Although I spent most of my cruising years within 20 degrees of the equator, the landlubber luxury I missed most was not air conditioning (I’m a warm-blooded type), but a hot water shower.
We used a solar heated “sun shower” for most of our bathing needs. On a sunny day, the 1-gallon flexible plastic bag with one transparent side would deliver water that was plenty hot, but the drizzle of water usually left me unsatisfied. Friends used a manually pressurized garden sprayer which they had painted black. This added a bit more pressure, but like the collapsible foot-pump pressurized Helio shower we tested back in 2016, it was most effective in sunny warm climates. (Chapin now makes a black polyethylene industrial sprayer, in addition to their translucent garden sprayers.)
As I go about with the refit of Opal, the 1971 Yankee 30, my biggest challenge is deciding which of the comforts I missed during my life aboard Tosca I’d like to add. A below-decks hot water shower would be nice. Since a Lake Superior cruise is high on my bucket list and having spent the last two so-called “summers” in Marquette, MI, I’m pretty sure I won’t get the same performance out of my sun shower as we did in Fiji.
What about a tankless propane heater? You will see these on boats, but as we’ve found in the past, the propane systems are generally not safe on boats. The folks at Seaworthy published a safety alert regarding on-demand water propane water heaters a few years back which spells out the problems with these systems. Because of the associated risk, they are not compliant with the American Boat and Yacht Council‘s standard. Although I think this risk could be manageable, it could invite insurance claim squabbles if there’s a fire, and I’m trying to reduce or eliminate my reliance on carbon-based fuels.
Since we last looked at boat heating options, advances in renewable energy and energy storage coupled with the explosion of interest in off-the-grid living has led to a variety of other options for moving heat where you need it. For those with a surplus of power (and bigger wallets). Two of the bigger names in marine heating, Webasto and Eberspaecher offer some dual water-air heaters with good reputations in the marine world. But when you include all that is required, these systems can be expensive. If a “marine” 12-volt water heater like the ones we tested is out of reach, there are some less expensive 12-volt options aimed at RVers. Computer nerds will no doubt enjoy the Everlander’s YouTube video on building their solar powered water heater, using a converted Rheem water tank. (Note that they have a massive rooftop solar array, impractical on most boats.)
Given my budget and experience with landlubber materials at sea, I’m leaning toward one of the marine water heaters that Practical Sailor has tested in the past. My next step will be figuring out where to fit it. Here is tester and marine surveyor Frank Lanier‘s assessments of the installation process:
The physical installation of a water heater may seem pretty straightforward, but the devil is indeed in the details. It starts prior to purchase, with a search for adequate space that’s relatively near the engine and vertically as low as possible. Next is bonding in a well-reinforced surface to mount the water heater onto. The empty tanks are relatively light, but if you add 45 to 88 pounds of water, you can see why a sound support base is important in a rough seaway.
Plumbing can be a bit of a challenge, especially when it comes to trapping air bubbles that will cause the engine’s coolant pump to cavitate. Every diesel engine circulates coolant with a vane-type pump, and though its long-term reliability is legendary, this type of pump is not a positive-displacement pump. That means it is not self-bleeding, so if air bubbles are not bled from the system, the pump ingests the air and spins little or no circulating water. This is one of the reasons why remote surge or top-off tanks for coolant are always placed higher than the engine itself. It’s also why there’s also a butterfly bleed valve on the top of heat exchangers.
In situations where the heat exchanger in a water heater has an inverted U-shape, with the inlet and outlet lower than the high point in the loop, care must be taken to rid the coolant circuit of all air bubbles when refilling with water and antifreeze. Air always seeks the high point, and this is another reason why some manufacturers say that their water heaters should be mounted at or below engine level, nearly impossible on many sailboats.
Globalization has made plumbing more difficult, and unless you have a good source for metric bronze pipe fitting, it’s vital to purchase metric-to-NPT conversion couplings (usually available from heater vendors).
To keep pipe joints from leaking, use Teflon tape or pipe joint compound and remember that hose barb-to-hose connections are much easier to make drip-proof with a hose clamp than the same connection made on a threaded pipe stub. (See our test of tapes and thread sealants in the November 2021 issue.) Care also needs to be taken when connecting stainless-to-stainless joints, in order to avoid galling the threads. Many European marine plumbing manufacturers have switched to high-quality, investment-cast stainless steel. Nevertheless, these fittings are not as malleable or corrosion resistant as silicone bronze, so be sure to not over-tighten or allow stray DC current to run through these fittings.
If you are shopping for a water heater, our in-depth report on water heaters is a good place to start. I’d love to hear about readers’ experiences with hot water systems. You can add them in the comments below, or send to me firstname.lastname@example.org.