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Boats Hot Water Tanks


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As to the last time I was on a Hired Boat there was Two of us on there as the First person having a Shower fine when its my turn having a shower the Water started to turn Cold even though we've been Cruising for 3 Hours or so that Hot Water Tank should still be  some what Hot even after Two Showers do theses Hot Water Tanks have a problem ? or are they Smaller then Standard Home Hot Water Tanks . So how do I avoid this situation next time as I will be on the Broads again in March 2021 that's if Cov19 restriction's allows us?

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Have the first shower.

Seriously though, the tanks are very small in comparison to one you would have at home, mine is 35 litres and is not adequate for two luxury showers in a row, especially if Matron washes her hair.

One answer is for one of you to shower when under way so the cylinder has chance to reheat before you moor or plug into shorepower if the boat has an immersion heater.

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3 hours ago, psychicsurveyor said:

Have the first shower.

Seriously though, the tanks are very small in comparison to one you would have at home, mine is 35 litres and is not adequate for two luxury showers in a row, especially if Matron washes her hair.

One answer is for one of you to shower when under way so the cylinder has chance to reheat before you moor or plug into shorepower if the boat has an immersion heater.

Swancraft fitted large well insulated calorifiers meaning lots of hot water which even kept warm overnight.  

But as PS says generally not much capicity. We never shower before setting off, usually underrway so one can shower while the other takes the helm. Water heats quicker too and no running engine on moorings! :default_norty:

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Showering on a boat is a very different affair from having one at home.  Turn on the shower and wet yourself down, turn off the shower while you apply shower cream etc then turn the shower back on to rinse off. 
We get two good hot showers using this method and our Calorifier is only 35ltrs. 

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1 hour ago, BrundallNavy said:

Showering on a boat is a very different affair from having one at home.  Turn on the shower and wet yourself down, turn off the shower while you apply shower cream etc then turn the shower back on to rinse off. 
We get two good hot showers using this method and our Calorifier is only 35ltrs. 

That is exactly how we do it, usually with at least one shower on the go if not both, we only have about 25 litre calorifier and it's only that big because the base 'prolapsed' after I changed the pump pressure and prv and added insulation, I'm still waiting for it to split but been like that two years now.

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One of the benefits of the English Public School system and compulsary CCF, (You had to join the Scout Troop if you were a Conscientious Objector at our gaff) was you were taught how to "Bucket Bath" on the arduous training Course prior to being dropped off miles from the nearest road to survive pretty much off the land.  I used to love AT and willingly gave up a week of our generous summer holiday to rough it miles from anywhere.

When I did the Azores and back in a Folkboat I had two buckets and seawater soap, it was fine being warm as I did not wear clothes much of the time, salt soaked clothes are a nightmare as they just don't dry.

But my age and lifestyle, years spent on the water and beaches with Judith and our family have had consequences. I suffer Basel Cell Carcinoma as a result of cumulative exposure and whilst not in the same category as Melanoma it is still a bl**dy nuisance as instead of taking 18 weeks to get it whipped off as the NICE target lays down it is taking around 45 weeks in Norfolk.

So slap on the Sun Block and wear a Tilley or other UV protection hat. Personally I wear UV 50+ trousers, shirt, hat the lot in summer now becsuse it is such a fag when it erupts.

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You need to understand the basics of these systems. 

A 35 litre hot water tank will hold 35 litres of hot water. Easy so far. 

Now, you take 10 litres of hot water out of that tank. How many litres of hot water do you have? If you think 25 you're wrong.  

What has happened to the space the used 10 litres took up? 

Yep, it's replaced. By COLD water.  So now you still have 35 litres of water, but its not as hot as it was and this process continues the more you draw out. 

A 35 litre tank really isn't big enough for decent showers. 

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44 minutes ago, FreedomBoatingHols said:

A 35 litre tank really isn't big enough for decent showers. 

