Open the deck fills to the aft tank, and within a couple of hours of a moderate rain storm, we have collected close to 900 gallons (3500 liters). We have used this system Fiji, Samoa, and Alaska when sitting for longer than a few days at anchor. Catching rain water reminds us of the olden days when this was our only reliable source, and reduces the need to make water with the generator.

Our choice for a pressure water pump was a double-action, 7-gallon (26-liter) per minute Shurflow pump. This pump includes a small accumulator tank, and is the same pump used elsewhere for wash-down, ballast fill, and watermaker presupply. Except for some minor problems with the pressure switch, it has served us well.

Water is pumped around the boat in a 3/4″ (19mm) ring of hot and cold using a plastic home-style patented system. The various fixtures are connected using 1/2″ (12.6mm pipe).

The hot water circuit goes all the way around the boat, starting and stopping at the heater in the engine room. There are check valves in line and a 230V AC circulation pump.

The pump is run for a couple of minutes before we do the dishes or take a shower. This brings hot water around the boat, so none is wasted waiting for warm-up.

The heater is a critical part of domestic bliss. High on the priority list is having sufficient capacity for the long showers made possible by all this fresh water. We’ve been doing this for years by using the ship’s heating system to also heat domestic hot water. When in the tropics, we still use this system, but do not circulate water to the fan coils.

We are using a Kabola diesel boiler, with a built-in domestic water heater. There is a setting for just heating the domestic water tank, which is what’s in use right now. This is a 65,000 BTU diesel boiler, way more capacity than is required for domestic water needs. The result is that we never run out of hot water. You could take a shower that consumed all 1900 gallons, and at the end, the water would be just as hot as when you started. If the heater has been off, it takes about two minutes to fully heat the water tank on start up.

Something new for us this time is the use of constant temperature shower valves. In theory, you set the temperature, and then the valve adjusts to changes in pressure on the hot and cold circuits. We were dubious, but wanted to give this a try. We are happy to say that these constant temperature valves do work!We have been in the habit of fitting one stainless drinking water tank to most of our aluminum boats. On this design this is a 20-gallon (78-liter) stainless tank, which sits in the basement. This tank is accessed with a Whale foot pump at the galley sink. With this system, we always know we have a minimum of this much capacity should the watermaker fail.

One final thought. This profligate use of fresh water needs to be viewed in light of how we cruised in the past. In the days before watermakers, we would happily exist on five gallons per day for two adults and two children. This small amount of fresh water, plus lots of salt, was consider luxurious in the 70s. We once spent an entire year cruising in Melanesia and northern Australia without once taking on water from a dock. We caught everything we used.
When we’re luxuriating in those long hot showers, or sudsy baths, we often think back to how it used to be. We like it better now!

Posted by Steve Dashew  (October 20, 2011)

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