Re: Glycerin in the fresh water tank over winter

This discussion has been in Finnish boat news group shortly
(sfnet.harrastus.veneet, Painevesijärjestelmän talvisäilytys, 28.10.2005,
oh4gr). I've been using glycerin several years and it works well in
temperature down to - 25 C or even more. The good thing is that when
glycerin-water mixture freezes, it will not form hard ice breaking the pipes
but a slush which is soft.

First you empty the fresh water tank and feed line to fresh water pump. Then
you blow the pipe work empty with pressurized air (carefully) and empty any
hot water tank in the system. If you have a suction system (like peristaltic
pump), you can draw the pipes empty through the tap side.

Then you pump glycerin water mixture through the pipe work, e.g. the volume
needed is small (one to two liters). You leave the mixture to pipes and in
spring flush the pipes with fresh water. (Glycerin is edible and there is no
danger if the flushing is not through.) Emptying the pipes before winter
with pressurized air or suction is typically not 100% effecient and there
are some pockets of water left in pipe corners and they freeze and burst the
pipe during winter frost. Therefore using glycerin-water as a cryo-liquid is
preferrable.

NOTE: Glycerin in not glycol. Glycol (used in engine block anti-freeze) is
POISONOUS!!!! Do not get confuced. Pharmacies sell glycerol. Prize range for
food grade 85 % glycerin is around 30 ?/L, but you need only 1 ... 2 L.

I small note from Google search:
Like pure water, the cryoprotectant glycerol has a freezing temperature
which is close to 0ºC, but mixtures of glycerol & water freeze at lower
temperatures. A 50% w/w (weight/weight) solution of glycerol has a
freezing/melting temperature (Tm) of -23ºC. The mixture with the lowest
freezing temperature is roughly 66% glycerol, freezing at about -46ºC.
(http://www.benbest.com/cryonics/cooling.html)

Wallu


"Phil R" <ditchcrawler@xxxxxxxxx> wrote in message
news:j72dndzmjuil_-fenZ2dnUVZ8qqdnZ2d@xxxxxxxxxxxx
>
> "NB Harry" <Matt@xxxxxxxxxxxxx> wrote in message
> news:1132074950.335641.68440@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > Hi all,
> >
> > We are starting to think about winterising our narrowboat for the
> first
> > year ever, as up until now we have been live aboards.
> >
> > Does anyone have any ideas on adding Glycerin (common food additive)
> to
> > the fresh water tank? We have searched on Google and found nothing
> at
> > all - but to us it sounds like a reasonable idea.
> >
> > Mixed around 1 part to 3 parts water, this should have a freezing
> point
> > well below any sustained temperatures we may get in the south of
> > England. It is also non-toxic - which would mean if we use the
> > narrowboat over winter we can still take a shower! (though perhaps
> not
> > a cup of tea...)
> >
> > We were just thinking of dropping the water tank level, adding the
> > glycerin and running all the taps for a little while.
> >
> > Anyway, my questions are:
> > 1) Is this a stupid idea?
> > 2) It lowers the freezing point, but Im not sure about the "burst
> > point" or whatever its called. I.e., will it still expand and cause
> > bursting?
> > 3) Could it all go horribly wrong and clog up all the pipes?
> >
> > Thanks for any advice. I expect we may just drain the calorifier and
> > leave the taps open like people seem to suggest. However, all the
> pipes
> > are copper, so Im worried this may not be enough,
>
> Matt
> A few comments/suggestions:
> Adding glycerine, or anything else, to the tank sounds an expensive
> option in the quantity you might need - and it might taint the water?
>
> The main components most vulnerable to frost damage will be
> gas water heaters and calorifiers + pipework. IMHO any freshwater
> system on a boat should be designed so that it can be drained from
> the lowest point. If you haven't got a drain point I suggest you fit
> one. The safest option will then be to close the valve at the bottom
> of the tank, open all taps and drain off points and then run the pump.
> A properly designed system should then result in fully drained
> pipework and vulnerable parts. Whether or not you decide to drain
> the whole contents of the water tank will depend upon the construction
> and shape of the tank. If the tank is in the bow and follows the shape
> of the bow you should be OK - as an added precaution you could
> float a foam/polystyrene ball to absorb any expansion?
>
> Cheers
> Phil
> (must remember to drain our water system this weekend!)
>
>


.

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