Nomdaica, I feel your pain. I am in the process of buying
a 36-38’ cruising boat for liveaboard
and cruising and have been racking my brain for months about hot water showers. We will be on the hook most of the time, my admiral will insist on a hot shower even in the tropics, and I do not want to turn the engine
on just for hot water. I have lived on a boat previously, but what amounts to “camping” for 6 months becomes privation longer term. So, let’s accept that we all want a hot shower, and that we want it in the head or shower stall, not the cockpit. (I tried selling tickets to our cockpit shower shows, but people kept asking if we had change for a dollar.)
Looking at the posts in this thread and my research
, it seems there are at least five options:
1. Use a water bag or, better still, the pump-up solar
shower,mentioned by onestep, which does not need to be cranked up high for gravity feed in the shower stall - just add hot water from the stove.
- slightly Inconvenient longer term
2. Use a gas camping style tankless heater, unvented, in the shower
+ no more dangerous than a stove if doors and hatches are open
- possibly illegal, which means a registered gas-fitter will not do it (Ok, I can do DIY stuff, but like most DIYers, I get it right second time round. This is not something to get wrong the first time!)
** Can any resident gas experts comment further on this option? **
3. Use a gas camping style tankless heater, unvented, outside the boat
- what a pain to disconnect and store each time one readies the boat for sailing.
4. Use a power-flued gas tankless heater
+ permanent installation
- not so cheap (e.g. $1450 Precision Temp Boat Tankless Hot Water Heater. Gas Marine Water Heaters. Propane Boat Hot Water Heater
- puts a 3” hole in the cabin
for the flue. That hole must be somehow made watertight, like a dorade vent.
- yet another item vying for space in the boat.
5. Use an immersion heater in the existing (in most yachts) water heater, using 110v or 240v from the onboard invertor, batteries, or perhaps silent generator
to shore up the batteries.
+ uses existing equipment
(if the current
water heater does not have an immersion element, it should be cheap and easy to add)
+ no more space needed
- uses scarce amps
Here are some quick and dirty electrical
calcs for option 5 (please check these – I am no sparky):
* Assume the immersion heater uses 1000 watts @ 110 volts (1000 / 110 = 9.1 amps @ 110 V).
* A Honda
EU2000i produces 2000 watts at 120 V, so you could simply run a generator
for the time it takes to heat the water.
* How long to heat the water? In cold areas (10⁰ C) to heat 25 litres of water to 55⁰ C would take 78 minutes (see Calorifier and Power Consumption - Yachting and Boating World Forums
). In tropical areas, where the water is already around 27⁰ C, you may only need to raise the water temperature to 45⁰ C, so that would take about 38 minutes.
* Alternatively, if running off 12 volt batteries, the 1000 watts now needs 1000 / 12 * 1.15 (inefficiency factor of invertor etc) = 96 amps. For a cruising boat with a large battery
bank, plenty of solar
power, and a wind
genny in the trades, this might be ok for 38 minutes. Beyond that… time for the generator.
plan is to use the (hopefully) existing water heater and see how that goes. If there are ever spare amps (rare with a watermaker
, fridge, blah blah) then heat water opportunistically. Otherwise, if the batteries are low, run the generator for an hour to kill two birds with one stone. If that fails, I will look at the the pump-up solar shower.