Good for social distancing though, everyone stays away.... (a good chewy stout also works well)

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I had to look it up as to what our calorifier details are, found them as per below along with Feb 2007 prices.  The type onboard 'B.A' is the double skinned variety - No coils, it is proper well insulated meaning a shower the next morning is easily doable.  Insulation is the key.  The above post by Freedom is correct, however the cold water going into the tank lies at the bottom and the hot water is drawn of the top of the tank, or should do

WH45B  -  Calorifier, 45 Ltrs inc. 230v 1000w element and connection kit  -  £435:93

WHHOSE16  -  7 x metres Calorifier hose, -30c to +160c  -  £76:09

HG025  -  8 x S/steel heavy duty hose clips (for Calorifier hose)  -  £10:96

Griff

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There’s another way of doing it. 
Find your space, measure up and get it made. 
At least that’s what Richardson’s have done to our ex hire. 
massive tank but flattened so it can fit under bed. 
unlagged  but a quick visit to a builders yard and it’s ready for winter. 
Stainless steel by the look and as an added bonus a nice gentle warmth radiates to the mattress  

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The most efficient hot water tank is as described a tall vertical double walled cylinder with the cold feed at the botton and the hot exit at the top. Minimum external surface area, minimum mixing of cold with that already heated, maximum insulation. That is why in every other application they are made that way. 

Once you start mounting them on their side etc it is a compromise,

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23 minutes ago, ChrisB said:

The most efficient hot water tank is as described a tall vertical double walled cylinder with the cold feed at the botton and the hot exit at the top. Minimum external surface area, minimum mixing of cold with that already heated, maximum insulation. That is why in every other application they are made that way. 

Once you start mounting them on their side etc it is a compromise,

That's exactly what was fitted on Swan Radiance. It had a small airing cupboard with a tall domestic size tank. It had a thick insulation coating. Gallons of hot water which kept hot for ages. Cost more initially but well worth the investment. 

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Oh dear, this for me raises a thousand and one extra questions, like How near must a calorifier be to the engine? Can a standard domestic hot water tank be converted to a calorifier? Can a standard domestic hot water tank be fed from a calorifier automatically (thus acting like an extension hot tank)

Those will do for starters!

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A standard hot water tank IS a calorifier.

Mine has a fair trail to the engine and works fine, only thing is you can thermosyphon heat back to the engine when stopped causing it to cool faster, my starboard engine alway warms up quicker after a night plugged in as it's warmer to start with, not sure how to get round this without having to shut valves each time.

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Please hold in mind that I'm coming from a point of having no knowledge or understanding of how these things work.

I can think of only two heat sources for the calorifier, the exhaust system or the direct coolant. Which ever one it is, I've often wondered about harvesting the heat from the other, but that's for another day.

First question then, Given the space being available, how easy is it to convert a domestic hot water tank to marine use? 

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A domestic cylinder usually i believe has 3/4" dia coils a boat has 1/2 inch coils, boat ones have a base connector/flange to hold down domestic are free standing, boat ones have higher pressure strength and made heavier to with stand vibration SOME domestic ones have lower pressure rating  SOME domestic cylinders have thicker insulation which makes them more bulky to fit in a boat, BUT other than that i don't know of any reason why you can't physically fit one. and as to how near/far you can fit one the longer the hose FROM the ENGINE the more resistance and lower flow rate it will be,   on supply this will be pumped so only issue is how much do you run through the tap before you get hot water unless you fit a Johnson circulating pump in which case instant hot water at the same temp as tank. John

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I believe that the domestic tank we are talking about here is known as an indirect tank. That means that it is filled from a header tank rather than directly off mains pressure. Because boat domestic water systems are pressurised, including hot water, these domestic tanks have a habit of gradually 'ballooning' if used on a boats system. 

That's why homes with an indirect hot water cylinder and header tank in the loft (usually) have a lower pressure at the hot tap than the cold tap which is connected directly to the pressurised mains.

Having said that, you can use a domestic indirect tank on your boat  if you can reduce the input pressure (from your cold water pump) to about 12-15 psi. 

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Ricko's built a few boats such as Broads Sunrise a while back which had the Morco style gas combi boilers.

They've since been retrofitted with conventional systems so I'm not sure what happened but I guess they were too much trouble? It always seemed like a good idea to me, but of course they're reliant on the batteries for ignition, pumping and control.

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21 hours ago, oldgregg said:

Ricko's built a few boats such as Broads Sunrise a while back which had the Morco style gas combi boilers.

They've since been retrofitted with conventional systems so I'm not sure what happened but I guess they were too much trouble? It always seemed like a good idea to me, but of course they're reliant on the batteries for ignition, pumping and control.

Suncharm was the same, you are correct they were having problems with the system so it was changed. We never suffered any problems and the instant hot water was a blessing on chilly mornings. 

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