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water tank freeze?


MRBear

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I'd be more concerned about leaving electric heaters unattended long term, many are not designed for constant use and constitute a fire hazard. 

 Our last boat had an integral bow tank and we had cat ice on the surface probably twice in 16 years, and only after a prolonged cold period and temperatures of minus 8 and below. The risk of freezing is increased by the duration of the cold spell, not just low temperature alone. 

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Its all the little pipes and fiddly flush thingys that freeze in toilet systems. We have a vacuflush with a water valve that I always wrap an old blanket around, I also wrap a blanket or two around the raw water inlet for the engine cooling water, its turned off obviously but there is still a frost hazard.

Edited by Bee
awful spelling.
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1 minute ago, Bee said:

Its all the little pipes and fiddly flush thingys that freeze in toilet systems. We have a vacuflush with a water valve that I always wrap an old blanket around, I also wrap a blanket or two around the raw water inlet for the engine cooling water.

That does certainly delay the onset of damage, but unless you use 'electric blankets' any wrappings will just reach the ambient temperature anyway - maybe just a day later than they would have done if not wrapped.

 

6 minutes ago, BWM said:

I'd be more concerned about leaving electric heaters unattended long term, many are not designed for constant use and constitute a fire hazard. 

I use 2x tubular, 6 foot long, Greenhouse heaters that are designed to be on 'permanently'. Brackets screwed down so cannot fall over.

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56 minutes ago, Bee said:

Its all the little pipes and fiddly flush thingys that freeze in toilet systems. We have a vacuflush with a water valve that I always wrap an old blanket around, I also wrap a blanket or two around the raw water inlet for the engine cooling water, its turned off obviously but there is still a frost hazard.

 

Lot's of people think insulation by itself will prevent freezing pipes. It won't. The second law of thermodynamics dictates that all things tend towards equilibrium which means that without some sort of heat source, after a certain amount of time at sub-zero temperatures the water in the pipes will be at the same temperature as the ambient air on the other side of the insulation. Even the best insulation still allows heat transfer, it just reduces the rate (extends the time) of that transfer.

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59 minutes ago, Alan de Enfield said:

That does certainly delay the onset of damage, but unless you use 'electric blankets' any wrappings will just reach the ambient temperature anyway - maybe just a day later than they would have done if not wrapped.

 

I use 2x tubular, 6 foot long, Greenhouse heaters that are designed to be on 'permanently'. Brackets screwed down so cannot fall over.

A better option than most portable electric heaters, which are responsible for more than a few house fires, i think the op had one of those of the two they were using. They are still designed for a non flammable outbuilding though, so unsure how insurers would react if the worst happened.  

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4 minutes ago, BWM said:

A better option than most portable electric heaters, which are responsible for more than a few house fires, i think the op had one of those of the two they were using. They are still designed for a non flammable outbuilding though, so unsure how insurers would react if the worst happened.  

I have 2 X 125 watt of these tubular heaters and before using them on the boat I emailed my insurers (Newton Crum) with details of them including pictures. They replied they are fine to use as long as they are installed to the manufacturers instructions ie. screwed down. Been using them for several years now with no problems.

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1 hour ago, blackrose said:

 

Lot's of people think insulation by itself will prevent freezing pipes. It won't. The second law of thermodynamics dictates that all things tend towards equilibrium which means that without some sort of heat source, after a certain amount of time at sub-zero temperatures the water in the pipes will be at the same temperature as the ambient air on the other side of the insulation. Even the best insulation still allows heat transfer, it just reduces the rate (extends the time) of that transfer.

yeah but ...........................  whilst what you say is perfectly correct, in the event of a short sharp frost followed by a sunny mild day the insulation  will slow down the approach to equilibrium, so the temperature of the water will be perhaps 6 degrees plus or minus 4 degrees over a typical day, whilst without any insulation it could be 6 degrees plus or minus 8 degrees.  Therein lies the problem.  

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47 minutes ago, tosher said:

I have 2 X 125 watt of these tubular heaters and before using them on the boat I emailed my insurers (Newton Crum) with details of them including pictures. They replied they are fine to use as long as they are installed to the manufacturers instructions ie. screwed down. Been using them for several years now with no problems.

That's good to know, i have thought about installing one under the dry sump of my engine to make it easier to start in winter. 

 Alan seems well researched so i suspected they might be!

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18 minutes ago, BWM said:

That's good to know, i have thought about installing one under the dry sump of my engine to make it easier to start in winter. 

 Alan seems well researched so i suspected they might be!

That is what majority of cars in Sweden have, and for exactly that reason. Temps of minus 20 to minus 40 tends to 'thicken the oil' and tighten up the engine.

An extension lead plugged into an outside wall runs to an electric heater in the engine bay, and usually a small fan-heater in the passenger foot well as well.

 

Mine (on the boat) run down the 'outboard' side of each engine and the fixing brackets screw into the engine bearers, so just a matter of inches from the engine(s) sump.

 

Starboard side.

Heaters 1.jpg

Edited by Alan de Enfield
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I installed a coolant heater with integral water pump in my Peugeot diesel many years ago, I also cobbled together a micro switch on the fuel pump, once it had reached operating temp it switched on the cabin heater motor, all defrosted and cosy + instant starting. 

Edited by nb Innisfree
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4 hours ago, Alan de Enfield said:

 

I just pour a 'generous amount' of salt down each plug hole and then the toilets.

 

It costs pennies for big containers from the likes of Aldi

Genius. I love simple solutions!

4 hours ago, Alan de Enfield said:

 

I just pour a 'generous amount' of salt down each plug hole and then the toilets.

 

It costs pennies for big containers from the likes of Aldi

Genius. I love simple solutions!

