hot water options

[Ronnie B]

Hi, Ive been living on my boat now for 2 years and been very happy with my Webasto heating and hot water system . However recently my 110 ltr hot water sprang a leak (water spurting out of the side) . So initially I'm thinking I need to instal a new tank ..but then wondering can I get a gas on demand water heater and just do away with the hot water tank but keep webasto for heating ? Any comments on this would be useful Thanks in advance 🙂

[Ex Brummie]

If the boat is subject to RCD, then an instantaneous heater would need to be room sealed. If an older boat that has not had one fitted before, you may get resistance when next BSS is due if you fit a Morco, or equivalent.

[BEngo]

What you suggest is possible.  It may turn out to be a non-trivial plumbing job though. Locating the exhaust vent in the roof,  while getting a long enough flue pipe to comply with the installation instructions, but short enough to not hitt every third bridge hole with the flue can also be difficult.

 

Quite a few of the modern instantaneous water heaters rely on a continuous 240 V supply for things like ignition and exhaust fans..  Ok if you have an inverter in all thd time, but otherwise a PITA.

 

They all use quite a lot of gas.  Make sure your gas pipe and the regulator are big enough to supply the heater and whatever it already supplies.

 

N

 

 

[Jen-in-Wellies]

Welcome to the forum.

The hot water tank in boaty language is called a calorifier, or on this forum, a cauliflower. 😀

As the other replies have said, instant gas heating is possible, but more work than you'd at first think. Easiest and probably cheapest is to replace the calorifier. Do you know if the one that broke is a proper marine calorifier, or a domestic hot water cylinder? If the second, then it is possible it wasn't designed for the pressures you get from a boat water pump. Another cause of even proper calorifiers failing is not having an expansion tank in the hot water side of the system. Pressure increases as the water heats up and expands. The expansion tank relieves the excess pressure on the copper cylinder. There is a pressure relief valve usually too, but it doesn't do to rely on this. Long term, the expansion and contraction will lead to cracks and leaks in the cylinder. I had one fail this way after only a few years.

[blackrose]

On 27/02/2023 at 10:36, Ronnie B said:

Hi, Ive been living on my boat now for 2 years and been very happy with my Webasto heating and hot water system . However recently my 110 ltr hot water sprang a leak (water spurting out of the side) . So initially I'm thinking I need to instal a new tank ..but then wondering can I get a gas on demand water heater and just do away with the hot water tank but keep webasto for heating ? Any comments on this would be useful Thanks in advance 🙂

 

Why would you do away with the calorifier? You just need a new tank or a repair - and try to establish why it leaked in the first place so it doesn't happen again. As Jen says above, if you have a NRV on your cold water feed to the calorifier and you don't have a hot water expansion vessel (basically an accumulator tank) Td into the system after the NRV then you've got a hot water pressure vessel that's relying only on the PRV on the end of the calorifier to release the pressure in the system.

 

Anyway, my main point is that as a liveaboard you don't just rip out systems on boats because they have a problem. You want as many different ways for producing hot water as possible so that if one goes down you have another available. So by all means install an instant gas water heater if it's suitable and passes the regs, but install it in addition to your calorifier. 

Edited March 2, 2023 by blackrose

[Alway Swilby]

Is your calorifier also heated by the engine when it is running? If so it seems a shame to loose that free hot water.

[bizzard]

1 hour ago, Alway Swilby said:

Is your calorifier also heated by the engine when it is running? If so it seems a shame to loose that free hot water.

It isn't entirely free. Whilst heating the calorifier the engine takes longer to reach normal running temp, therefor using more fuel. A bit like car headlamps, most folk think they come on for nothing, they don't, also use more fuel as the alternator puts more load on the engine. There aint nothing free.

[Alway Swilby]

50 minutes ago, bizzard said:

It isn't entirely free. Whilst heating the calorifier the engine takes longer to reach normal running temp, therefor using more fuel. A bit like car headlamps, most folk think they come on for nothing, they don't, also use more fuel as the alternator puts more load on the engine. There aint nothing free.

Yes, I nearly stuck an "almost" in there but then decided against it.