With winter coming to an end (we hope) and the hot water on our boat coming from two sources; the fire and the engine, it was looking like the kettle was going to be the only way to make hot water.

However after some random googling I found something called a “Willis heater” which is kind of an External Immersion Heater

A Willis type immersion is a small copper vessel with an immersion heater element inside located outside the hot water cylinder, it heats the hot water cylinder by creating a gravity circulation, this means that any hot water it heats is fed into the top of the hot water cylinder thereby giving enough hot water for dishes say after about 10mins, the power consumption is about 2.9kw compared to an instant heater at 8-9kw. The big advantage a willis heater has over a standard internal immersion is that it will only heat up a little water or the whole tank if you want, the standard internal heater will generally just heat up the whole tank.

Nice I thought 🙂

Now to find one and fit it… Amazon led me to this Willis Heater for about £42, a few days later Mr Postie (sometimes the postal worker is a woman, but not that day) delivered it:

So on paper the installation would be easy… take a 13A switched spur from the distribution panel and feed it to the heater

on paper everything is easy

on paper everything is easy

I mean what could go wrong? so off we go with some plumbing

And time to pressurise the system, after all it has all gone well so far!

Oh look, it went wrong

Oh look, it went wrong

Yep a leak! how do you fix leaks on boat? oh yes self amalgamating tape! that will work!


and no before you ask… it also failed 🙁 so plan, (what are we up to now?) oh next plan!


Right after careful re-fitting of the re-fitted thing we have success! all joints water proof, next challange to power up the system 😀


All working, what could go wrong? Oh I had to ask didn’t I… the pipe from the very top of the water tank to the top of the willis heater was a piece of original plastic pipe, and the thermostat on the willis heater was set to 85oC… guess what happened… the willis heater boiled the water and the pipe gave up and went home 🙁

So after refitting that part with a bit of copper pipe carefully bent to shape using my halon gas fire extinguisher as a former and sat looking at silly angles into the cupboard to turn down the thermostat.

Yes the adjustment is on the _bottom_

Yes the adjustment is on the _bottom_ with no space to see

It is now all working 😀 just need to find someone small to turn the thermostat up to 55oC and everything will be working 😀