4 hours ago, Alan de Enfield said:

 

I just pour a 'generous amount' of salt down each plug hole and then the toilets.

 

It costs pennies for big containers from the likes of Aldi

Genius. I love simple solutions!

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from now on i will be doing a full fresh water tank drain, turning off the tank tap, leaving my taps and shower open, and I've now set my wall mounted electric heater to frost mode(7c). the greenhouse heater is next to get for the engine bay.

 

as always, thanks guys, your advice is invaluable to us newbies, happy new year

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7 hours ago, MRBear said:

from now on i will be doing a full fresh water tank drain, turning off the tank tap, leaving my taps and shower open, and I've now set my wall mounted electric heater to frost mode(7c). the greenhouse heater is next to get for the engine bay.

 

as always, thanks guys, your advice is invaluable to us newbies, happy new year

If you turn up to spend time on the boat after draining the tank remember to take along a few litres of drinking water in case the water tap on the bank is frozen or has been isolated to prevent frost damage. 

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1 hour ago, alias said:

If you turn up to spend time on the boat after draining the tank remember to take along a few litres of drinking water in case the water tap on the bank is frozen or has been isolated to prevent frost damage. 

And a spare toilet in case that has frozen too, and a spare battery, 25 ltrs of diesel, a bottle of gas and some coal in case someone's nicked yours, and some dry matches, and a duvet in case yours is damp, etc, etc...  :giggles:

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3 hours ago, Sea Dog said:

And a spare toilet in case that has frozen too, and a spare battery, 25 ltrs of diesel, a bottle of gas and some coal in case someone's nicked yours, and some dry matches, and a duvet in case yours is damp, etc, etc...  :giggles:

and a boat in case some lockkeeper has sunk yours.

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22 minutes ago, cuthound said:

I leave my water tank about half full over winter, so it has room for expansion if it freezes, yet is ready to go cruising at a moments notice.

 

It hasn't caused any issues in the 7 years I have had the boat.

Same here. When I worked Offshore we had a layer of ice inside the cold water storage tanks about 8" thick, the tanks were standing on an open deck about 40 foot above the sea and none suffered damage.

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On 28/12/2020 at 13:38, Murflynn said:

yeah but ...........................  whilst what you say is perfectly correct, in the event of a short sharp frost followed by a sunny mild day the insulation  will slow down the approach to equilibrium, so the temperature of the water will be perhaps 6 degrees plus or minus 4 degrees over a typical day, whilst without any insulation it could be 6 degrees plus or minus 8 degrees.  Therein lies the problem.  

 

That's right. As I said, insulation will retard heat transfer but it won't stop it. If it slows down the rate of heat transfer and prevents pipes, etc from freezing before the ambient temperature happens to increase later that's all well and good. The problem is that many people mistakenly believe that insulation by itself will prevent pipes from freezing indefinitely even in prolonged sub-zero ambient temperatures and so fail to take other measures to prevent it.

Edited by blackrose
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13 hours ago, MRBear said:

from now on i will be doing a full fresh water tank drain, turning off the tank tap, leaving my taps and shower open, and I've now set my wall mounted electric heater to frost mode(7c). the greenhouse heater is next to get for the engine bay.

 

as always, thanks guys, your advice is invaluable to us newbies, happy new year

 

Why do you need to completely drain your tank and how are you going to do it? If you have a lot of water in the tank it's a lot of work for the pump to drain it all out in one go. Plus I can't help thinking that if you fail to drain it completely and happen to leave a little bit in there it's actually more likely to freeze than a big mass of water. It could freeze in the tank outlet and rupture it so that when you go to fill it up you flood the boat. 

 

In more than 18 years of living on boats I've yet to experience a frozen water tank and never heard of it on anyone else's boat.

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On 04/01/2021 at 07:11, MRBear said:

from now on i will be doing a full fresh water tank drain, turning off the tank tap, leaving my taps and shower open, and I've now set my wall mounted electric heater to frost mode(7c). the greenhouse heater is next to get for the engine bay.

 

as always, thanks guys, your advice is invaluable to us newbies, happy new year

If your tank is entirely below canal water level -- which many are -- then you don't have to worry about it freezing, no matter how long it's left unattended/unheated, because the water under/around the boat will never drop below +4C even if there is ice on the surface of the canal, so the water in the tank will never drop below this either. Water always freezes downwards starting from the surface because +4C is when it reaches maximum density, if cooled below this it becomes less dense so rises and sits on top of the +4C water.

 

If a large part of the tank is above water level (e.g. in the pointy bit of the bows) then this could start to freeze from the top down if there's a long enough stretch of subzero weather, but so long as there's enough expansion/air space above the water (tank is less than 90% full) this is unlikely to damage the tank, though not impossible if it's stainless or plastic -- an integral steel tank is very unlikely to be damaged.

 

Without any heating water pipes and fittings have a much bigger risk of freezing than the tank, if the air around them is subzero for long enough (depends on insulation -- could be only a few hours?) they will freeze, and this can split pipes or push joints apart leading to a leak when everything thaws, just like in a house -- I lost a bedroom ceiling that way, even though the pipes in the loft were lagged they froze when we were away over Xmas with the heating off.

 

Insulation will delay the freezing but not stop it, if it's subzero for several days water pipes will still freeze (see above). The engine cooling circuit won't freeze because it will have plenty of antifreeze in it, and if you have antifreeze in it (some do, some don't) neither will any boat heating/radiators, but any freshwater circuits (hot or cold water) can freeze.

 

If there's no background heating to keep the air above zero, this is a good reason to drain the tank -- not because the tank will freeze/split, but to stop the tank emptying itself through a split pipe or fitting when the thaw happens.

 

So if you're really worried about all this when away from the boat, the options are either install background heating or completely drain both cold and hot water systems.

Edited by IanD
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