Hi Helen,  Our house is unoccupied for periods during the winter so I filled the heating system with an antifreeze/rust inhibitor added to the water. If you drain out the water, measuring the volume of water that you drain out, you can work out the amount of antifreeze to add to give you the desired level of protection. I seem to remember that mine was one third antifreeze to two thirds water to give me protection against freezing down to minus 25C. The product i used was Sentinel X500 but there are many available.

Michael

You don't really need antifreeze in a heating system unless parts of it are outdoors or you have a mobile home.

I am assuming that you have at least a couple of electric radiators set on frost protection to stop your normal water pipes from freezing.

That is great advice Michael and I will follow your instruction to the letter, not that we have temperatures down to minus 25 in Brittany but I use the antifreeze in our UK radiators, again not for the antifreeze but it reduces noise in the pipes and give protection to the metal radiators from rusting.

Hi annabellespapa, You can of course vary the level of protection you need by adjusting the concentration of the antifreeze. We had had our house for several years when we arrived one winter and found all the cast iron radiators had cracked. I always drained the water pipes but didn't think about the heating system. I suppose I assumed that as they had been alright so far there would be no problem. This particularly cold winter our neighbour told us that a temperature of minus 20C had been recorded in the village, down by the river. I fitted all new radiators and replaced all the old steel pipes with copper.

Draining the system is an option, but as we visit our house a couple of times during the period when freezing temperatures are likely, it is a lot of trouble to keep draining then refilling the system, bleeding all the radiators several times and topping up the water.

I remember the antifreeze wasn't cheap, but compared to the cost of replacing all the radiators and pipework it was worth it for peace of mind.

Michael

Apart from the cost I don't see any harm in adding a correct amount of CH antifreeze.  From my experience in the trade in UK they always used a product on all new installations.  As mentioned earlier the modern steel radiators are the most vulnerable as well as any couplings or junctions where dissimilar metals are in contact.  

Another solution was suggested to me by a very clever bod (lots of letters after his name incl. a masters degree in mechanical engineering) was when he went back to UK for any length of time in winter he had installed a simple timer to switch on the circulating pump.  Set to run the pump for about 15 minutes two or three times a day when the thermostat sensed any risk of freezing.  Apparently there is no need to allow the boiler to fire up.  Just making the cold water circulate is enough to prevent freezing in all but the most extreme freezing weather.

Another tip for houses that are left unoccupied for long periods:  The water traps on sinks, showers, and wash basins can dry out allowing drain smells to come into the house.  (Yuck!) but can be prevented by pouring a small amount of cooking oil down each drain.  The oil stays on top of the water and stops it evaporating.

The cooking oil is a great idea, we sometimes get flies in the toilet closest to the fosse, I think the cooking all would sort that out.

When half the house was single glazed we used a dehumidifier on a timer to eject any condensation out of the house when we were not there,  worked really well until I left the downstairs toilet door open, no only did it dry out the u bend on the sink but we were just hours away from emptying the u bend on the toilet, that would of been a disaster !

Kitchen fats often solidify when they get cold.  This is what causes blockage problems.  Cooking oil used in moderation won't cause any bother.  A tiny amount is enough.